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Diffstat (limited to 'fs/locks.c')
| -rw-r--r-- | fs/locks.c | 2939 |
1 files changed, 2939 insertions, 0 deletions
diff --git a/fs/locks.c b/fs/locks.c new file mode 100644 index 000000000..1047ab2b1 --- /dev/null +++ b/fs/locks.c @@ -0,0 +1,2939 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * linux/fs/locks.c + * + * We implement four types of file locks: BSD locks, posix locks, open + * file description locks, and leases. For details about BSD locks, + * see the flock(2) man page; for details about the other three, see + * fcntl(2). + * + * + * Locking conflicts and dependencies: + * If multiple threads attempt to lock the same byte (or flock the same file) + * only one can be granted the lock, and other must wait their turn. + * The first lock has been "applied" or "granted", the others are "waiting" + * and are "blocked" by the "applied" lock.. + * + * Waiting and applied locks are all kept in trees whose properties are: + * + * - the root of a tree may be an applied or waiting lock. + * - every other node in the tree is a waiting lock that + * conflicts with every ancestor of that node. + * + * Every such tree begins life as a waiting singleton which obviously + * satisfies the above properties. + * + * The only ways we modify trees preserve these properties: + * + * 1. We may add a new leaf node, but only after first verifying that it + * conflicts with all of its ancestors. + * 2. We may remove the root of a tree, creating a new singleton + * tree from the root and N new trees rooted in the immediate + * children. + * 3. If the root of a tree is not currently an applied lock, we may + * apply it (if possible). + * 4. We may upgrade the root of the tree (either extend its range, + * or upgrade its entire range from read to write). + * + * When an applied lock is modified in a way that reduces or downgrades any + * part of its range, we remove all its children (2 above). This particularly + * happens when a lock is unlocked. + * + * For each of those child trees we "wake up" the thread which is + * waiting for the lock so it can continue handling as follows: if the + * root of the tree applies, we do so (3). If it doesn't, it must + * conflict with some applied lock. We remove (wake up) all of its children + * (2), and add it is a new leaf to the tree rooted in the applied + * lock (1). We then repeat the process recursively with those + * children. + * + */ + +#include <linux/capability.h> +#include <linux/file.h> +#include <linux/fdtable.h> +#include <linux/fs.h> +#include <linux/init.h> +#include <linux/security.h> +#include <linux/slab.h> +#include <linux/syscalls.h> +#include <linux/time.h> +#include <linux/rcupdate.h> +#include <linux/pid_namespace.h> +#include <linux/hashtable.h> +#include <linux/percpu.h> +#include <linux/sysctl.h> + +#define CREATE_TRACE_POINTS +#include <trace/events/filelock.h> + +#include <linux/uaccess.h> + +#define IS_POSIX(fl) (fl->fl_flags & FL_POSIX) +#define IS_FLOCK(fl) (fl->fl_flags & FL_FLOCK) +#define IS_LEASE(fl) (fl->fl_flags & (FL_LEASE|FL_DELEG|FL_LAYOUT)) +#define IS_OFDLCK(fl) (fl->fl_flags & FL_OFDLCK) +#define IS_REMOTELCK(fl) (fl->fl_pid <= 0) + +static bool lease_breaking(struct file_lock *fl) +{ + return fl->fl_flags & (FL_UNLOCK_PENDING | FL_DOWNGRADE_PENDING); +} + +static int target_leasetype(struct file_lock *fl) +{ + if (fl->fl_flags & FL_UNLOCK_PENDING) + return F_UNLCK; + if (fl->fl_flags & FL_DOWNGRADE_PENDING) + return F_RDLCK; + return fl->fl_type; +} + +static int leases_enable = 1; +static int lease_break_time = 45; + +#ifdef CONFIG_SYSCTL +static struct ctl_table locks_sysctls[] = { + { + .procname = "leases-enable", + .data = &leases_enable, + .maxlen = sizeof(int), + .mode = 0644, + .proc_handler = proc_dointvec, + }, +#ifdef CONFIG_MMU + { + .procname = "lease-break-time", + .data = &lease_break_time, + .maxlen = sizeof(int), + .mode = 0644, + .proc_handler = proc_dointvec, + }, +#endif /* CONFIG_MMU */ + {} +}; + +static int __init init_fs_locks_sysctls(void) +{ + register_sysctl_init("fs", locks_sysctls); + return 0; +} +early_initcall(init_fs_locks_sysctls); +#endif /* CONFIG_SYSCTL */ + +/* + * The global file_lock_list is only used for displaying /proc/locks, so we + * keep a list on each CPU, with each list protected by its own spinlock. + * Global serialization is done using file_rwsem. + * + * Note that alterations to the list also require that the relevant flc_lock is + * held. + */ +struct file_lock_list_struct { + spinlock_t lock; + struct hlist_head hlist; +}; +static DEFINE_PER_CPU(struct file_lock_list_struct, file_lock_list); +DEFINE_STATIC_PERCPU_RWSEM(file_rwsem); + + +/* + * The blocked_hash is used to find POSIX lock loops for deadlock detection. + * It is protected by blocked_lock_lock. + * + * We hash locks by lockowner in order to optimize searching for the lock a + * particular lockowner is waiting on. + * + * FIXME: make this value scale via some heuristic? We generally will want more + * buckets when we have more lockowners holding locks, but that's a little + * difficult to determine without knowing what the workload will look like. + */ +#define BLOCKED_HASH_BITS 7 +static DEFINE_HASHTABLE(blocked_hash, BLOCKED_HASH_BITS); + +/* + * This lock protects the blocked_hash. Generally, if you're accessing it, you + * want to be holding this lock. + * + * In addition, it also protects the fl->fl_blocked_requests list, and the + * fl->fl_blocker pointer for file_lock structures that are acting as lock + * requests (in contrast to those that are acting as records of acquired locks). + * + * Note that when we acquire this lock in order to change the above fields, + * we often hold the flc_lock as well. In certain cases, when reading the fields + * protected by this lock, we can skip acquiring it iff we already hold the + * flc_lock. + */ +static DEFINE_SPINLOCK(blocked_lock_lock); + +static struct kmem_cache *flctx_cache __read_mostly; +static struct kmem_cache *filelock_cache __read_mostly; + +static struct file_lock_context * +locks_get_lock_context(struct inode *inode, int type) +{ + struct file_lock_context *ctx; + + /* paired with cmpxchg() below */ + ctx = smp_load_acquire(&inode->i_flctx); + if (likely(ctx) || type == F_UNLCK) + goto out; + + ctx = kmem_cache_alloc(flctx_cache, GFP_KERNEL); + if (!ctx) + goto out; + + spin_lock_init(&ctx->flc_lock); + INIT_LIST_HEAD(&ctx->flc_flock); + INIT_LIST_HEAD(&ctx->flc_posix); + INIT_LIST_HEAD(&ctx->flc_lease); + + /* + * Assign the pointer if it's not already assigned. If it is, then + * free the context we just allocated. + */ + if (cmpxchg(&inode->i_flctx, NULL, ctx)) { + kmem_cache_free(flctx_cache, ctx); + ctx = smp_load_acquire(&inode->i_flctx); + } +out: + trace_locks_get_lock_context(inode, type, ctx); + return ctx; +} + +static void +locks_dump_ctx_list(struct list_head *list, char *list_type) +{ + struct file_lock *fl; + + list_for_each_entry(fl, list, fl_list) { + pr_warn("%s: fl_owner=%p fl_flags=0x%x fl_type=0x%x fl_pid=%u\n", list_type, fl->fl_owner, fl->fl_flags, fl->fl_type, fl->fl_pid); + } +} + +static void +locks_check_ctx_lists(struct inode *inode) +{ + struct file_lock_context *ctx = inode->i_flctx; + + if (unlikely(!list_empty(&ctx->flc_flock) || + !list_empty(&ctx->flc_posix) || + !list_empty(&ctx->flc_lease))) { + pr_warn("Leaked locks on dev=0x%x:0x%x ino=0x%lx:\n", + MAJOR(inode->i_sb->s_dev), MINOR(inode->i_sb->s_dev), + inode->i_ino); + locks_dump_ctx_list(&ctx->flc_flock, "FLOCK"); + locks_dump_ctx_list(&ctx->flc_posix, "POSIX"); + locks_dump_ctx_list(&ctx->flc_lease, "LEASE"); + } +} + +static void +locks_check_ctx_file_list(struct file *filp, struct list_head *list, + char *list_type) +{ + struct file_lock *fl; + struct inode *inode = locks_inode(filp); + + list_for_each_entry(fl, list, fl_list) + if (fl->fl_file == filp) + pr_warn("Leaked %s lock on dev=0x%x:0x%x ino=0x%lx " + " fl_owner=%p fl_flags=0x%x fl_type=0x%x fl_pid=%u\n", + list_type, MAJOR(inode->i_sb->s_dev), + MINOR(inode->i_sb->s_dev), inode->i_ino, + fl->fl_owner, fl->fl_flags, fl->fl_type, fl->fl_pid); +} + +void +locks_free_lock_context(struct inode *inode) +{ + struct file_lock_context *ctx = inode->i_flctx; + + if (unlikely(ctx)) { + locks_check_ctx_lists(inode); + kmem_cache_free(flctx_cache, ctx); + } +} + +static void locks_init_lock_heads(struct file_lock *fl) +{ + INIT_HLIST_NODE(&fl->fl_link); + INIT_LIST_HEAD(&fl->fl_list); + INIT_LIST_HEAD(&fl->fl_blocked_requests); + INIT_LIST_HEAD(&fl->fl_blocked_member); + init_waitqueue_head(&fl->fl_wait); +} + +/* Allocate an empty lock structure. */ +struct file_lock *locks_alloc_lock(void) +{ + struct file_lock *fl = kmem_cache_zalloc(filelock_cache, GFP_KERNEL); + + if (fl) + locks_init_lock_heads(fl); + + return fl; +} +EXPORT_SYMBOL_GPL(locks_alloc_lock); + +void locks_release_private(struct file_lock *fl) +{ + BUG_ON(waitqueue_active(&fl->fl_wait)); + BUG_ON(!list_empty(&fl->fl_list)); + BUG_ON(!list_empty(&fl->fl_blocked_requests)); + BUG_ON(!list_empty(&fl->fl_blocked_member)); + BUG_ON(!hlist_unhashed(&fl->fl_link)); + + if (fl->fl_ops) { + if (fl->fl_ops->fl_release_private) + fl->fl_ops->fl_release_private(fl); + fl->fl_ops = NULL; + } + + if (fl->fl_lmops) { + if (fl->fl_lmops->lm_put_owner) { + fl->fl_lmops->lm_put_owner(fl->fl_owner); + fl->fl_owner = NULL; + } + fl->fl_lmops = NULL; + } +} +EXPORT_SYMBOL_GPL(locks_release_private); + +/** + * locks_owner_has_blockers - Check for blocking lock requests + * @flctx: file lock context + * @owner: lock owner + * + * Return values: + * %true: @owner has at least one blocker + * %false: @owner has no blockers + */ +bool locks_owner_has_blockers(struct file_lock_context *flctx, + fl_owner_t owner) +{ + struct file_lock *fl; + + spin_lock(&flctx->flc_lock); + list_for_each_entry(fl, &flctx->flc_posix, fl_list) { + if (fl->fl_owner != owner) + continue; + if (!list_empty(&fl->fl_blocked_requests)) { + spin_unlock(&flctx->flc_lock); + return true; + } + } + spin_unlock(&flctx->flc_lock); + return false; +} +EXPORT_SYMBOL_GPL(locks_owner_has_blockers); + +/* Free a lock which is not in use. */ +void locks_free_lock(struct file_lock *fl) +{ + locks_release_private(fl); + kmem_cache_free(filelock_cache, fl); +} +EXPORT_SYMBOL(locks_free_lock); + +static void +locks_dispose_list(struct list_head *dispose) +{ + struct file_lock *fl; + + while (!list_empty(dispose)) { + fl = list_first_entry(dispose, struct file_lock, fl_list); + list_del_init(&fl->fl_list); + locks_free_lock(fl); + } +} + +void locks_init_lock(struct file_lock *fl) +{ + memset(fl, 0, sizeof(struct file_lock)); + locks_init_lock_heads(fl); +} +EXPORT_SYMBOL(locks_init_lock); + +/* + * Initialize a new lock from an existing file_lock structure. + */ +void locks_copy_conflock(struct file_lock *new, struct file_lock *fl) +{ + new->fl_owner = fl->fl_owner; + new->fl_pid = fl->fl_pid; + new->fl_file = NULL; + new->fl_flags = fl->fl_flags; + new->fl_type = fl->fl_type; + new->fl_start = fl->fl_start; + new->fl_end = fl->fl_end; + new->fl_lmops = fl->fl_lmops; + new->fl_ops = NULL; + + if (fl->fl_lmops) { + if (fl->fl_lmops->lm_get_owner) + fl->fl_lmops->lm_get_owner(fl->fl_owner); + } +} +EXPORT_SYMBOL(locks_copy_conflock); + +void locks_copy_lock(struct file_lock *new, struct file_lock *fl) +{ + /* "new" must be a freshly-initialized lock */ + WARN_ON_ONCE(new->fl_ops); + + locks_copy_conflock(new, fl); + + new->fl_file = fl->fl_file; + new->fl_ops = fl->fl_ops; + + if (fl->fl_ops) { + if (fl->fl_ops->fl_copy_lock) + fl->fl_ops->fl_copy_lock(new, fl); + } +} +EXPORT_SYMBOL(locks_copy_lock); + +static void locks_move_blocks(struct file_lock *new, struct file_lock *fl) +{ + struct file_lock *f; + + /* + * As ctx->flc_lock is held, new requests cannot be added to + * ->fl_blocked_requests, so we don't need a lock to check if it + * is empty. + */ + if (list_empty(&fl->fl_blocked_requests)) + return; + spin_lock(&blocked_lock_lock); + list_splice_init(&fl->fl_blocked_requests, &new->fl_blocked_requests); + list_for_each_entry(f, &new->fl_blocked_requests, fl_blocked_member) + f->fl_blocker = new; + spin_unlock(&blocked_lock_lock); +} + +static inline int flock_translate_cmd(int cmd) { + switch (cmd) { + case LOCK_SH: + return F_RDLCK; + case LOCK_EX: + return F_WRLCK; + case LOCK_UN: + return F_UNLCK; + } + return -EINVAL; +} + +/* Fill in a file_lock structure with an appropriate FLOCK lock. */ +static void flock_make_lock(struct file *filp, struct file_lock *fl, int type) +{ + locks_init_lock(fl); + + fl->fl_file = filp; + fl->fl_owner = filp; + fl->fl_pid = current->tgid; + fl->fl_flags = FL_FLOCK; + fl->fl_type = type; + fl->fl_end = OFFSET_MAX; +} + +static int assign_type(struct file_lock *fl, long type) +{ + switch (type) { + case F_RDLCK: + case F_WRLCK: + case F_UNLCK: + fl->fl_type = type; + break; + default: + return -EINVAL; + } + return 0; +} + +static int flock64_to_posix_lock(struct file *filp, struct file_lock *fl, + struct flock64 *l) +{ + switch (l->l_whence) { + case SEEK_SET: + fl->fl_start = 0; + break; + case SEEK_CUR: + fl->fl_start = filp->f_pos; + break; + case SEEK_END: + fl->fl_start = i_size_read(file_inode(filp)); + break; + default: + return -EINVAL; + } + if (l->l_start > OFFSET_MAX - fl->fl_start) + return -EOVERFLOW; + fl->fl_start += l->l_start; + if (fl->fl_start < 0) + return -EINVAL; + + /* POSIX-1996 leaves the case l->l_len < 0 undefined; + POSIX-2001 defines it. */ + if (l->l_len > 0) { + if (l->l_len - 1 > OFFSET_MAX - fl->fl_start) + return -EOVERFLOW; + fl->fl_end = fl->fl_start + (l->l_len - 1); + + } else if (l->l_len < 0) { + if (fl->fl_start + l->l_len < 0) + return -EINVAL; + fl->fl_end = fl->fl_start - 1; + fl->fl_start += l->l_len; + } else + fl->fl_end = OFFSET_MAX; + + fl->fl_owner = current->files; + fl->fl_pid = current->tgid; + fl->fl_file = filp; + fl->fl_flags = FL_POSIX; + fl->fl_ops = NULL; + fl->fl_lmops = NULL; + + return assign_type(fl, l->l_type); +} + +/* Verify a "struct flock" and copy it to a "struct file_lock" as a POSIX + * style lock. + */ +static int flock_to_posix_lock(struct file *filp, struct file_lock *fl, + struct flock *l) +{ + struct flock64 ll = { + .l_type = l->l_type, + .l_whence = l->l_whence, + .l_start = l->l_start, + .l_len = l->l_len, + }; + + return flock64_to_posix_lock(filp, fl, &ll); +} + +/* default lease lock manager operations */ +static bool +lease_break_callback(struct file_lock *fl) +{ + kill_fasync(&fl->fl_fasync, SIGIO, POLL_MSG); + return false; +} + +static void +lease_setup(struct file_lock *fl, void **priv) +{ + struct file *filp = fl->fl_file; + struct fasync_struct *fa = *priv; + + /* + * fasync_insert_entry() returns the old entry if any. If there was no + * old entry, then it used "priv" and inserted it into the fasync list. + * Clear the pointer to indicate that it shouldn't be freed. + */ + if (!fasync_insert_entry(fa->fa_fd, filp, &fl->fl_fasync, fa)) + *priv = NULL; + + __f_setown(filp, task_pid(current), PIDTYPE_TGID, 0); +} + +static const struct lock_manager_operations lease_manager_ops = { + .lm_break = lease_break_callback, + .lm_change = lease_modify, + .lm_setup = lease_setup, +}; + +/* + * Initialize a lease, use the default lock manager operations + */ +static int lease_init(struct file *filp, long type, struct file_lock *fl) +{ + if (assign_type(fl, type) != 0) + return -EINVAL; + + fl->fl_owner = filp; + fl->fl_pid = current->tgid; + + fl->fl_file = filp; + fl->fl_flags = FL_LEASE; + fl->fl_start = 0; + fl->fl_end = OFFSET_MAX; + fl->fl_ops = NULL; + fl->fl_lmops = &lease_manager_ops; + return 0; +} + +/* Allocate a file_lock initialised to this type of lease */ +static struct file_lock *lease_alloc(struct file *filp, long type) +{ + struct file_lock *fl = locks_alloc_lock(); + int error = -ENOMEM; + + if (fl == NULL) + return ERR_PTR(error); + + error = lease_init(filp, type, fl); + if (error) { + locks_free_lock(fl); + return ERR_PTR(error); + } + return fl; +} + +/* Check if two locks overlap each other. + */ +static inline int locks_overlap(struct file_lock *fl1, struct file_lock *fl2) +{ + return ((fl1->fl_end >= fl2->fl_start) && + (fl2->fl_end >= fl1->fl_start)); +} + +/* + * Check whether two locks have the same owner. + */ +static int posix_same_owner(struct file_lock *fl1, struct file_lock *fl2) +{ + return fl1->fl_owner == fl2->fl_owner; +} + +/* Must be called with the flc_lock held! */ +static void locks_insert_global_locks(struct file_lock *fl) +{ + struct file_lock_list_struct *fll = this_cpu_ptr(&file_lock_list); + + percpu_rwsem_assert_held(&file_rwsem); + + spin_lock(&fll->lock); + fl->fl_link_cpu = smp_processor_id(); + hlist_add_head(&fl->fl_link, &fll->hlist); + spin_unlock(&fll->lock); +} + +/* Must be called with the flc_lock held! */ +static void locks_delete_global_locks(struct file_lock *fl) +{ + struct file_lock_list_struct *fll; + + percpu_rwsem_assert_held(&file_rwsem); + + /* + * Avoid taking lock if already unhashed. This is safe since this check + * is done while holding the flc_lock, and new insertions into the list + * also require that it be held. + */ + if (hlist_unhashed(&fl->fl_link)) + return; + + fll = per_cpu_ptr(&file_lock_list, fl->fl_link_cpu); + spin_lock(&fll->lock); + hlist_del_init(&fl->fl_link); + spin_unlock(&fll->lock); +} + +static unsigned long +posix_owner_key(struct file_lock *fl) +{ + return (unsigned long)fl->fl_owner; +} + +static void locks_insert_global_blocked(struct file_lock *waiter) +{ + lockdep_assert_held(&blocked_lock_lock); + + hash_add(blocked_hash, &waiter->fl_link, posix_owner_key(waiter)); +} + +static void locks_delete_global_blocked(struct file_lock *waiter) +{ + lockdep_assert_held(&blocked_lock_lock); + + hash_del(&waiter->fl_link); +} + +/* Remove waiter from blocker's block list. + * When blocker ends up pointing to itself then the list is empty. + * + * Must be called with blocked_lock_lock held. + */ +static void __locks_delete_block(struct file_lock *waiter) +{ + locks_delete_global_blocked(waiter); + list_del_init(&waiter->fl_blocked_member); +} + +static void __locks_wake_up_blocks(struct file_lock *blocker) +{ + while (!list_empty(&blocker->fl_blocked_requests)) { + struct file_lock *waiter; + + waiter = list_first_entry(&blocker->fl_blocked_requests, + struct file_lock, fl_blocked_member); + __locks_delete_block(waiter); + if (waiter->fl_lmops && waiter->fl_lmops->lm_notify) + waiter->fl_lmops->lm_notify(waiter); + else + wake_up(&waiter->fl_wait); + + /* + * The setting of fl_blocker to NULL marks the "done" + * point in deleting a block. Paired with acquire at the top + * of locks_delete_block(). + */ + smp_store_release(&waiter->fl_blocker, NULL); + } +} + +/** + * locks_delete_block - stop waiting for a file lock + * @waiter: the lock which was waiting + * + * lockd/nfsd need to disconnect the lock while working on it. + */ +int locks_delete_block(struct file_lock *waiter) +{ + int status = -ENOENT; + + /* + * If fl_blocker is NULL, it won't be set again as this thread "owns" + * the lock and is the only one that might try to claim the lock. + * + * We use acquire/release to manage fl_blocker so that we can + * optimize away taking the blocked_lock_lock in many cases. + * + * The smp_load_acquire guarantees two things: + * + * 1/ that fl_blocked_requests can be tested locklessly. If something + * was recently added to that list it must have been in a locked region + * *before* the locked region when fl_blocker was set to NULL. + * + * 2/ that no other thread is accessing 'waiter', so it is safe to free + * it. __locks_wake_up_blocks is careful not to touch waiter after + * fl_blocker is released. + * + * If a lockless check of fl_blocker shows it to be NULL, we know that + * no new locks can be inserted into its fl_blocked_requests list, and + * can avoid doing anything further if the list is empty. + */ + if (!smp_load_acquire(&waiter->fl_blocker) && + list_empty(&waiter->fl_blocked_requests)) + return status; + + spin_lock(&blocked_lock_lock); + if (waiter->fl_blocker) + status = 0; + __locks_wake_up_blocks(waiter); + __locks_delete_block(waiter); + + /* + * The setting of fl_blocker to NULL marks the "done" point in deleting + * a block. Paired with acquire at the top of this function. + */ + smp_store_release(&waiter->fl_blocker, NULL); + spin_unlock(&blocked_lock_lock); + return status; +} +EXPORT_SYMBOL(locks_delete_block); + +/* Insert waiter into blocker's block list. + * We use a circular list so that processes can be easily woken up in + * the order they blocked. The documentation doesn't require this but + * it seems like the reasonable thing to do. + * + * Must be called with both the flc_lock and blocked_lock_lock held. The + * fl_blocked_requests list itself is protected by the blocked_lock_lock, + * but by ensuring that the flc_lock is also held on insertions we can avoid + * taking the blocked_lock_lock in some cases when we see that the + * fl_blocked_requests list is empty. + * + * Rather than just adding to the list, we check for conflicts with any existing + * waiters, and add beneath any waiter that blocks the new waiter. + * Thus wakeups don't happen until needed. + */ +static void __locks_insert_block(struct file_lock *blocker, + struct file_lock *waiter, + bool conflict(struct file_lock *, + struct file_lock *)) +{ + struct file_lock *fl; + BUG_ON(!list_empty(&waiter->fl_blocked_member)); + +new_blocker: + list_for_each_entry(fl, &blocker->fl_blocked_requests, fl_blocked_member) + if (conflict(fl, waiter)) { + blocker = fl; + goto new_blocker; + } + waiter->fl_blocker = blocker; + list_add_tail(&waiter->fl_blocked_member, &blocker->fl_blocked_requests); + if (IS_POSIX(blocker) && !IS_OFDLCK(blocker)) + locks_insert_global_blocked(waiter); + + /* The requests in waiter->fl_blocked are known to conflict with + * waiter, but might not conflict with blocker, or the requests + * and lock which block it. So they all need to be woken. + */ + __locks_wake_up_blocks(waiter); +} + +/* Must be called with flc_lock held. */ +static void locks_insert_block(struct file_lock *blocker, + struct file_lock *waiter, + bool conflict(struct file_lock *, + struct file_lock *)) +{ + spin_lock(&blocked_lock_lock); + __locks_insert_block(blocker, waiter, conflict); + spin_unlock(&blocked_lock_lock); +} + +/* + * Wake up processes blocked waiting for blocker. + * + * Must be called with the inode->flc_lock held! + */ +static void locks_wake_up_blocks(struct file_lock *blocker) +{ + /* + * Avoid taking global lock if list is empty. This is safe since new + * blocked requests are only added to the list under the flc_lock, and + * the flc_lock is always held here. Note that removal from the + * fl_blocked_requests list does not require the flc_lock, so we must + * recheck list_empty() after acquiring the blocked_lock_lock. + */ + if (list_empty(&blocker->fl_blocked_requests)) + return; + + spin_lock(&blocked_lock_lock); + __locks_wake_up_blocks(blocker); + spin_unlock(&blocked_lock_lock); +} + +static void +locks_insert_lock_ctx(struct file_lock *fl, struct list_head *before) +{ + list_add_tail(&fl->fl_list, before); + locks_insert_global_locks(fl); +} + +static void +locks_unlink_lock_ctx(struct file_lock *fl) +{ + locks_delete_global_locks(fl); + list_del_init(&fl->fl_list); + locks_wake_up_blocks(fl); +} + +static void +locks_delete_lock_ctx(struct file_lock *fl, struct list_head *dispose) +{ + locks_unlink_lock_ctx(fl); + if (dispose) + list_add(&fl->fl_list, dispose); + else + locks_free_lock(fl); +} + +/* Determine if lock sys_fl blocks lock caller_fl. Common functionality + * checks for shared/exclusive status of overlapping locks. + */ +static bool locks_conflict(struct file_lock *caller_fl, + struct file_lock *sys_fl) +{ + if (sys_fl->fl_type == F_WRLCK) + return true; + if (caller_fl->fl_type == F_WRLCK) + return true; + return false; +} + +/* Determine if lock sys_fl blocks lock caller_fl. POSIX specific + * checking before calling the locks_conflict(). + */ +static bool posix_locks_conflict(struct file_lock *caller_fl, + struct file_lock *sys_fl) +{ + /* POSIX locks owned by the same process do not conflict with + * each other. + */ + if (posix_same_owner(caller_fl, sys_fl)) + return false; + + /* Check whether they overlap */ + if (!locks_overlap(caller_fl, sys_fl)) + return false; + + return locks_conflict(caller_fl, sys_fl); +} + +/* Determine if lock sys_fl blocks lock caller_fl. FLOCK specific + * checking before calling the locks_conflict(). + */ +static bool flock_locks_conflict(struct file_lock *caller_fl, + struct file_lock *sys_fl) +{ + /* FLOCK locks referring to the same filp do not conflict with + * each other. + */ + if (caller_fl->fl_file == sys_fl->fl_file) + return false; + + return locks_conflict(caller_fl, sys_fl); +} + +void +posix_test_lock(struct file *filp, struct file_lock *fl) +{ + struct file_lock *cfl; + struct file_lock_context *ctx; + struct inode *inode = locks_inode(filp); + void *owner; + void (*func)(void); + + ctx = smp_load_acquire(&inode->i_flctx); + if (!ctx || list_empty_careful(&ctx->flc_posix)) { + fl->fl_type = F_UNLCK; + return; + } + +retry: + spin_lock(&ctx->flc_lock); + list_for_each_entry(cfl, &ctx->flc_posix, fl_list) { + if (!posix_locks_conflict(fl, cfl)) + continue; + if (cfl->fl_lmops && cfl->fl_lmops->lm_lock_expirable + && (*cfl->fl_lmops->lm_lock_expirable)(cfl)) { + owner = cfl->fl_lmops->lm_mod_owner; + func = cfl->fl_lmops->lm_expire_lock; + __module_get(owner); + spin_unlock(&ctx->flc_lock); + (*func)(); + module_put(owner); + goto retry; + } + locks_copy_conflock(fl, cfl); + goto out; + } + fl->fl_type = F_UNLCK; +out: + spin_unlock(&ctx->flc_lock); + return; +} +EXPORT_SYMBOL(posix_test_lock); + +/* + * Deadlock detection: + * + * We attempt to detect deadlocks that are due purely to posix file + * locks. + * + * We assume that a task can be waiting for at most one lock at a time. + * So for any acquired lock, the process holding that lock may be + * waiting on at most one other lock. That lock in turns may be held by + * someone waiting for at most one other lock. Given a requested lock + * caller_fl which is about to wait for a conflicting lock block_fl, we + * follow this chain of waiters to ensure we are not about to create a + * cycle. + * + * Since we do this before we ever put a process to sleep on a lock, we + * are ensured that there is never a cycle; that is what guarantees that + * the while() loop in posix_locks_deadlock() eventually completes. + * + * Note: the above assumption may not be true when handling lock + * requests from a broken NFS client. It may also fail in the presence + * of tasks (such as posix threads) sharing the same open file table. + * To handle those cases, we just bail out after a few iterations. + * + * For FL_OFDLCK locks, the owner is the filp, not the files_struct. + * Because the owner is not even nominally tied to a thread of + * execution, the deadlock detection below can't reasonably work well. Just + * skip it for those. + * + * In principle, we could do a more limited deadlock detection on FL_OFDLCK + * locks that just checks for the case where two tasks are attempting to + * upgrade from read to write locks on the same inode. + */ + +#define MAX_DEADLK_ITERATIONS 10 + +/* Find a lock that the owner of the given block_fl is blocking on. */ +static struct file_lock *what_owner_is_waiting_for(struct file_lock *block_fl) +{ + struct file_lock *fl; + + hash_for_each_possible(blocked_hash, fl, fl_link, posix_owner_key(block_fl)) { + if (posix_same_owner(fl, block_fl)) { + while (fl->fl_blocker) + fl = fl->fl_blocker; + return fl; + } + } + return NULL; +} + +/* Must be called with the blocked_lock_lock held! */ +static int posix_locks_deadlock(struct file_lock *caller_fl, + struct file_lock *block_fl) +{ + int i = 0; + + lockdep_assert_held(&blocked_lock_lock); + + /* + * This deadlock detector can't reasonably detect deadlocks with + * FL_OFDLCK locks, since they aren't owned by a process, per-se. + */ + if (IS_OFDLCK(caller_fl)) + return 0; + + while ((block_fl = what_owner_is_waiting_for(block_fl))) { + if (i++ > MAX_DEADLK_ITERATIONS) + return 0; + if (posix_same_owner(caller_fl, block_fl)) + return 1; + } + return 0; +} + +/* Try to create a FLOCK lock on filp. We always insert new FLOCK locks + * after any leases, but before any posix locks. + * + * Note that if called with an FL_EXISTS argument, the caller may determine + * whether or not a lock was successfully freed by testing the return + * value for -ENOENT. + */ +static int flock_lock_inode(struct inode *inode, struct file_lock *request) +{ + struct file_lock *new_fl = NULL; + struct file_lock *fl; + struct file_lock_context *ctx; + int error = 0; + bool found = false; + LIST_HEAD(dispose); + + ctx = locks_get_lock_context(inode, request->fl_type); + if (!ctx) { + if (request->fl_type != F_UNLCK) + return -ENOMEM; + return (request->fl_flags & FL_EXISTS) ? -ENOENT : 0; + } + + if (!(request->fl_flags & FL_ACCESS) && (request->fl_type != F_UNLCK)) { + new_fl = locks_alloc_lock(); + if (!new_fl) + return -ENOMEM; + } + + percpu_down_read(&file_rwsem); + spin_lock(&ctx->flc_lock); + if (request->fl_flags & FL_ACCESS) + goto find_conflict; + + list_for_each_entry(fl, &ctx->flc_flock, fl_list) { + if (request->fl_file != fl->fl_file) + continue; + if (request->fl_type == fl->fl_type) + goto out; + found = true; + locks_delete_lock_ctx(fl, &dispose); + break; + } + + if (request->fl_type == F_UNLCK) { + if ((request->fl_flags & FL_EXISTS) && !found) + error = -ENOENT; + goto out; + } + +find_conflict: + list_for_each_entry(fl, &ctx->flc_flock, fl_list) { + if (!flock_locks_conflict(request, fl)) + continue; + error = -EAGAIN; + if (!