diff options
Diffstat (limited to 'fs/fuse/dax.c')
| -rw-r--r-- | fs/fuse/dax.c | 1366 |
1 files changed, 1366 insertions, 0 deletions
diff --git a/fs/fuse/dax.c b/fs/fuse/dax.c new file mode 100644 index 000000000..2739e218d --- /dev/null +++ b/fs/fuse/dax.c @@ -0,0 +1,1366 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * dax: direct host memory access + * Copyright (C) 2020 Red Hat, Inc. + */ + +#include "fuse_i.h" + +#include <linux/delay.h> +#include <linux/dax.h> +#include <linux/uio.h> +#include <linux/pfn_t.h> +#include <linux/iomap.h> +#include <linux/interval_tree.h> + +/* + * Default memory range size. A power of 2 so it agrees with common FUSE_INIT + * map_alignment values 4KB and 64KB. + */ +#define FUSE_DAX_SHIFT 21 +#define FUSE_DAX_SZ (1 << FUSE_DAX_SHIFT) +#define FUSE_DAX_PAGES (FUSE_DAX_SZ / PAGE_SIZE) + +/* Number of ranges reclaimer will try to free in one invocation */ +#define FUSE_DAX_RECLAIM_CHUNK (10) + +/* + * Dax memory reclaim threshold in percetage of total ranges. When free + * number of free ranges drops below this threshold, reclaim can trigger + * Default is 20% + */ +#define FUSE_DAX_RECLAIM_THRESHOLD (20) + +/** Translation information for file offsets to DAX window offsets */ +struct fuse_dax_mapping { + /* Pointer to inode where this memory range is mapped */ + struct inode *inode; + + /* Will connect in fcd->free_ranges to keep track of free memory */ + struct list_head list; + + /* For interval tree in file/inode */ + struct interval_tree_node itn; + + /* Will connect in fc->busy_ranges to keep track busy memory */ + struct list_head busy_list; + + /** Position in DAX window */ + u64 window_offset; + + /** Length of mapping, in bytes */ + loff_t length; + + /* Is this mapping read-only or read-write */ + bool writable; + + /* reference count when the mapping is used by dax iomap. */ + refcount_t refcnt; +}; + +/* Per-inode dax map */ +struct fuse_inode_dax { + /* Semaphore to protect modifications to the dmap tree */ + struct rw_semaphore sem; + + /* Sorted rb tree of struct fuse_dax_mapping elements */ + struct rb_root_cached tree; + unsigned long nr; +}; + +struct fuse_conn_dax { + /* DAX device */ + struct dax_device *dev; + + /* Lock protecting accessess to members of this structure */ + spinlock_t lock; + + /* List of memory ranges which are busy */ + unsigned long nr_busy_ranges; + struct list_head busy_ranges; + + /* Worker to free up memory ranges */ + struct delayed_work free_work; + + /* Wait queue for a dax range to become free */ + wait_queue_head_t range_waitq; + + /* DAX Window Free Ranges */ + long nr_free_ranges; + struct list_head free_ranges; + + unsigned long nr_ranges; +}; + +static inline struct fuse_dax_mapping * +node_to_dmap(struct interval_tree_node *node) +{ + if (!node) + return NULL; + + return container_of(node, struct fuse_dax_mapping, itn); +} + +static struct fuse_dax_mapping * +alloc_dax_mapping_reclaim(struct fuse_conn_dax *fcd, struct inode *inode); + +static void +__kick_dmap_free_worker(struct fuse_conn_dax *fcd, unsigned long delay_ms) +{ + unsigned long free_threshold; + + /* If number of free ranges are below threshold, start reclaim */ + free_threshold = max_t(unsigned long, fcd->nr_ranges * FUSE_DAX_RECLAIM_THRESHOLD / 100, + 1); + if (fcd->nr_free_ranges < free_threshold) + queue_delayed_work(system_long_wq, &fcd->free_work, + msecs_to_jiffies(delay_ms)); +} + +static void kick_dmap_free_worker(struct fuse_conn_dax *fcd, + unsigned long delay_ms) +{ + spin_lock(&fcd->lock); + __kick_dmap_free_worker(fcd, delay_ms); + spin_unlock(&fcd->lock); +} + +static struct fuse_dax_mapping *alloc_dax_mapping(struct fuse_conn_dax *fcd) +{ + struct fuse_dax_mapping *dmap; + + spin_lock(&fcd->lock); + dmap = list_first_entry_or_null(&fcd->free_ranges, + struct fuse_dax_mapping, list); + if (dmap) { + list_del_init(&dmap->list); + WARN_ON(fcd->nr_free_ranges <= 0); + fcd->nr_free_ranges--; + } + spin_unlock(&fcd->lock); + + kick_dmap_free_worker(fcd, 0); + return dmap; +} + +/* This assumes fcd->lock is held */ +static void __dmap_remove_busy_list(struct fuse_conn_dax *fcd, + struct fuse_dax_mapping *dmap) +{ + list_del_init(&dmap->busy_list); + WARN_ON(fcd->nr_busy_ranges == 0); + fcd->nr_busy_ranges--; +} + +static void dmap_remove_busy_list(struct fuse_conn_dax *fcd, + struct fuse_dax_mapping *dmap) +{ + spin_lock(&fcd->lock); + __dmap_remove_busy_list(fcd, dmap); + spin_unlock(&fcd->lock); +} + +/* This assumes fcd->lock is held */ +static void __dmap_add_to_free_pool(struct fuse_conn_dax *fcd, + struct fuse_dax_mapping *dmap) +{ + list_add_tail(&dmap->list, &fcd->free_ranges); + fcd->nr_free_ranges++; + wake_up(&fcd->range_waitq); +} + +static void dmap_add_to_free_pool(struct fuse_conn_dax *fcd, + struct fuse_dax_mapping *dmap) +{ + /* Return fuse_dax_mapping to free list */ + spin_lock(&fcd->lock); + __dmap_add_to_free_pool(fcd, dmap); + spin_unlock(&fcd->lock); +} + +static int fuse_setup_one_mapping(struct inode *inode, unsigned long start_idx, + struct fuse_dax_mapping *dmap, bool writable, + bool upgrade) +{ + struct fuse_mount *fm = get_fuse_mount(inode); + struct fuse_conn_dax *fcd = fm->fc->dax; + struct fuse_inode *fi = get_fuse_inode(inode); + struct fuse_setupmapping_in inarg; + loff_t offset = start_idx << FUSE_DAX_SHIFT; + FUSE_ARGS(args); + ssize_t err; + + WARN_ON(fcd->nr_free_ranges < 0); + + /* Ask fuse daemon to setup mapping */ + memset(&inarg, 0, sizeof(inarg)); + inarg.foffset = offset; + inarg.fh = -1; + inarg.moffset = dmap->window_offset; + inarg.len = FUSE_DAX_SZ; + inarg.flags |= FUSE_SETUPMAPPING_FLAG_READ; + if (writable) + inarg.flags |= FUSE_SETUPMAPPING_FLAG_WRITE; + args.opcode = FUSE_SETUPMAPPING; + args.nodeid = fi->nodeid; + args.in_numargs = 1; + args.in_args[0].size = sizeof(inarg); + args.in_args[0].value = &inarg; + err = fuse_simple_request(fm, &args); + if (err < 0) + return err; + dmap->writable = writable; + if (!upgrade) { + /* + * We don't take a refernce on inode. inode is valid right now + * and when inode is going away, cleanup logic should first + * cleanup dmap entries. + */ + dmap->inode = inode; + dmap->itn.start = dmap->itn.last = start_idx; + /* Protected by fi->dax->sem */ + interval_tree_insert(&dmap->itn, &fi->dax->tree); + fi->dax->nr++; + spin_lock(&fcd->lock); + list_add_tail(&dmap->busy_list, &fcd->busy_ranges); + fcd->nr_busy_ranges++; + spin_unlock(&fcd->lock); + } + return 0; +} + +static int fuse_send_removemapping(struct inode *inode, + struct fuse_removemapping_in *inargp, + struct fuse_removemapping_one *remove_one) +{ + struct fuse_inode *fi = get_fuse_inode(inode); + struct fuse_mount *fm = get_fuse_mount(inode); + FUSE_ARGS(args); + + args.opcode = FUSE_REMOVEMAPPING; + args.nodeid = fi->nodeid; + args.in_numargs = 2; + args.in_args[0].size = sizeof(*inargp); + args.in_args[0].value = inargp; + args.in_args[1].size = inargp->count * sizeof(*remove_one); + args.in_args[1].value = remove_one; + return fuse_simple_request(fm, &args); +} + +static int dmap_removemapping_list(struct inode *inode, unsigned int num, + struct list_head *to_remove) +{ + struct fuse_removemapping_one *remove_one, *ptr; + struct fuse_removemapping_in inarg; + struct fuse_dax_mapping *dmap; + int ret, i = 0, nr_alloc; + + nr_alloc = min_t(unsigned int, num, FUSE_REMOVEMAPPING_MAX_ENTRY); + remove_one = kmalloc_array(nr_alloc, sizeof(*remove_one), GFP_NOFS); + if (!remove_one) + return -ENOMEM; + + ptr = remove_one; + list_for_each_entry(dmap, to_remove, list) { + ptr->moffset = dmap->window_offset; + ptr->len = dmap->length; + ptr++; + i++; + num--; + if (i >= nr_alloc || num == 0) { + memset(&inarg, 0, sizeof(inarg)); + inarg.count = i; + ret = fuse_send_removemapping(inode, &inarg, + remove_one); + if (ret) + goto out; + ptr = remove_one; + i = 0; + } + } +out: + kfree(remove_one); + return ret; +} + +/* + * Cleanup dmap entry and add back to free list. This should be called with + * fcd->lock held. + */ +static void dmap_reinit_add_to_free_pool(struct fuse_conn_dax *fcd, + struct fuse_dax_mapping *dmap) +{ + pr_debug("fuse: freeing memory range start_idx=0x%lx end_idx=0x%lx window_offset=0x%llx length=0x%llx\n", + dmap->itn.start, dmap->itn.last, dmap->window_offset, + dmap->length); + __dmap_remove_busy_list(fcd, dmap); + dmap->inode = NULL; + dmap->itn.start = dmap->itn.last = 0; + __dmap_add_to_free_pool(fcd, dmap); +} + +/* + * Free inode dmap entries whose range falls inside [start, end]. + * Does not take any locks. At this point of time it should only be + * called from evict_inode() path where we know all dmap entries can be + * reclaimed. + */ +static void inode_reclaim_dmap_range(struct fuse_conn_dax *fcd, + struct inode *inode, + loff_t start, loff_t end) +{ + struct fuse_inode *fi = get_fuse_inode(inode); + struct fuse_dax_mapping *dmap, *n; + int err, num = 0; + LIST_HEAD(to_remove); + unsigned long start_idx = start >> FUSE_DAX_SHIFT; + unsigned long end_idx = end >> FUSE_DAX_SHIFT; + struct interval_tree_node *node; + + while (1) { + node = interval_tree_iter_first(&fi->dax->tree, start_idx, + end_idx); + if (!node) + break; + dmap = node_to_dmap(node); + /* inode is going away. There should not be any users of dmap */ + WARN_ON(refcount_read(&dmap->refcnt) > 1); + interval_tree_remove(&dmap->itn, &fi->dax->tree); + num++; + list_add(&dmap->list, &to_remove); + } + + /* Nothing to remove */ + if (list_empty(&to_remove)) + return; + + WARN_ON(fi->dax->nr < num); + fi->dax->nr -= num; + err = dmap_removemapping_list(inode, num, &to_remove); + if (err && err != -ENOTCONN) { + pr_warn("Failed to removemappings. start=0x%llx end=0x%llx\n", + start, end); + } + spin_lock(&fcd->lock); + list_for_each_entry_safe(dmap, n, &to_remove, list) { + list_del_init(&dmap->list); + dmap_reinit_add_to_free_pool(fcd, dmap); + } + spin_unlock(&fcd->lock); +} + +static int dmap_removemapping_one(struct inode *inode, + struct fuse_dax_mapping *dmap) +{ + struct fuse_removemapping_one forget_one; + struct fuse_removemapping_in inarg; + + memset(&inarg, 0, sizeof(inarg)); + inarg.count = 1; + memset(&forget_one, 0, sizeof(forget_one)); + forget_one.moffset = dmap->window_offset; + forget_one.len = dmap->length; + + return fuse_send_removemapping(inode, &inarg, &forget_one); +} + +/* + * It is called from evict_inode() and by that time inode is going away. So + * this function does not take any locks like fi->dax->sem for traversing + * that fuse inode interval tree. If that lock is taken then lock validator + * complains of deadlock situation w.r.t fs_reclaim lock. + */ +void fuse_dax_inode_cleanup(struct inode *inode) +{ + struct fuse_conn *fc = get_fuse_conn(inode); + struct fuse_inode *fi = get_fuse_inode(inode); + + /* + * fuse_evict_inode() has already called truncate_inode_pages_final() + * before we arrive here. So we should not have to worry about any + * pages/exception entries still associated with inode. + */ + inode_reclaim_dmap_range(fc->dax, inode, 0, -1); + WARN_ON(fi->dax->nr); +} + +static void fuse_fill_iomap_hole(struct iomap *iomap, loff_t length) +{ + iomap->addr = IOMAP_NULL_ADDR; + iomap->length = length; + iomap->type = IOMAP_HOLE; +} + +static void fuse_fill_iomap(struct inode *inode, loff_t pos, loff_t length, + struct iomap *iomap, struct fuse_dax_mapping *dmap, + unsigned int flags) +{ + loff_t offset, len; + loff_t i_size = i_size_read(inode); + + offset = pos - (dmap->itn.start << FUSE_DAX_SHIFT); + len = min(length, dmap->length - offset); + + /* If length is beyond end of file, truncate further */ + if (pos + len > i_size) + len = i_size - pos; + + if (len > 0) { + iomap->addr = dmap->window_offset + offset; + iomap->length = len; + if (flags & IOMAP_FAULT) + iomap->length = ALIGN(len, PAGE_SIZE); + iomap->type = IOMAP_MAPPED; + /* + * increace refcnt so that reclaim code knows this dmap is in + * use. This assumes fi->dax->sem mutex is held either + * shared/exclusive. + */ + refcount_inc(&dmap->refcnt); + + /* iomap->private should be NULL */ + WARN_ON_ONCE(iomap->private); + iomap->private = dmap; + } else { + /* Mapping beyond end of file is hole */ + fuse_fill_iomap_hole(iomap, length); + } +} + +static int fuse_setup_new_dax_mapping(struct inode *inode, loff_t pos, + loff_t length, unsigned int flags, + struct iomap *iomap) +{ + struct fuse_inode *fi = get_fuse_inode(inode); + struct fuse_conn *fc = get_fuse_conn(inode); + struct fuse_conn_dax *fcd = fc->dax; + struct fuse_dax_mapping *dmap, *alloc_dmap = NULL; + int ret; + bool writable = flags & IOMAP_WRITE; + unsigned long start_idx = pos >> FUSE_DAX_SHIFT; + struct interval_tree_node *node; + + /* + * Can't do inline reclaim in fault path. We call + * dax_layout_busy_page() before we free a range. And + * fuse_wait_dax_page() drops fi->i_mmap_sem lock and requires it. + * In fault path we enter with fi->i_mmap_sem held and can't drop + * it. Also in fault path we hold fi->i_mmap_sem shared and not + * exclusive, so that creates further issues with fuse_wait_dax_page(). + * Hence return -EAGAIN and fuse_dax_fault() will wait for a memory + * range to become free and retry. + */ + if (flags & IOMAP_FAULT) { + alloc_dmap = alloc_dax_mapping(fcd); + if (!alloc_dmap) + return -EAGAIN; + } else { + alloc_dmap = alloc_dax_mapping_reclaim(fcd, inode); + if (IS_ERR(alloc_dmap)) + return PTR_ERR(alloc_dmap); + } + + /* If we are here, we should have memory allocated */ + if (WARN_ON(!alloc_dmap)) + return -EIO; + + /* + * Take write lock so that only one caller can try to setup mapping + * and other waits. + */ + down_write(&fi->dax->sem); + /* + * We dropped lock. Check