(request->fl_flags & FL_SLEEP)) + goto out; + error = FILE_LOCK_DEFERRED; + locks_insert_block(fl, request, flock_locks_conflict); + goto out; + } + if (request->fl_flags & FL_ACCESS) + goto out; + locks_copy_lock(new_fl, request); + locks_move_blocks(new_fl, request); + locks_insert_lock_ctx(new_fl, &ctx->flc_flock); + new_fl = NULL; + error = 0; + +out: + spin_unlock(&ctx->flc_lock); + percpu_up_read(&file_rwsem); + if (new_fl) + locks_free_lock(new_fl); + locks_dispose_list(&dispose); + trace_flock_lock_inode(inode, request, error); + return error; +} + +static int posix_lock_inode(struct inode *inode, struct file_lock *request, + struct file_lock *conflock) +{ + struct file_lock *fl, *tmp; + struct file_lock *new_fl = NULL; + struct file_lock *new_fl2 = NULL; + struct file_lock *left = NULL; + struct file_lock *right = NULL; + struct file_lock_context *ctx; + int error; + bool added = false; + LIST_HEAD(dispose); + void *owner; + void (*func)(void); + + ctx = locks_get_lock_context(inode, request->fl_type); + if (!ctx) + return (request->fl_type == F_UNLCK) ? 0 : -ENOMEM; + + /* + * We may need two file_lock structures for this operation, + * so we get them in advance to avoid races. + * + * In some cases we can be sure, that no new locks will be needed + */ + if (!(request->fl_flags & FL_ACCESS) && + (request->fl_type != F_UNLCK || + request->fl_start != 0 || request->fl_end != OFFSET_MAX)) { + new_fl = locks_alloc_lock(); + new_fl2 = locks_alloc_lock(); + } + +retry: + percpu_down_read(&file_rwsem); + spin_lock(&ctx->flc_lock); + /* + * New lock request. Walk all POSIX locks and look for conflicts. If + * there are any, either return error or put the request on the + * blocker's list of waiters and the global blocked_hash. + */ + if (request->fl_type != F_UNLCK) { + list_for_each_entry(fl, &ctx->flc_posix, fl_list) { + if (!posix_locks_conflict(request, fl)) + continue; + if (fl->fl_lmops && fl->fl_lmops->lm_lock_expirable + && (*fl->fl_lmops->lm_lock_expirable)(fl)) { + owner = fl->fl_lmops->lm_mod_owner; + func = fl->fl_lmops->lm_expire_lock; + __module_get(owner); + spin_unlock(&ctx->flc_lock); + percpu_up_read(&file_rwsem); + (*func)(); + module_put(owner); + goto retry; + } + if (conflock) + locks_copy_conflock(conflock, fl); + error = -EAGAIN; + if (!(request->fl_flags & FL_SLEEP)) + goto out; + /* + * Deadlock detection and insertion into the blocked + * locks list must be done while holding the same lock! + */ + error = -EDEADLK; + spin_lock(&blocked_lock_lock); + /* + * Ensure that we don't find any locks blocked on this + * request during deadlock detection. + */ + __locks_wake_up_blocks(request); + if (likely(!posix_locks_deadlock(request, fl))) { + error = FILE_LOCK_DEFERRED; + __locks_insert_block(fl, request, + posix_locks_conflict); + } + spin_unlock(&blocked_lock_lock); + goto out; + } + } + + /* If we're just looking for a conflict, we're done. */ + error = 0; + if (request->fl_flags & FL_ACCESS) + goto out; + + /* Find the first old lock with the same owner as the new lock */ + list_for_each_entry(fl, &ctx->flc_posix, fl_list) { + if (posix_same_owner(request, fl)) + break; + } + + /* Process locks with this owner. */ + list_for_each_entry_safe_from(fl, tmp, &ctx->flc_posix, fl_list) { + if (!posix_same_owner(request, fl)) + break; + + /* Detect adjacent or overlapping regions (if same lock type) */ + if (request->fl_type == fl->fl_type) { + /* In all comparisons of start vs end, use + * "start - 1" rather than "end + 1". If end + * is OFFSET_MAX, end + 1 will become negative. + */ + if (fl->fl_end < request->fl_start - 1) + continue; + /* If the next lock in the list has entirely bigger + * addresses than the new one, insert the lock here. + */ + if (fl->fl_start - 1 > request->fl_end) + break; + + /* If we come here, the new and old lock are of the + * same type and adjacent or overlapping. Make one + * lock yielding from the lower start address of both + * locks to the higher end address. + */ + if (fl->fl_start > request->fl_start) + fl->fl_start = request->fl_start; + else + request->fl_start = fl->fl_start; + if (fl->fl_end < request->fl_end) + fl->fl_end = request->fl_end; + else + request->fl_end = fl->fl_end; + if (added) { + locks_delete_lock_ctx(fl, &dispose); + continue; + } + request = fl; + added = true; + } else { + /* Processing for different lock types is a bit + * more complex. + */ + if (fl->fl_end < request->fl_start) + continue; + if (fl->fl_start > request->fl_end) + break; + if (request->fl_type == F_UNLCK) + added = true; + if (fl->fl_start < request->fl_start) + left = fl; + /* If the next lock in the list has a higher end + * address than the new one, insert the new one here. + */ + if (fl->fl_end > request->fl_end) { + right = fl; + break; + } + if (fl->fl_start >= request->fl_start) { + /* The new lock completely replaces an old + * one (This may happen several times). + */ + if (added) { + locks_delete_lock_ctx(fl, &dispose); + continue; + } + /* + * Replace the old lock with new_fl, and + * remove the old one. It's safe to do the + * insert here since we know that we won't be + * using new_fl later, and that the lock is + * just replacing an existing lock. + */ + error = -ENOLCK; + if (!new_fl) + goto out; + locks_copy_lock(new_fl, request); + locks_move_blocks(new_fl, request); + request = new_fl; + new_fl = NULL; + locks_insert_lock_ctx(request, &fl->fl_list); + locks_delete_lock_ctx(fl, &dispose); + added = true; + } + } + } + + /* + * The above code only modifies existing locks in case of merging or + * replacing. If new lock(s) need to be inserted all modifications are + * done below this, so it's safe yet to bail out. + */ + error = -ENOLCK; /* "no luck" */ + if (right && left == right && !new_fl2) + goto out; + + error = 0; + if (!added) { + if (request->fl_type == F_UNLCK) { + if (request->fl_flags & FL_EXISTS) + error = -ENOENT; + goto out; + } + + if (!new_fl) { + error = -ENOLCK; + goto out; + } + locks_copy_lock(new_fl, request); + locks_move_blocks(new_fl, request); + locks_insert_lock_ctx(new_fl, &fl->fl_list); + fl = new_fl; + new_fl = NULL; + } + if (right) { + if (left == right) { + /* The new lock breaks the old one in two pieces, + * so we have to use the second new lock. + */ + left = new_fl2; + new_fl2 = NULL; + locks_copy_lock(left, right); + locks_insert_lock_ctx(left, &fl->fl_list); + } + right->fl_start = request->fl_end + 1; + locks_wake_up_blocks(right); + } + if (left) { + left->fl_end = request->fl_start - 1; + locks_wake_up_blocks(left); + } + out: + spin_unlock(&ctx->flc_lock); + percpu_up_read(&file_rwsem); + trace_posix_lock_inode(inode, request, error); + /* + * Free any unused locks. + */ + if (new_fl) + locks_free_lock(new_fl); + if (new_fl2) + locks_free_lock(new_fl2); + locks_dispose_list(&dispose); + + return error; +} + +/** + * posix_lock_file - Apply a POSIX-style lock to a file + * @filp: The file to apply the lock to + * @fl: The lock to be applied + * @conflock: Place to return a copy of the conflicting lock, if found. + * + * Add a POSIX style lock to a file. + * We merge adjacent & overlapping locks whenever possible. + * POSIX locks are sorted by owner task, then by starting address + * + * Note that if called with an FL_EXISTS argument, the caller may determine + * whether or not a lock was successfully freed by testing the return + * value for -ENOENT. + */ +int posix_lock_file(struct file *filp, struct file_lock *fl, + struct file_lock *conflock) +{ + return posix_lock_inode(locks_inode(filp), fl, conflock); +} +EXPORT_SYMBOL(posix_lock_file); + +/** + * posix_lock_inode_wait - Apply a POSIX-style lock to a file + * @inode: inode of file to which lock request should be applied + * @fl: The lock to be applied + * + * Apply a POSIX style lock request to an inode. + */ +static int posix_lock_inode_wait(struct inode *inode, struct file_lock *fl) +{ + int error; + might_sleep (); + for (;;) { + error = posix_lock_inode(inode, fl, NULL); + if (error != FILE_LOCK_DEFERRED) + break; + error = wait_event_interruptible(fl->fl_wait, + list_empty(&fl->fl_blocked_member)); + if (error) + break; + } + locks_delete_block(fl); + return error; +} + +static void lease_clear_pending(struct file_lock *fl, int arg) +{ + switch (arg) { + case F_UNLCK: + fl->fl_flags &= ~FL_UNLOCK_PENDING; + fallthrough; + case F_RDLCK: + fl->fl_flags &= ~FL_DOWNGRADE_PENDING; + } +} + +/* We already had a lease on this file; just change its type */ +int lease_modify(struct file_lock *fl, int arg, struct list_head *dispose) +{ + int error = assign_type(fl, arg); + + if (error) + return error; + lease_clear_pending(fl, arg); + locks_wake_up_blocks(fl); + if (arg == F_UNLCK) { + struct file *filp = fl->fl_file; + + f_delown(filp); + filp->f_owner.signum = 0; + fasync_helper(0, fl->fl_file, 0, &fl->fl_fasync); + if (fl->fl_fasync != NULL) { + printk(KERN_ERR "locks_delete_lock: fasync == %p\n", fl->fl_fasync); + fl->fl_fasync = NULL; + } + locks_delete_lock_ctx(fl, dispose); + } + return 0; +} +EXPORT_SYMBOL(lease_modify); + +static bool past_time(unsigned long then) +{ + if (!then) + /* 0 is a special value meaning "this never expires": */ + return false; + return time_after(jiffies, then); +} + +static void time_out_leases(struct inode *inode, struct list_head *dispose) +{ + struct file_lock_context *ctx = inode->i_flctx; + struct file_lock *fl, *tmp; + + lockdep_assert_held(&ctx->flc_lock); + + list_for_each_entry_safe(fl, tmp, &ctx->flc_lease, fl_list) { + trace_time_out_leases(inode, fl); + if (past_time(fl->fl_downgrade_time)) + lease_modify(fl, F_RDLCK, dispose); + if (past_time(fl->fl_break_time)) + lease_modify(fl, F_UNLCK, dispose); + } +} + +static bool leases_conflict(struct file_lock *lease, struct file_lock *breaker) +{ + bool rc; + + if (lease->fl_lmops->lm_breaker_owns_lease + && lease->fl_lmops->lm_breaker_owns_lease(lease)) + return false; + if ((breaker->fl_flags & FL_LAYOUT) != (lease->fl_flags & FL_LAYOUT)) { + rc = false; + goto trace; + } + if ((breaker->fl_flags & FL_DELEG) && (lease->fl_flags & FL_LEASE)) { + rc = false; + goto trace; + } + + rc = locks_conflict(breaker, lease); +trace: + trace_leases_conflict(rc, lease, breaker); + return rc; +} + +static bool +any_leases_conflict(struct inode *inode, struct file_lock *breaker) +{ + struct file_lock_context *ctx = inode->i_flctx; + struct file_lock *fl; + + lockdep_assert_held(&ctx->flc_lock); + + list_for_each_entry(fl, &ctx->flc_lease, fl_list) { + if (leases_conflict(fl, breaker)) + return true; + } + return false; +} + +/** + * __break_lease - revoke all outstanding leases on file + * @inode: the inode of the file to return + * @mode: O_RDONLY: break only write leases; O_WRONLY or O_RDWR: + * break all leases + * @type: FL_LEASE: break leases and delegations; FL_DELEG: break + * only delegations + * + * break_lease (inlined for speed) has checked there already is at least + * some kind of lock (maybe a lease) on this file. Leases are broken on + * a call to open() or truncate(). This function can sleep unless you + * specified %O_NONBLOCK to your open(). + */ +int __break_lease(struct inode *inode, unsigned int mode, unsigned int type) +{ + int error = 0; + struct file_lock_context *ctx; + struct file_lock *new_fl, *fl, *tmp; + unsigned long break_time; + int want_write = (mode & O_ACCMODE) != O_RDONLY; + LIST_HEAD(dispose); + + new_fl = lease_alloc(NULL, want_write ? F_WRLCK : F_RDLCK); + if (IS_ERR(new_fl)) + return PTR_ERR(new_fl); + new_fl->fl_flags = type; + + /* typically we will check that ctx is non-NULL before calling */ + ctx = smp_load_acquire(&inode->i_flctx); + if (!ctx) { + WARN_ON_ONCE(1); + goto free_lock; + } + + percpu_down_read(&file_rwsem); + spin_lock(&ctx->flc_lock); + + time_out_leases(inode, &dispose); + + if (!any_leases_conflict(inode, new_fl)) + goto out; + + break_time = 0; + if (lease_break_time > 0) { + break_time = jiffies + lease_break_time * HZ; + if (break_time == 0) + break_time++; /* so that 0 means no break time */ + } + + list_for_each_entry_safe(fl, tmp, &ctx->flc_lease, fl_list) { + if (!leases_conflict(fl, new_fl)) + continue; + if (want_write) { + if (fl->fl_flags & FL_UNLOCK_PENDING) + continue; + fl->fl_flags |= FL_UNLOCK_PENDING; + fl->fl_break_time = break_time; + } else { + if (lease_breaking(fl)) + continue; + fl->fl_flags |= FL_DOWNGRADE_PENDING; + fl->fl_downgrade_time = break_time; + } + if (fl->fl_lmops->lm_break(fl)) + locks_delete_lock_ctx(fl, &dispose); + } + + if (list_empty(&ctx->flc_lease)) + goto out; + + if (mode & O_NONBLOCK) { + trace_break_lease_noblock(inode, new_fl); + error = -EWOULDBLOCK; + goto out; + } + +restart: + fl = list_first_entry(&ctx->flc_lease, struct file_lock, fl_list); + break_time = fl->fl_break_time; + if (break_time != 0) + break_time -= jiffies; + if (break_time == 0) + break_time++; + locks_insert_block(fl, new_fl, leases_conflict); + trace_break_lease_block(inode, new_fl); + spin_unlock(&ctx->flc_lock); + percpu_up_read(&file_rwsem); + + locks_dispose_list(&dispose); + error = wait_event_interruptible_timeout(new_fl->fl_wait, + list_empty(&new_fl->fl_blocked_member), + break_time); + + percpu_down_read(&file_rwsem); + spin_lock(&ctx->flc_lock); + trace_break_lease_unblock(inode, new_fl); + locks_delete_block(new_fl); + if (error >= 0) { + /* + * Wait for the next conflicting lease that has not been + * broken yet + */ + if (error == 0) + time_out_leases(inode, &dispose); + if (any_leases_conflict(inode, new_fl)) + goto restart; + error = 0; + } +out: + spin_unlock(&ctx->flc_lock); + percpu_up_read(&file_rwsem); + locks_dispose_list(&dispose); +free_lock: + locks_free_lock(new_fl); + return error; +} +EXPORT_SYMBOL(__break_lease); + +/** + * lease_get_mtime - update modified time of an inode with exclusive lease + * @inode: the inode + * @time: pointer to a timespec which contains the last modified time + * + * This is to force NFS clients to flush their caches for files with + * exclusive leases. The justification is that if someone has an + * exclusive lease, then they could be modifying it. + */ +void lease_get_mtime(struct inode *inode, struct timespec64 *time) +{ + bool has_lease = false; + struct file_lock_context *ctx; + struct file_lock *fl; + + ctx = smp_load_acquire(&inode->i_flctx); + if (ctx && !list_empty_careful(&ctx->flc_lease)) { + spin_lock(&ctx->flc_lock); + fl = list_first_entry_or_null(&ctx->flc_lease, + struct file_lock, fl_list); + if (fl && (fl->fl_type == F_WRLCK)) + has_lease = true; + spin_unlock(&ctx->flc_lock); + } + + if (has_lease) + *time = current_time(inode); +} +EXPORT_SYMBOL(lease_get_mtime); + +/** + * fcntl_getlease - Enquire what lease is currently active + * @filp: the file + * + * The value returned by this function will be one of + * (if no lease break is pending): + * + * %F_RDLCK to indicate a shared lease is held. + * + * %F_WRLCK to indicate an exclusive lease is held. + * + * %F_UNLCK to indicate no lease is held. + * + * (if a lease break is pending): + * + * %F_RDLCK to indicate an exclusive lease needs to be + * changed to a shared lease (or removed). + * + * %F_UNLCK to indicate the lease needs to be removed. + * + * XXX: sfr & willy disagree over whether F_INPROGRESS + * should be returned to userspace. + */ +int fcntl_getlease(struct file *filp) +{ + struct file_lock *fl; + struct inode *inode = locks_inode(filp); + struct file_lock_context *ctx; + int type = F_UNLCK; + LIST_HEAD(dispose); + + ctx = smp_load_acquire(&inode->i_flctx); + if (ctx && !list_empty_careful(&ctx->flc_lease)) { + percpu_down_read(&file_rwsem); + spin_lock(&ctx->flc_lock); + time_out_leases(inode, &dispose); + list_for_each_entry(fl, &ctx->flc_lease, fl_list) { + if (fl->fl_file != filp) + continue; + type = target_leasetype(fl); + break; + } + spin_unlock(&ctx->flc_lock); + percpu_up_read(&file_rwsem); + + locks_dispose_list(&dispose); + } + return type; +} + +/** + * check_conflicting_open - see if the given file points to an inode that has + * an existing open that would conflict with the + * desired lease. + * @filp: file to check + * @arg: type of lease that we're trying to acquire + * @flags: current lock flags + * + * Check to see if there's an existing open fd on this file that would + * conflict with the lease we're trying to set. + */ +static int +check_conflicting_open(struct file *filp, const long arg, int flags) +{ + struct inode *inode = locks_inode(filp); + int self_wcount = 0, self_rcount = 0; + + if (flags & FL_LAYOUT) + return 0; + if (flags & FL_DELEG) + /* We leave these checks to the caller */ + return 0; + + if (arg == F_RDLCK) + return inode_is_open_for_write(inode) ? -EAGAIN : 0; + else if (arg != F_WRLCK) + return 0; + + /* + * Make sure that only read/write count is from lease requestor. + * Note that this will result in denying write leases when i_writecount + * is negative, which is what we want. (We shouldn't grant write leases + * on files open for execution.) + */ + if (filp->f_mode & FMODE_WRITE) + self_wcount = 1; + else if (filp->f_mode & FMODE_READ) + self_rcount = 1; + + if (atomic_read(&inode->i_writecount) != self_wcount || + atomic_read(&inode->i_readcount) != self_rcount) + return -EAGAIN; + + return 0; +} + +static int +generic_add_lease(struct file *filp, long arg, struct file_lock **flp, void **priv) +{ + struct file_lock *fl, *my_fl = NULL, *lease; + struct inode *inode = locks_inode(filp); + struct file_lock_context *ctx; + bool is_deleg = (*flp)->fl_flags & FL_DELEG; + int error; + LIST_HEAD(dispose); + + lease = *flp; + trace_generic_add_lease(inode, lease); + + /* Note that arg is never F_UNLCK here */ + ctx = locks_get_lock_context(inode, arg); + if (!ctx) + return -ENOMEM; + + /* + * In the delegation case we need mutual exclusion with + * a number of operations that take the i_mutex. We trylock + * because delegations are an optional optimization, and if + * there's some chance of a conflict--we'd rather not + * bother, maybe that's a sign this just isn't a good file to + * hand out a delegation on. + */ + if (is_deleg && !inode_trylock(inode)) + return -EAGAIN; + + if (is_deleg && arg == F_WRLCK) { + /* Write delegations are not currently supported: */ + inode_unlock(inode); + WARN_ON_ONCE(1); + return -EINVAL; + } + + percpu_down_read(&file_rwsem); + spin_lock(&ctx->flc_lock); + time_out_leases(inode, &dispose); + error = check_conflicting_open(filp, arg, lease->fl_flags); + if (error) + goto out; + + /* + * At this point, we know that if there is an exclusive + * lease on this file, then we hold it on this filp + * (otherwise our open of this file would have blocked). + * And if we are trying to acquire an exclusive lease, + * then the file is not open by anyone (including us) + * except for this filp. + */ + error = -EAGAIN; + list_for_each_entry(fl, &ctx->flc_lease, fl_list) { + if (fl->fl_file == filp && + fl->fl_owner == lease->fl_owner) { + my_fl = fl; + continue; + } + + /* + * No exclusive leases if someone else has a lease on + * this file: + */ + if (arg == F_WRLCK) + goto out; + /* + * Modifying our existing lease is OK, but no getting a + * new lease if someone else is opening for write: + */ + if (fl->fl_flags & FL_UNLOCK_PENDING) + goto out; + } + + if (my_fl != NULL) { + lease = my_fl; + error = lease->fl_lmops->lm_change(lease, arg, &dispose); + if (error) + goto out; + goto out_setup; + } + + error = -EINVAL; + if (!leases_enable) + goto out; + + locks_insert_lock_ctx(lease, &ctx->flc_lease); + /* + * The check in break_lease() is lockless. It's possible for another + * open to race in after we did the earlier check for a conflicting + * open but before the lease was inserted. Check again for a + * conflicting open and cancel the lease if there is one. + * + * We also add a barrier here to ensure that the insertion of the lock + * precedes these checks. + */ + smp_mb(); + error = check_conflicting_open(filp, arg, lease->fl_flags); + if (error) { + locks_unlink_lock_ctx(lease); + goto out; + } + +out_setup: + if (lease->fl_lmops->lm_setup) + lease->fl_lmops->lm_setup(lease, priv); +out: + spin_unlock(&ctx->flc_lock); + percpu_up_read(&file_rwsem); + locks_dispose_list(&dispose); + if (is_deleg) + inode_unlock(inode); + if (!error && !my_fl) + *flp = NULL; + return error; +} + +static int generic_delete_lease(struct file *filp, void *owner) +{ + int error = -EAGAIN; + struct file_lock *fl, *victim = NULL; + struct inode *inode = locks_inode(filp); + struct file_lock_context *ctx; + LIST_HEAD(dispose); + + ctx = smp_load_acquire(&inode->i_flctx); + if (!ctx) { + trace_generic_delete_lease(inode, NULL); + return error; + } + + percpu_down_read(&file_rwsem); + spin_lock(&ctx->flc_lock); + list_for_each_entry(fl, &ctx->flc_lease, fl_list) { + if (fl->fl_file == filp && + fl->fl_owner == owner) { + victim = fl; + break; + } + } + trace_generic_delete_lease(inode, victim); + if (victim) + error = fl->fl_lmops->lm_change(victim, F_UNLCK, &dispose); + spin_unlock(&ctx->flc_lock); + percpu_up_read(&file_rwsem); + locks_dispose_list(&dispose); + return error; +} + +/** + * generic_setlease - sets a lease on an open file + * @filp: file pointer + * @arg: type of lease to obtain + * @flp: input - file_lock to use, output - file_lock inserted + * @priv: private data for lm_setup (may be NULL if lm_setup + * doesn't require it) + * + * The (input) flp->fl_lmops->lm_break function is required + * by break_lease(). + */ +int generic_setlease(struct file *filp, long arg, struct file_lock **flp, + void **priv) +{ + struct inode *inode = locks_inode(filp); + vfsuid_t vfsuid = i_uid_into_vfsuid(file_mnt_user_ns(filp), inode); + int error; + + if ((!vfsuid_eq_kuid(vfsuid, current_fsuid())) && !capable(CAP_LEASE)) + return -EACCES; + if (!S_ISREG(inode->i_mode)) + return -EINVAL; + error = security_file_lock(filp, arg); + if (error) + return error; + + switch (arg) { + case F_UNLCK: + return generic_delete_lease(filp, *priv); + case F_RDLCK: + case F_WRLCK: + if (!(*flp)->fl_lmops->lm_break) { + WARN_ON_ONCE(1); + return -ENOLCK; + } + + return generic_add_lease(filp, arg, flp, priv); + default: + return -EINVAL; + } +} +EXPORT_SYMBOL(generic_setlease); + +#if IS_ENABLED(CONFIG_SRCU) +/* + * Kernel subsystems can register to be notified on any attempt to set + * a new lease with the lease_notifier_chain. This is used by (e.g.) nfsd + * to close files that it may have cached when there is an attempt to set a + * conflicting lease. + */ +static struct srcu_notifier_head lease_notifier_chain; + +static inline void +lease_notifier_chain_init(void) +{ + srcu_init_notifier_head(&lease_notifier_chain); +} + +static inline void +setlease_notifier(long arg, struct file_lock *lease) +{ + if (arg != F_UNLCK) + srcu_notifier_call_chain(&lease_notifier_chain, arg, lease); +} + +int lease_register_notifier(struct notifier_block *nb) +{ + return srcu_notifier_chain_register(&lease_notifier_chain, nb); +} +EXPORT_SYMBOL_GPL(lease_register_notifier); + +void lease_unregister_notifier(struct notifier_block *nb) +{ + srcu_notifier_chain_unregister(&lease_notifier_chain, nb); +} +EXPORT_SYMBOL_GPL(lease_unregister_notifier); + +#else /* !IS_ENABLED(CONFIG_SRCU) */ +static inline void +lease_notifier_chain_init(void) +{ +} + +static inline void +setlease_notifier(long arg, struct file_lock *lease) +{ +} + +int lease_register_notifier(struct notifier_block *nb) +{ + return 0; +} +EXPORT_SYMBOL_GPL(lease_register_notifier); + +void lease_unregister_notifier(struct notifier_block *nb) +{ +} +EXPORT_SYMBOL_GPL(lease_unregister_notifier); + +#endif /* IS_ENABLED(CONFIG_SRCU) */ + +/** + * vfs_setlease - sets a lease on an open file + * @filp: file pointer + * @arg: type of lease to obtain + * @lease: file_lock to use when adding a lease + * @priv: private info for lm_setup when adding a lease (may be + * NULL if lm_setup doesn't require it) + * + * Call this to establish a lease on the file. The "lease" argument is not + * used for F_UNLCK requests and may be NULL. For commands that set or alter + * an existing lease, the ``(*lease)->fl_lmops->lm_break`` operation must be + * set; if not, this function will return -ENOLCK (and generate a scary-looking + * stack trace). + * + * The "priv" pointer is passed directly to the lm_setup function as-is. It + * may be NULL if the lm_setup operation doesn't require it. + */ +int +vfs_setlease(struct file *filp, long arg, struct file_lock **lease, void **priv) +{ + if (lease) + setlease_notifier(arg, *lease); + if (filp->f_op->setlease) + return filp->f_op->setlease(filp, arg, lease, priv); + else + return generic_setlease(filp, arg, lease, priv); +} +EXPORT_SYMBOL_GPL(vfs_setlease); + +static int do_fcntl_add_lease(unsigned int fd, struct file *filp, long arg) +{ + struct file_lock *fl; + struct fasync_struct *new; + int error; + + fl = lease_alloc(filp, arg); + if (IS_ERR(fl)) + return PTR_ERR(fl); + + new = fasync_alloc(); + if (!new) { + locks_free_lock(fl); + return -ENOMEM; + } + new->fa_fd = fd; + + error = vfs_setlease(filp, arg, &fl, (void **)&new); + if (fl) + locks_free_lock(fl); + if (new) + fasync_free(new); + return error; +} + +/** + * fcntl_setlease - sets a lease on an open file + * @fd: open file descriptor + * @filp: file pointer + * @arg: type of lease to obtain + * + * Call this fcntl to establish a lease on the file. + * Note that you also need to call %F_SETSIG to + * receive a signal when the lease is broken. + */ +int fcntl_setlease(unsigned int fd, struct file *filp, long arg) +{ + if (arg == F_UNLCK) + return vfs_setlease(filp, F_UNLCK, NULL, (void **)&filp); + return do_fcntl_add_lease(fd, filp, arg); +} + +/** + * flock_lock_inode_wait - Apply a FLOCK-style lock to a file + * @inode: inode of the file to apply to + * @fl: The lock to be applied + * + * Apply a FLOCK style lock request to an inode. + */ +static int flock_lock_inode_wait(struct inode *inode, struct file_lock *fl) +{ + int error; + might_sleep(); + for (;;) { + error = flock_lock_inode(inode, fl); + if (error != FILE_LOCK_DEFERRED) + break; + error = wait_event_interruptible(fl->fl_wait, + list_empty(&fl->fl_blocked_member)); + if (error) + break; + } + locks_delete_block(fl); + return error; +} + +/** + * locks_lock_inode_wait - Apply a lock to an inode + * @inode: inode of the file to apply to + * @fl: The lock to be applied + * + * Apply a POSIX or FLOCK style lock request to an inode. + */ +int locks_lock_inode_wait(struct inode *inode, struct file_lock *fl) +{ + int res = 0; + switch (fl->fl_flags & (FL_POSIX|FL_FLOCK)) { + case FL_POSIX: + res = posix_lock_inode_wait(inode, fl); + break; + case FL_FLOCK: + res = flock_lock_inode_wait(inode, fl); + break; + default: + BUG(); + } + return res; +} +EXPORT_SYMBOL(locks_lock_inode_wait); + +/** + * sys_flock: - flock() system call. + * @fd: the file descriptor to lock. + * @cmd: the type of lock to apply. + * + * Apply a %FL_FLOCK style lock to an open file descriptor. + * The @cmd can be one of: + * + * - %LOCK_SH -- a shared lock. + * - %LOCK_EX -- an exclusive lock. + * - %LOCK_UN -- remove an existing lock. + * - %LOCK_MAND -- a 'mandatory' flock. (DEPRECATED) + * + * %LOCK_MAND support has been removed from the kernel. + */ +SYSCALL_DEFINE2(flock, unsigned int, fd, unsigned int, cmd) +{ + int can_sleep, error, type; + struct file_lock fl; + struct fd f; + + /* + * LOCK_MAND locks were broken for a long time in that they never + * conflicted with one another and didn't prevent any sort of open, + * read or write activity. + * + * Just ignore these requests now, to preserve legacy behavior, but + * throw a warning to let people know that they don't actually work. + */ + if (cmd & LOCK_MAND) { + pr_warn_once("Attempt to set a LOCK_MAND lock via flock(2). This support has been removed and the request ignored.\n"); + return 0; + } + + type = flock_translate_cmd(cmd & ~LOCK_NB); + if (type < 0) + return type; + + error = -EBADF; + f = fdget(fd); + if (!f.file) + return error; + + if (type != F_UNLCK && !(f.file->f_mode & (FMODE_READ | FMODE_WRITE))) + goto out_putf; + + flock_make_lock(f.file, &fl, type); + + error = security_file_lock(f.file, fl.fl_type); + if (error) + goto out_putf; + + can_sleep = !(cmd & LOCK_NB); + if (can_sleep) + fl.fl_flags |= FL_SLEEP; + + if (f.file->f_op->flock) + error = f.file->f_op->flock(f.file, + (can_sleep) ? F_SETLKW : F_SETLK, + &fl); + else + error = locks_lock_file_wait(f.file, &fl); + + locks_release_private(&fl); + out_putf: + fdput(f); + + return error; +} + +/** + * vfs_test_lock - test file byte range lock + * @filp: The file to test lock for + * @fl: The lock to test; also used to hold result + * + * Returns -ERRNO on failure. Indicates presence of conflicting lock by + * setting conf->fl_type to something other than F_UNLCK. + */ +int vfs_test_lock(struct file *filp, struct file_lock *fl) +{ + if (filp->f_op->lock) + return filp->f_op->lock(filp, F_GETLK, fl); + posix_test_lock(filp, fl); + return 0; +} +EXPORT_SYMBOL_GPL(vfs_test_lock); + +/** + * locks_translate_pid - translate a file_lock's fl_pid number into a namespace + * @fl: The file_lock who's fl_pid should be translated + * @ns: The namespace into which the pid should be translated + * + * Used to tranlate a fl_pid into a namespace virtual pid number + */ +static pid_t locks_translate_pid(struct file_lock *fl, struct pid_namespace *ns) +{ + pid_t vnr; + struct pid *pid; + + if (IS_OFDLCK(fl)) + return -1; + if (IS_REMOTELCK(fl)) + return fl->fl_pid; + /* + * If the flock owner process is dead and its pid has been already + * freed, the translation below won't work, but we still want to show + * flock owner pid number in init pidns. + */ + if (ns == &init_pid_ns) + return (pid_t)fl->fl_pid; + + rcu_read_lock(); + pid = find_pid_ns(fl->fl_pid, &init_pid_ns); + vnr = pid_nr_ns(pid, ns); + rcu_read_unlock(); + return vnr; +} + +static int posix_lock_to_flock(struct flock *flock, struct file_lock *fl) +{ + flock->l_pid = locks_translate_pid(fl, task_active_pid_ns(current)); +#if BITS_PER_LONG == 32 + /* + * Make sure we can represent the posix lock via + * legacy 32bit flock. + */ + if (fl->fl_start > OFFT_OFFSET_MAX) + return -EOVERFLOW; + if (fl->fl_end != OFFSET_MAX && fl->fl_end > OFFT_OFFSET_MAX) + return -EOVERFLOW; +#endif + flock->l_start = fl->fl_start; + flock->l_len = fl->fl_end == OFFSET_MAX ? 