again if somebody else setup + * mapping already. + */ + node = interval_tree_iter_first(&fi->dax->tree, start_idx, start_idx); + if (node) { + dmap = node_to_dmap(node); + fuse_fill_iomap(inode, pos, length, iomap, dmap, flags); + dmap_add_to_free_pool(fcd, alloc_dmap); + up_write(&fi->dax->sem); + return 0; + } + + /* Setup one mapping */ + ret = fuse_setup_one_mapping(inode, pos >> FUSE_DAX_SHIFT, alloc_dmap, + writable, false); + if (ret < 0) { + dmap_add_to_free_pool(fcd, alloc_dmap); + up_write(&fi->dax->sem); + return ret; + } + fuse_fill_iomap(inode, pos, length, iomap, alloc_dmap, flags); + up_write(&fi->dax->sem); + return 0; +} + +static int fuse_upgrade_dax_mapping(struct inode *inode, loff_t pos, + loff_t length, unsigned int flags, + struct iomap *iomap) +{ + struct fuse_inode *fi = get_fuse_inode(inode); + struct fuse_dax_mapping *dmap; + int ret; + unsigned long idx = pos >> FUSE_DAX_SHIFT; + struct interval_tree_node *node; + + /* + * Take exclusive lock so that only one caller can try to setup + * mapping and others wait. + */ + down_write(&fi->dax->sem); + node = interval_tree_iter_first(&fi->dax->tree, idx, idx); + + /* We are holding either inode lock or i_mmap_sem, and that should + * ensure that dmap can't be truncated. We are holding a reference + * on dmap and that should make sure it can't be reclaimed. So dmap + * should still be there in tree despite the fact we dropped and + * re-acquired the fi->dax->sem lock. + */ + ret = -EIO; + if (WARN_ON(!node)) + goto out_err; + + dmap = node_to_dmap(node); + + /* We took an extra reference on dmap to make sure its not reclaimd. + * Now we hold fi->dax->sem lock and that reference is not needed + * anymore. Drop it. + */ + if (refcount_dec_and_test(&dmap->refcnt)) { + /* refcount should not hit 0. This object only goes + * away when fuse connection goes away + */ + WARN_ON_ONCE(1); + } + + /* Maybe another thread already upgraded mapping while we were not + * holding lock. + */ + if (dmap->writable) { + ret = 0; + goto out_fill_iomap; + } + + ret = fuse_setup_one_mapping(inode, pos >> FUSE_DAX_SHIFT, dmap, true, + true); + if (ret < 0) + goto out_err; +out_fill_iomap: + fuse_fill_iomap(inode, pos, length, iomap, dmap, flags); +out_err: + up_write(&fi->dax->sem); + return ret; +} + +/* This is just for DAX and the mapping is ephemeral, do not use it for other + * purposes since there is no block device with a permanent mapping. + */ +static int fuse_iomap_begin(struct inode *inode, loff_t pos, loff_t length, + unsigned int flags, struct iomap *iomap, + struct iomap *srcmap) +{ + struct fuse_inode *fi = get_fuse_inode(inode); + struct fuse_conn *fc = get_fuse_conn(inode); + struct fuse_dax_mapping *dmap; + bool writable = flags & IOMAP_WRITE; + unsigned long start_idx = pos >> FUSE_DAX_SHIFT; + struct interval_tree_node *node; + + /* We don't support FIEMAP */ + if (WARN_ON(flags & IOMAP_REPORT)) + return -EIO; + + iomap->offset = pos; + iomap->flags = 0; + iomap->bdev = NULL; + iomap->dax_dev = fc->dax->dev; + + /* + * Both read/write and mmap path can race here. So we need something + * to make sure if we are setting up mapping, then other path waits + * + * For now, use a semaphore for this. It probably needs to be + * optimized later. + */ + down_read(&fi->dax->sem); + node = interval_tree_iter_first(&fi->dax->tree, start_idx, start_idx); + if (node) { + dmap = node_to_dmap(node); + if (writable && !dmap->writable) { + /* Upgrade read-only mapping to read-write. This will + * require exclusive fi->dax->sem lock as we don't want + * two threads to be trying to this simultaneously + * for same dmap. So drop shared lock and acquire + * exclusive lock. + * + * Before dropping fi->dax->sem lock, take reference + * on dmap so that its not freed by range reclaim. + */ + refcount_inc(&dmap->refcnt); + up_read(&fi->dax->sem); + pr_debug("%s: Upgrading mapping at offset 0x%llx length 0x%llx\n", + __func__, pos, length); + return fuse_upgrade_dax_mapping(inode, pos, length, + flags, iomap); + } else { + fuse_fill_iomap(inode, pos, length, iomap, dmap, flags); + up_read(&fi->dax->sem); + return 0; + } + } else { + up_read(&fi->dax->sem); + pr_debug("%s: no mapping at offset 0x%llx length 0x%llx\n", + __func__, pos, length); + if (pos >= i_size_read(inode)) + goto iomap_hole; + + return fuse_setup_new_dax_mapping(inode, pos, length, flags, + iomap); + } + + /* + * If read beyond end of file happnes, fs code seems to return + * it as hole + */ +iomap_hole: + fuse_fill_iomap_hole(iomap, length); + pr_debug("%s returning hole mapping. pos=0x%llx length_asked=0x%llx length_returned=0x%llx\n", + __func__, pos, length, iomap->length); + return 0; +} + +static int fuse_iomap_end(struct inode *inode, loff_t pos, loff_t length, + ssize_t written, unsigned int flags, + struct iomap *iomap) +{ + struct fuse_dax_mapping *dmap = iomap->private; + + if (dmap) { + if (refcount_dec_and_test(&dmap->refcnt)) { + /* refcount should not hit 0. This object only goes + * away when fuse connection goes away + */ + WARN_ON_ONCE(1); + } + } + + /* DAX writes beyond end-of-file aren't handled using iomap, so the + * file size is unchanged and there is nothing to do here. + */ + return 0; +} + +static const struct iomap_ops fuse_iomap_ops = { + .iomap_begin = fuse_iomap_begin, + .iomap_end = fuse_iomap_end, +}; + +static void fuse_wait_dax_page(struct inode *inode) +{ + struct fuse_inode *fi = get_fuse_inode(inode); + + up_write(&fi->i_mmap_sem); + schedule(); + down_write(&fi->i_mmap_sem); +} + +/* Should be called with fi->i_mmap_sem lock held exclusively */ +static int __fuse_dax_break_layouts(struct inode *inode, bool *retry, + loff_t start, loff_t end) +{ + struct page *page; + + page = dax_layout_busy_page_range(inode->i_mapping, start, end); + if (!page) + return 0; + + *retry = true; + return ___wait_var_event(&page->_refcount, + atomic_read(&page->_refcount) == 1, TASK_INTERRUPTIBLE, + 0, 0, fuse_wait_dax_page(inode)); +} + +/* dmap_end == 0 leads to unmapping of whole file */ +int fuse_dax_break_layouts(struct inode *inode, u64 dmap_start, + u64 dmap_end) +{ + bool retry; + int ret; + + do { + retry = false; + ret = __fuse_dax_break_layouts(inode, &retry, dmap_start, + dmap_end); + } while (ret == 0 && retry); + + return ret; +} + +ssize_t fuse_dax_read_iter(struct kiocb *iocb, struct iov_iter *to) +{ + struct inode *inode = file_inode(iocb->ki_filp); + ssize_t ret; + + if (iocb->ki_flags & IOCB_NOWAIT) { + if (!inode_trylock_shared(inode)) + return -EAGAIN; + } else { + inode_lock_shared(inode); + } + + ret = dax_iomap_rw(iocb, to, &fuse_iomap_ops); + inode_unlock_shared(inode); + + /* TODO file_accessed(iocb->f_filp) */ + return ret; +} + +static bool file_extending_write(struct kiocb *iocb, struct iov_iter *from) +{ + struct inode *inode = file_inode(iocb->ki_filp); + + return (iov_iter_rw(from) == WRITE && + ((iocb->ki_pos) >= i_size_read(inode) || + (iocb->ki_pos + iov_iter_count(from) > i_size_read(inode)))); +} + +static ssize_t fuse_dax_direct_write(struct kiocb *iocb, struct iov_iter *from) +{ + struct inode *inode = file_inode(iocb->ki_filp); + struct fuse_io_priv io = FUSE_IO_PRIV_SYNC(iocb); + ssize_t ret; + + ret = fuse_direct_io(&io, from, &iocb->ki_pos, FUSE_DIO_WRITE); + if (ret < 0) + return ret; + + fuse_invalidate_attr(inode); + fuse_write_update_size(inode, iocb->ki_pos); + return ret; +} + +ssize_t fuse_dax_write_iter(struct kiocb *iocb, struct iov_iter *from) +{ + struct inode *inode = file_inode(iocb->ki_filp); + ssize_t ret; + + if (iocb->ki_flags & IOCB_NOWAIT) { + if (!inode_trylock(inode)) + return -EAGAIN; + } else { + inode_lock(inode); + } + + ret = generic_write_checks(iocb, from); + if (ret <= 0) + goto out; + + ret = file_remove_privs(iocb->ki_filp); + if (ret) + goto out; + /* TODO file_update_time() but we don't want metadata I/O */ + + /* Do not use dax for file extending writes as write and on + * disk i_size increase are not atomic otherwise. + */ + if (file_extending_write(iocb, from)) + ret = fuse_dax_direct_write(iocb, from); + else + ret = dax_iomap_rw(iocb, from, &fuse_iomap_ops); + +out: + inode_unlock(inode); + + if (ret > 0) + ret = generic_write_sync(iocb, ret); + return ret; +} + +static int fuse_dax_writepages(struct address_space *mapping, + struct writeback_control *wbc) +{ + + struct inode *inode = mapping->host; + struct fuse_conn *fc = get_fuse_conn(inode); + + return dax_writeback_mapping_range(mapping, fc->dax->dev, wbc); +} + +static vm_fault_t __fuse_dax_fault(struct vm_fault *vmf, + enum page_entry_size pe_size, bool write) +{ + vm_fault_t ret; + struct inode *inode = file_inode(vmf->vma->vm_file); + struct super_block *sb = inode->i_sb; + pfn_t pfn; + int error = 0; + struct fuse_conn *fc = get_fuse_conn(inode); + struct fuse_conn_dax *fcd = fc->dax; + bool retry = false; + + if (write) + sb_start_pagefault(sb); +retry: + if (retry && !