0 : + fl->fl_end - fl->fl_start + 1; + flock->l_whence = 0; + flock->l_type = fl->fl_type; + return 0; +} + +#if BITS_PER_LONG == 32 +static void posix_lock_to_flock64(struct flock64 *flock, struct file_lock *fl) +{ + flock->l_pid = locks_translate_pid(fl, task_active_pid_ns(current)); + flock->l_start = fl->fl_start; + flock->l_len = fl->fl_end == OFFSET_MAX ? 0 : + fl->fl_end - fl->fl_start + 1; + flock->l_whence = 0; + flock->l_type = fl->fl_type; +} +#endif + +/* Report the first existing lock that would conflict with l. + * This implements the F_GETLK command of fcntl(). + */ +int fcntl_getlk(struct file *filp, unsigned int cmd, struct flock *flock) +{ + struct file_lock *fl; + int error; + + fl = locks_alloc_lock(); + if (fl == NULL) + return -ENOMEM; + error = -EINVAL; + if (flock->l_type != F_RDLCK && flock->l_type != F_WRLCK) + goto out; + + error = flock_to_posix_lock(filp, fl, flock); + if (error) + goto out; + + if (cmd == F_OFD_GETLK) { + error = -EINVAL; + if (flock->l_pid != 0) + goto out; + + fl->fl_flags |= FL_OFDLCK; + fl->fl_owner = filp; + } + + error = vfs_test_lock(filp, fl); + if (error) + goto out; + + flock->l_type = fl->fl_type; + if (fl->fl_type != F_UNLCK) { + error = posix_lock_to_flock(flock, fl); + if (error) + goto out; + } +out: + locks_free_lock(fl); + return error; +} + +/** + * vfs_lock_file - file byte range lock + * @filp: The file to apply the lock to + * @cmd: type of locking operation (F_SETLK, F_GETLK, etc.) + * @fl: The lock to be applied + * @conf: Place to return a copy of the conflicting lock, if found. + * + * A caller that doesn't care about the conflicting lock may pass NULL + * as the final argument. + * + * If the filesystem defines a private ->lock() method, then @conf will + * be left unchanged; so a caller that cares should initialize it to + * some acceptable default. + * + * To avoid blocking kernel daemons, such as lockd, that need to acquire POSIX + * locks, the ->lock() interface may return asynchronously, before the lock has + * been granted or denied by the underlying filesystem, if (and only if) + * lm_grant is set. Callers expecting ->lock() to return asynchronously + * will only use F_SETLK, not F_SETLKW; they will set FL_SLEEP if (and only if) + * the request is for a blocking lock. When ->lock() does return asynchronously, + * it must return FILE_LOCK_DEFERRED, and call ->lm_grant() when the lock + * request completes. + * If the request is for non-blocking lock the file system should return + * FILE_LOCK_DEFERRED then try to get the lock and call the callback routine + * with the result. If the request timed out the callback routine will return a + * nonzero return code and the file system should release the lock. The file + * system is also responsible to keep a corresponding posix lock when it + * grants a lock so the VFS can find out which locks are locally held and do + * the correct lock cleanup when required. + * The underlying filesystem must not drop the kernel lock or call + * ->lm_grant() before returning to the caller with a FILE_LOCK_DEFERRED + * return code. + */ +int vfs_lock_file(struct file *filp, unsigned int cmd, struct file_lock *fl, struct file_lock *conf) +{ + if (filp->f_op->lock) + return filp->f_op->lock(filp, cmd, fl); + else + return posix_lock_file(filp, fl, conf); +} +EXPORT_SYMBOL_GPL(vfs_lock_file); + +static int do_lock_file_wait(struct file *filp, unsigned int cmd, + struct file_lock *fl) +{ + int error; + + error = security_file_lock(filp, fl->fl_type); + if (error) + return error; + + for (;;) { + error = vfs_lock_file(filp, cmd, fl, NULL); + if (error != FILE_LOCK_DEFERRED) + break; + error = wait_event_interruptible(fl->fl_wait, + list_empty(&fl->fl_blocked_member)); + if (error) + break; + } + locks_delete_block(fl); + + return error; +} + +/* Ensure that fl->fl_file has compatible f_mode for F_SETLK calls */ +static int +check_fmode_for_setlk(struct file_lock *fl) +{ + switch (fl->fl_type) { + case F_RDLCK: + if (!(fl->fl_file->f_mode & FMODE_READ)) + return -EBADF; + break; + case F_WRLCK: + if (!(fl->fl_file->f_mode & FMODE_WRITE)) + return -EBADF; + } + return 0; +} + +/* Apply the lock described by l to an open file descriptor. + * This implements both the F_SETLK and F_SETLKW commands of fcntl(). + */ +int fcntl_setlk(unsigned int fd, struct file *filp, unsigned int cmd, + struct flock *flock) +{ + struct file_lock *file_lock = locks_alloc_lock(); + struct inode *inode = locks_inode(filp); + struct file *f; + int error; + + if (file_lock == NULL) + return -ENOLCK; + + error = flock_to_posix_lock(filp, file_lock, flock); + if (error) + goto out; + + error = check_fmode_for_setlk(file_lock); + if (error) + goto out; + + /* + * If the cmd is requesting file-private locks, then set the + * FL_OFDLCK flag and override the owner. + */ + switch (cmd) { + case F_OFD_SETLK: + error = -EINVAL; + if (flock->l_pid != 0) + goto out; + + cmd = F_SETLK; + file_lock->fl_flags |= FL_OFDLCK; + file_lock->fl_owner = filp; + break; + case F_OFD_SETLKW: + error = -EINVAL; + if (flock->l_pid != 0) + goto out; + + cmd = F_SETLKW; + file_lock->fl_flags |= FL_OFDLCK; + file_lock->fl_owner = filp; + fallthrough; + case F_SETLKW: + file_lock->fl_flags |= FL_SLEEP; + } + + error = do_lock_file_wait(filp, cmd, file_lock); + + /* + * Attempt to detect a close/fcntl race and recover by releasing the + * lock that was just acquired. There is no need to do that when we're + * unlocking though, or for OFD locks. + */ + if (!error && file_lock->fl_type != F_UNLCK && + !(file_lock->fl_flags & FL_OFDLCK)) { + struct files_struct *files = current->files; + /* + * We need that spin_lock here - it prevents reordering between + * update of i_flctx->flc_posix and check for it done in + * close(). rcu_read_lock() wouldn't do. + */ + spin_lock(&files->file_lock); + f = files_lookup_fd_locked(files, fd); + spin_unlock(&files->file_lock); + if (f != filp) { + file_lock->fl_type = F_UNLCK; + error = do_lock_file_wait(filp, cmd, file_lock); + WARN_ON_ONCE(error); + error = -EBADF; + } + } +out: + trace_fcntl_setlk(inode, file_lock, error); + locks_free_lock(file_lock); + return error; +} + +#if BITS_PER_LONG == 32 +/* Report the first existing lock that would conflict with l. + * This implements the F_GETLK command of fcntl(). + */ +int fcntl_getlk64(struct file *filp, unsigned int cmd, struct flock64 *flock) +{ + struct file_lock *fl; + int error; + + fl = locks_alloc_lock(); + if (fl == NULL) + return -ENOMEM; + + error = -EINVAL; + if (flock->l_type != F_RDLCK && flock->l_type != F_WRLCK) + goto out; + + error = flock64_to_posix_lock(filp, fl, flock); + if (error) + goto out; + + if (cmd == F_OFD_GETLK) { + error = -EINVAL; + if (flock->l_pid != 0) + goto out; + + cmd = F_GETLK64; + fl->fl_flags |= FL_OFDLCK; + fl->fl_owner = filp; + } + + error = vfs_test_lock(filp, fl); + if (error) + goto out; + + flock->l_type = fl->fl_type; + if (fl->fl_type != F_UNLCK) + posix_lock_to_flock64(flock, fl); + +out: + locks_free_lock(fl); + return error; +} + +/* Apply the lock described by l to an open file descriptor. + * This implements both the F_SETLK and F_SETLKW commands of fcntl(). + */ +int fcntl_setlk64(unsigned int fd, struct file *filp, unsigned int cmd, + struct flock64 *flock) +{ + struct file_lock *file_lock = locks_alloc_lock(); + struct file *f; + int error; + + if (file_lock == NULL) + return -ENOLCK; + + error = flock64_to_posix_lock(filp, file_lock, flock); + if (error) + goto out; + + error = check_fmode_for_setlk(file_lock); + if (error) + goto out; + + /* + * If the cmd is requesting file-private locks, then set the + * FL_OFDLCK flag and override the owner. + */ + switch (cmd) { + case F_OFD_SETLK: + error = -EINVAL; + if (flock->l_pid != 0) + goto out; + + cmd = F_SETLK64; + file_lock->fl_flags |= FL_OFDLCK; + file_lock->fl_owner = filp; + break; + case F_OFD_SETLKW: + error = -EINVAL; + if (flock->l_pid != 0) + goto out; + + cmd = F_SETLKW64; + file_lock->fl_flags |= FL_OFDLCK; + file_lock->fl_owner = filp; + fallthrough; + case F_SETLKW64: + file_lock->fl_flags |= FL_SLEEP; + } + + error = do_lock_file_wait(filp, cmd, file_lock); + + /* + * Attempt to detect a close/fcntl race and recover by releasing the + * lock that was just acquired. There is no need to do that when we're + * unlocking though, or for OFD locks. + */ + if (!error && file_lock->fl_type != F_UNLCK && + !