(fcd->nr_free_ranges > 0)) + wait_event(fcd->range_waitq, (fcd->nr_free_ranges > 0)); + + /* + * We need to serialize against not only truncate but also against + * fuse dax memory range reclaim. While a range is being reclaimed, + * we do not want any read/write/mmap to make progress and try + * to populate page cache or access memory we are trying to free. + */ + down_read(&get_fuse_inode(inode)->i_mmap_sem); + ret = dax_iomap_fault(vmf, pe_size, &pfn, &error, &fuse_iomap_ops); + if ((ret & VM_FAULT_ERROR) && error == -EAGAIN) { + error = 0; + retry = true; + up_read(&get_fuse_inode(inode)->i_mmap_sem); + goto retry; + } + + if (ret & VM_FAULT_NEEDDSYNC) + ret = dax_finish_sync_fault(vmf, pe_size, pfn); + up_read(&get_fuse_inode(inode)->i_mmap_sem); + + if (write) + sb_end_pagefault(sb); + + return ret; +} + +static vm_fault_t fuse_dax_fault(struct vm_fault *vmf) +{ + return __fuse_dax_fault(vmf, PE_SIZE_PTE, + vmf->flags & FAULT_FLAG_WRITE); +} + +static vm_fault_t fuse_dax_huge_fault(struct vm_fault *vmf, + enum page_entry_size pe_size) +{ + return __fuse_dax_fault(vmf, pe_size, vmf->flags & FAULT_FLAG_WRITE); +} + +static vm_fault_t fuse_dax_page_mkwrite(struct vm_fault *vmf) +{ + return __fuse_dax_fault(vmf, PE_SIZE_PTE, true); +} + +static vm_fault_t fuse_dax_pfn_mkwrite(struct vm_fault *vmf) +{ + return __fuse_dax_fault(vmf, PE_SIZE_PTE, true); +} + +static const struct vm_operations_struct fuse_dax_vm_ops = { + .fault = fuse_dax_fault, + .huge_fault = fuse_dax_huge_fault, + .page_mkwrite = fuse_dax_page_mkwrite, + .pfn_mkwrite = fuse_dax_pfn_mkwrite, +}; + +int fuse_dax_mmap(struct file *file, struct vm_area_struct *vma) +{ + file_accessed(file); + vma->vm_ops = &fuse_dax_vm_ops; + vma->vm_flags |= VM_MIXEDMAP | VM_HUGEPAGE; + return 0; +} + +static int dmap_writeback_invalidate(struct inode *inode, + struct fuse_dax_mapping *dmap) +{ + int ret; + loff_t start_pos = dmap->itn.start << FUSE_DAX_SHIFT; + loff_t end_pos = (start_pos + FUSE_DAX_SZ - 1); + + ret = filemap_fdatawrite_range(inode->i_mapping, start_pos, end_pos); + if (ret) { + pr_debug("fuse: filemap_fdatawrite_range() failed. err=%d start_pos=0x%llx, end_pos=0x%llx\n", + ret, start_pos, end_pos); + return ret; + } + + ret = invalidate_inode_pages2_range(inode->i_mapping, + start_pos >> PAGE_SHIFT, + end_pos >> PAGE_SHIFT); + if (ret) + pr_debug("fuse: invalidate_inode_pages2_range() failed err=%d\n", + ret); + + return ret; +} + +static int reclaim_one_dmap_locked(struct inode *inode, + struct fuse_dax_mapping *dmap) +{ + int ret; + struct fuse_inode *fi = get_fuse_inode(inode); + + /* + * igrab() was done to make sure inode won't go under us, and this + * further avoids the race with evict(). + */ + ret = dmap_writeback_invalidate(inode, dmap); + if (ret) + return ret; + + /* Remove dax mapping from inode interval tree now */ + interval_tree_remove(&dmap->itn, &fi->dax->tree); + fi->dax->nr--; + + /* It is possible that umount/shutdown has killed the fuse connection + * and worker thread is trying to reclaim memory in parallel. Don't + * warn in that case. + */ + ret = dmap_removemapping_one(inode, dmap); + if (ret && ret != -ENOTCONN) { + pr_warn("Failed to remove mapping. offset=0x%llx len=0x%llx ret=%d\n", + dmap->window_offset, dmap->length, ret); + } + return 0; +} + +/* Find first mapped dmap for an inode and return file offset. Caller needs + * to hold fi->dax->sem lock either shared or exclusive. + */ +static struct fuse_dax_mapping *inode_lookup_first_dmap(struct inode *inode) +{ + struct fuse_inode *fi = get_fuse_inode(inode); + struct fuse_dax_mapping *dmap; + struct interval_tree_node *node; + + for (node = interval_tree_iter_first(&fi->dax->tree, 0, -1); node; + node = interval_tree_iter_next(node, 0, -1)) { + dmap = node_to_dmap(node); + /* still in use. */ + if (refcount_read(&dmap->refcnt) > 1) + continue; + + return dmap; + } + + return NULL; +} + +/* + * Find first mapping in the tree and free it and return it. Do not add + * it back to free pool. + */ +static struct fuse_dax_mapping * +inode_inline_reclaim_one_dmap(struct fuse_conn_dax *fcd, struct inode *inode, + bool *retry) +{ + struct fuse_inode *fi = get_fuse_inode(inode); + struct fuse_dax_mapping *dmap; + u64 dmap_start, dmap_end; + unsigned long start_idx; + int ret; + struct interval_tree_node *node; + + down_write(&fi->i_mmap_sem); + + /* Lookup a dmap and corresponding file offset to reclaim. */ + down_read(&fi->dax->sem); + dmap = inode_lookup_first_dmap(inode); + if (dmap) { + start_idx = dmap->itn.start; + dmap_start = start_idx << FUSE_DAX_SHIFT; + dmap_end = dmap_start + FUSE_DAX_SZ - 1; + } + up_read(&fi->dax->sem); + + if (!dmap) + goto out_mmap_sem; + /* + * Make sure there are no references to inode pages using + * get_user_pages() + */ + ret = fuse_dax_break_layouts(inode, dmap_start, dmap_end); + if (ret) { + pr_debug("fuse: fuse_dax_break_layouts() failed. err=%d\n", + ret); + dmap = ERR_PTR(ret); + goto out_mmap_sem; + } + + down_write(&fi->dax->sem); + node = interval_tree_iter_first(&fi->dax->tree, start_idx, start_idx); + /* Range already got reclaimed by somebody else */ + if (!node) { + if (retry) + *retry = true; + goto out_write_dmap_sem; + } + + dmap = node_to_dmap(node); + /* still in use. */ + if (refcount_read(&dmap->refcnt) > 1) { + dmap = NULL; + if (retry) + *retry = true; + goto out_write_dmap_sem; + } + + ret = reclaim_one_dmap_locked(inode, dmap); + if (ret < 0) { + dmap = ERR_PTR(ret); + goto out_write_dmap_sem; + } + + /* Clean up dmap. Do not add back to free list */ + dmap_remove_busy_list(fcd, dmap); + dmap->inode = NULL; + dmap->itn.start = dmap->itn.last = 0; + + pr_debug("fuse: %s: inline reclaimed memory range. inode=%p, window_offset=0x%llx, length=0x%llx\n", + __func__, inode, dmap->window_offset, dmap->length); + +out_write_dmap_sem: + up_write(&fi->dax->sem); +out_mmap_sem: + up_write(&fi->i_mmap_sem); + return dmap; +} + +static struct fuse_dax_mapping * +alloc_dax_mapping_reclaim(struct fuse_conn_dax *fcd, struct inode *inode) +{ + struct fuse_dax_mapping *dmap; + struct fuse_inode *fi = get_fuse_inode(inode); + + while (1) { + bool retry = false; + + dmap = alloc_dax_mapping(fcd); + if (dmap) + return dmap; + + dmap = inode_inline_reclaim_one_dmap(fcd, inode, &retry); + /* + * Either we got a mapping or it is an error, return in both + * the cases. + */ + if (dmap) + return dmap; + + /* If we could not reclaim a mapping because it + * had a reference or some other temporary failure, + * Try again. We want to give up inline reclaim only + * if there is no range assigned to this node. Otherwise + * if a deadlock is possible if we sleep with fi->i_mmap_sem + * held and worker to free memory can't make progress due + * to unavailability of fi->i_mmap_sem lock. So sleep + * only if fi->dax->nr=0 + */ + if (retry) + continue; + /* + * There are no mappings which can be reclaimed. Wait for one. + * We are not holding fi->dax->sem. So it is possible + * that range gets added now. But as we are not holding + * fi->i_mmap_sem, worker should still be able to free up + * a range and wake us up. + */ + if (!fi->dax->nr && !(fcd->nr_free_ranges > 0)) { + if (wait_event_killable_exclusive(fcd->range_waitq, + (fcd->nr_free_ranges > 0))) { + return ERR_PTR(-EINTR); + } + } + } +} + +static int lookup_and_reclaim_dmap_locked(struct fuse_conn_dax *fcd, + struct inode *inode, + unsigned long start_idx) +{ + int ret; + struct fuse_inode *fi = get_fuse_inode(inode); + struct fuse_dax_mapping *dmap; + struct interval_tree_node *node; + + /* Find fuse dax mapping at file offset inode. */ + node = interval_tree_iter_first(&fi->dax->tree, start_idx, start_idx); + + /* Range already got cleaned up by somebody else */ + if (!node) + return 0; + dmap = node_to_dmap(node); + + /* still in use. */ + if (refcount_read(&dmap->refcnt) > 1) + return 0; + + ret = reclaim_one_dmap_locked(inode, dmap); + if (ret < 0) + return ret; + + /* Cleanup dmap entry and add back to free list */ + spin_lock(&fcd->lock); + dmap_reinit_add_to_free_pool(fcd, dmap); + spin_unlock(&fcd->lock); + return ret; +} + +/* + * Free a range of memory. + * Locking: + * 1. Take fi->i_mmap_sem to block dax faults. + * 2. Take fi->dax->sem to protect interval tree and also to make sure + * read/write can not reuse a dmap which we might be freeing. + */ +static int lookup_and_reclaim_dmap(struct fuse_conn_dax *fcd, + struct inode *inode, + unsigned long start_idx, + unsigned long end_idx) +{ + int ret; + struct fuse_inode *fi = get_fuse_inode(inode); + loff_t dmap_start = start_idx << FUSE_DAX_SHIFT; + loff_t dmap_end = (dmap_start + FUSE_DAX_SZ) - 1; + + down_write(&fi->i_mmap_sem); + ret = fuse_dax_break_layouts(inode, dmap_start, dmap_end); + if (ret) { + pr_debug("virtio_fs: fuse_dax_break_layouts() failed. err=%d\n", + ret); + goto out_mmap_sem; + } + + down_write(&fi->dax->sem); + ret = lookup_and_reclaim_dmap_locked(fcd, inode, start_idx); + up_write(&fi->dax->sem); +out_mmap_sem: + up_write(&fi->i_mmap_sem); + return ret; +} + +static int try_to_free_dmap_chunks(struct fuse_conn_dax *fcd, + unsigned long nr_to_free) +{ + struct fuse_dax_mapping *dmap, *pos, *temp; + int ret, nr_freed = 0; + unsigned long start_idx = 0, end_idx = 0; + struct