(file_lock->fl_flags & FL_OFDLCK)) { + struct files_struct *files = current->files; + /* + * We need that spin_lock here - it prevents reordering between + * update of i_flctx->flc_posix and check for it done in + * close(). rcu_read_lock() wouldn't do. + */ + spin_lock(&files->file_lock); + f = files_lookup_fd_locked(files, fd); + spin_unlock(&files->file_lock); + if (f != filp) { + file_lock->fl_type = F_UNLCK; + error = do_lock_file_wait(filp, cmd, file_lock); + WARN_ON_ONCE(error); + error = -EBADF; + } + } +out: + locks_free_lock(file_lock); + return error; +} +#endif /* BITS_PER_LONG == 32 */ + +/* + * This function is called when the file is being removed + * from the task's fd array. POSIX locks belonging to this task + * are deleted at this time. + */ +void locks_remove_posix(struct file *filp, fl_owner_t owner) +{ + int error; + struct inode *inode = locks_inode(filp); + struct file_lock lock; + struct file_lock_context *ctx; + + /* + * If there are no locks held on this file, we don't need to call + * posix_lock_file(). Another process could be setting a lock on this + * file at the same time, but we wouldn't remove that lock anyway. + */ + ctx = smp_load_acquire(&inode->i_flctx); + if (!ctx || list_empty(&ctx->flc_posix)) + return; + + locks_init_lock(&lock); + lock.fl_type = F_UNLCK; + lock.fl_flags = FL_POSIX | FL_CLOSE; + lock.fl_start = 0; + lock.fl_end = OFFSET_MAX; + lock.fl_owner = owner; + lock.fl_pid = current->tgid; + lock.fl_file = filp; + lock.fl_ops = NULL; + lock.fl_lmops = NULL; + + error = vfs_lock_file(filp, F_SETLK, &lock, NULL); + + if (lock.fl_ops && lock.fl_ops->fl_release_private) + lock.fl_ops->fl_release_private(&lock); + trace_locks_remove_posix(inode, &lock, error); +} +EXPORT_SYMBOL(locks_remove_posix); + +/* The i_flctx must be valid when calling into here */ +static void +locks_remove_flock(struct file *filp, struct file_lock_context *flctx) +{ + struct file_lock fl; + struct inode *inode = locks_inode(filp); + + if (list_empty(&flctx->flc_flock)) + return; + + flock_make_lock(filp, &fl, F_UNLCK); + fl.fl_flags |= FL_CLOSE; + + if (filp->f_op->flock) + filp->f_op->flock(filp, F_SETLKW, &fl); + else + flock_lock_inode(inode, &fl); + + if (fl.fl_ops && fl.fl_ops->fl_release_private) + fl.fl_ops->fl_release_private(&fl); +} + +/* The i_flctx must be valid when calling into here */ +static void +locks_remove_lease(struct file *filp, struct file_lock_context *ctx) +{ + struct file_lock *fl, *tmp; + LIST_HEAD(dispose); + + if (list_empty(&ctx->flc_lease)) + return; + + percpu_down_read(&file_rwsem); + spin_lock(&ctx->flc_lock); + list_for_each_entry_safe(fl, tmp, &ctx->flc_lease, fl_list) + if (filp == fl->fl_file) + lease_modify(fl, F_UNLCK, &dispose); + spin_unlock(&ctx->flc_lock); + percpu_up_read(&file_rwsem); + + locks_dispose_list(&dispose); +} + +/* + * This function is called on the last close of an open file. + */ +void locks_remove_file(struct file *filp) +{ + struct file_lock_context *ctx; + + ctx = smp_load_acquire(&locks_inode(filp)->i_flctx); + if (!ctx) + return; + + /* remove any OFD locks */ + locks_remove_posix(filp, filp); + + /* remove flock locks */ + locks_remove_flock(filp, ctx); + + /* remove any leases */ + locks_remove_lease(filp, ctx); + + spin_lock(&ctx->flc_lock); + locks_check_ctx_file_list(filp, &ctx->flc_posix, "POSIX"); + locks_check_ctx_file_list(filp, &ctx->flc_flock, "FLOCK"); + locks_check_ctx_file_list(filp, &ctx->flc_lease, "LEASE"); + spin_unlock(&ctx->flc_lock); +} + +/** + * vfs_cancel_lock - file byte range unblock lock + * @filp: The file to apply the unblock to + * @fl: The lock to be unblocked + * + * Used by lock managers to cancel blocked requests + */ +int vfs_cancel_lock(struct file *filp, struct file_lock *fl) +{ + if (filp->f_op->lock) + return filp->f_op->lock(filp, F_CANCELLK, fl); + return 0; +} +EXPORT_SYMBOL_GPL(vfs_cancel_lock); + +/** + * vfs_inode_has_locks - are any file locks held on @inode? + * @inode: inode to check for locks + * + * Return true if there are any FL_POSIX or FL_FLOCK locks currently + * set on @inode. + */ +bool vfs_inode_has_locks(struct inode *inode) +{ + struct file_lock_context *ctx; + bool ret; + + ctx = smp_load_acquire(&inode->i_flctx); + if (!ctx) + return false; + + spin_lock(&ctx->flc_lock); + ret = !list_empty(&ctx->flc_posix) || !list_empty(&ctx->flc_flock); + spin_unlock(&ctx->flc_lock); + return ret; +} +EXPORT_SYMBOL_GPL(vfs_inode_has_locks); + +#ifdef CONFIG_PROC_FS +#include <linux/proc_fs.h> +#include <linux/seq_file.h> + +struct locks_iterator { + int li_cpu; + loff_t li_pos; +}; + +static void lock_get_status(struct seq_file *f, struct file_lock *fl, + loff_t id, char *pfx, int repeat) +{ + struct inode *inode = NULL; + unsigned int fl_pid; + struct pid_namespace *proc_pidns = proc_pid_ns(file_inode(f->file)->i_sb); + int type; + + fl_pid = locks_translate_pid(fl, proc_pidns); + /* + * If lock owner is dead (and pid is freed) or not visible in current + * pidns, zero is shown as a pid value. Check lock info from + * init_pid_ns to get saved lock pid value. + */ + + if (fl->fl_file != NULL) + inode = locks_inode(fl->fl_file); + + seq_printf(f, "%lld: ", id); + + if (repeat) + seq_printf(f, "%*s", repeat - 1 + (int)strlen(pfx), pfx); + + if (IS_POSIX(fl)) { + if (fl->fl_flags & FL_ACCESS) + seq_puts(f, "ACCESS"); + else if (IS_OFDLCK(fl)) + seq_puts(f, "OFDLCK"); + else + seq_puts(f, "POSIX "); + + seq_printf(f, " %s ", + (inode == NULL) ? "*NOINODE*" : "ADVISORY "); + } else if (IS_FLOCK(fl)) { + seq_puts(f, "FLOCK ADVISORY "); + } else if (IS_LEASE(fl)) { + if (fl->fl_flags & FL_DELEG) + seq_puts(f, "DELEG "); + else + seq_puts(f, "LEASE "); + + if (lease_breaking(fl)) + seq_puts(f, "BREAKING "); + else if (fl->fl_file) + seq_puts(f, "ACTIVE "); + else + seq_puts(f, "BREAKER "); + } else { + seq_puts(f, "UNKNOWN UNKNOWN "); + } + type = IS_LEASE(fl) ? target_leasetype(fl) : fl->fl_type; + + seq_printf(f, "%s ", (type == F_WRLCK) ? "WRITE" : + (type == F_RDLCK) ? "READ" : "UNLCK"); + if (inode) { + /* userspace relies on this representation of dev_t */ + seq_printf(f, "%d %02x:%02x:%lu ", fl_pid, + MAJOR(inode->i_sb->s_dev), + MINOR(inode->i_sb->s_dev), inode->i_ino); + } else { + seq_printf(f, "%d <none>:0 ", fl_pid); + } + if (IS_POSIX(fl)) { + if (fl->fl_end == OFFSET_MAX) + seq_printf(f, "%Ld EOF\n", fl->fl_start); + else + seq_printf(f, "%Ld %Ld\n", fl->fl_start, fl->fl_end); + } else { + seq_puts(f, "0 EOF\n"); + } +} + +static struct file_lock *get_next_blocked_member(struct file_lock *node) +{ + struct file_lock *tmp; + + /* NULL node or root node */ + if (node == NULL || node->fl_blocker == NULL) + return NULL; + + /* Next member in the linked list could be itself */ + tmp = list_next_entry(node, fl_blocked_member); + if (list_entry_is_head(tmp, &node->fl_blocker->fl_blocked_requests, fl_blocked_member) + || tmp == node) { + return NULL; + } + + return tmp; +} + +static int locks_show(struct seq_file *f, void *v) +{ + struct locks_iterator *iter = f->private; + struct file_lock *cur, *tmp; + struct pid_namespace *proc_pidns = proc_pid_ns(file_inode(f->file)->i_sb); + int level = 0; + + cur = hlist_entry(v, struct file_lock, fl_link); + + if (locks_translate_pid(cur, proc_pidns) == 0) + return 0; + + /* View this crossed linked list as a binary tree, the first member of fl_blocked_requests + * is the left child of current node, the next silibing in fl_blocked_member is the + * right child, we can alse get the parent of current node from fl_blocker, so this + * question becomes traversal of a binary tree + */ + while (cur != NULL) { + if (level) + lock_get_status(f, cur, iter->li_pos, "-> ", level); + else + lock_get_status(f, cur, iter->li_pos, "", level); + + if (!list_empty(&cur->fl_blocked_requests)) { + /* Turn left */ + cur = list_first_entry_or_null(&cur->fl_blocked_requests, + struct file_lock, fl_blocked_member); + level++; + } else { + /* Turn right */ + tmp = get_next_blocked_member(cur); + /* Fall back to parent node */ + while (tmp == NULL && cur->fl_blocker != NULL) { + cur = cur->fl_blocker; + level--; + tmp = get_next_blocked_member(cur); + } + cur = tmp; + } + } + + return 0; +} + +static void __show_fd_locks(struct seq_file *f, + struct list_head *head, int *id, + struct file *filp, struct files_struct *files) +{ + struct file_lock *fl; + + list_for_each_entry(fl, head, fl_list) { + + if (filp != fl->fl_file) + continue; + if (fl->fl_owner != files && + fl->fl_owner != filp) + continue; + + (*id)++; + seq_puts(f, "lock:\t"); + lock_get_status(f, fl, *id, "", 0); + } +} + +void show_fd_locks(struct seq_file *f, + struct file *filp, struct files_struct *files) +{ + struct inode *inode = locks_inode(filp); + struct file_lock_context *ctx; + int id = 0; + + ctx = smp_load_acquire(&inode->i_flctx); + if (!ctx) + return; + + spin_lock(&ctx->flc_lock); + __show_fd_locks(f, &ctx->flc_flock, &id, filp, files); + __show_fd_locks(f, &ctx->flc_posix, &id, filp, files); + __show_fd_locks(f, &ctx->flc_lease, &id, filp, files); + spin_unlock(&ctx->flc_lock); +} + +static void *locks_start(struct seq_file *f, loff_t *pos) + __acquires(&blocked_lock_lock) +{ + struct locks_iterator *iter = f->private; + + iter->li_pos = *pos + 1; + percpu_down_write(&file_rwsem); + spin_lock(&blocked_lock_lock); + return seq_hlist_start_percpu(&file_lock_list.hlist, &iter->li_cpu, *pos); +} + +static void *locks_next(struct seq_file *f, void *v, loff_t *pos) +{ + struct locks_iterator *iter = f->private; + + ++iter->li_pos; + return seq_hlist_next_percpu(v, &file_lock_list.hlist, &iter->li_cpu, pos); +} + +static void locks_stop(struct seq_file *f, void *v) + __releases(&blocked_lock_lock) +{ + spin_unlock(&blocked_lock_lock); + percpu_up_write(&file_rwsem); +} + +static const struct seq_operations locks_seq_operations = { + .start = locks_start, + .next = locks_next, + .stop = locks_stop, + .show = locks_show, +}; + +static int __init proc_locks_init(void) +{ + proc_create_seq_private("locks", 0, NULL, &locks_seq_operations, + sizeof(struct locks_iterator), NULL); + return 0; +} +fs_initcall(proc_locks_init); +#endif + +static int __init filelock_init(void) +{ + int i; + + flctx_cache = kmem_cache_create("file_lock_ctx", + sizeof(struct file_lock_context), 0, SLAB_PANIC, NULL); + + filelock_cache = kmem_cache_create("file_lock_cache", + sizeof(struct file_lock), 0, SLAB_PANIC, NULL); + + for_each_possible_cpu(i) { + struct file_lock_list_struct *fll = per_cpu_ptr(&file_lock_list, i); + + spin_lock_init(&fll->lock); + INIT_HLIST_HEAD(&fll->hlist); + } + + lease_notifier_chain_init(); + return 0; +} +core_initcall(filelock_init); |