inode *inode = NULL; + + /* Pick first busy range and free it for now*/ + while (1) { + if (nr_freed >= nr_to_free) + break; + + dmap = NULL; + spin_lock(&fcd->lock); + + if (!fcd->nr_busy_ranges) { + spin_unlock(&fcd->lock); + return 0; + } + + list_for_each_entry_safe(pos, temp, &fcd->busy_ranges, + busy_list) { + /* skip this range if it's in use. */ + if (refcount_read(&pos->refcnt) > 1) + continue; + + inode = igrab(pos->inode); + /* + * This inode is going away. That will free + * up all the ranges anyway, continue to + * next range. + */ + if (!inode) + continue; + /* + * Take this element off list and add it tail. If + * this element can't be freed, it will help with + * selecting new element in next iteration of loop. + */ + dmap = pos; + list_move_tail(&dmap->busy_list, &fcd->busy_ranges); + start_idx = end_idx = dmap->itn.start; + break; + } + spin_unlock(&fcd->lock); + if (!dmap) + return 0; + + ret = lookup_and_reclaim_dmap(fcd, inode, start_idx, end_idx); + iput(inode); + if (ret) + return ret; + nr_freed++; + } + return 0; +} + +static void fuse_dax_free_mem_worker(struct work_struct *work) +{ + int ret; + struct fuse_conn_dax *fcd = container_of(work, struct fuse_conn_dax, + free_work.work); + ret = try_to_free_dmap_chunks(fcd, FUSE_DAX_RECLAIM_CHUNK); + if (ret) { + pr_debug("fuse: try_to_free_dmap_chunks() failed with err=%d\n", + ret); + } + + /* If number of free ranges are still below threhold, requeue */ + kick_dmap_free_worker(fcd, 1); +} + +static void fuse_free_dax_mem_ranges(struct list_head *mem_list) +{ + struct fuse_dax_mapping *range, *temp; + + /* Free All allocated elements */ + list_for_each_entry_safe(range, temp, mem_list, list) { + list_del(&range->list); + if (!list_empty(&range->busy_list)) + list_del(&range->busy_list); + kfree(range); + } +} + +void fuse_dax_conn_free(struct fuse_conn *fc) +{ + if (fc->dax) { + fuse_free_dax_mem_ranges(&fc->dax->free_ranges); + kfree(fc->dax); + fc->dax = NULL; + } +} + +static int fuse_dax_mem_range_init(struct fuse_conn_dax *fcd) +{ + long nr_pages, nr_ranges; + void *kaddr; + pfn_t pfn; + struct fuse_dax_mapping *range; + int ret, id; + size_t dax_size = -1; + unsigned long i; + + init_waitqueue_head(&fcd->range_waitq); + INIT_LIST_HEAD(&fcd->free_ranges); + INIT_LIST_HEAD(&fcd->busy_ranges); + INIT_DELAYED_WORK(&fcd->free_work, fuse_dax_free_mem_worker); + + id = dax_read_lock(); + nr_pages = dax_direct_access(fcd->dev, 0, PHYS_PFN(dax_size), &kaddr, + &pfn); + dax_read_unlock(id); + if (nr_pages < 0) { + pr_debug("dax_direct_access() returned %ld\n", nr_pages); + return nr_pages; + } + + nr_ranges = nr_pages/FUSE_DAX_PAGES; + pr_debug("%s: dax mapped %ld pages. nr_ranges=%ld\n", + __func__, nr_pages, nr_ranges); + + for (i = 0; i < nr_ranges; i++) { + range = kzalloc(sizeof(struct fuse_dax_mapping), GFP_KERNEL); + ret = -ENOMEM; + if (!range) + goto out_err; + + /* TODO: This offset only works if virtio-fs driver is not + * having some memory hidden at the beginning. This needs + * better handling + */ + range->window_offset = i * FUSE_DAX_SZ; + range->length = FUSE_DAX_SZ; + INIT_LIST_HEAD(&range->busy_list); + refcount_set(&range->refcnt, 1); + list_add_tail(&range->list, &fcd->free_ranges); + } + + fcd->nr_free_ranges = nr_ranges; + fcd->nr_ranges = nr_ranges; + return 0; +out_err: + /* Free All allocated elements */ + fuse_free_dax_mem_ranges(&fcd->free_ranges); + return ret; +} + +int fuse_dax_conn_alloc(struct fuse_conn *fc, struct dax_device *dax_dev) +{ + struct fuse_conn_dax *fcd; + int err; + + if (!dax_dev) + return 0; + + fcd = kzalloc(sizeof(*fcd), GFP_KERNEL); + if (!fcd) + return -ENOMEM; + + spin_lock_init(&fcd->lock); + fcd->dev = dax_dev; + err = fuse_dax_mem_range_init(fcd); + if (err) { + kfree(fcd); + return err; + } + + fc->dax = fcd; + return 0; +} + +bool fuse_dax_inode_alloc(struct super_block *sb, struct fuse_inode *fi) +{ + struct fuse_conn *fc = get_fuse_conn_super(sb); + + fi->dax = NULL; + if (fc->dax) { + fi->dax = kzalloc(sizeof(*fi->dax), GFP_KERNEL_ACCOUNT); + if (!fi->dax) + return false; + + init_rwsem(&fi->dax->sem); + fi->dax->tree = RB_ROOT_CACHED; + } + + return true; +} + +static const struct address_space_operations fuse_dax_file_aops = { + .writepages = fuse_dax_writepages, + .direct_IO = noop_direct_IO, + .set_page_dirty = noop_set_page_dirty, + .invalidatepage = noop_invalidatepage, +}; + +void fuse_dax_inode_init(struct inode *inode) +{ + struct fuse_conn *fc = get_fuse_conn(inode); + + if (!fc->dax) + return; + + inode->i_flags |= S_DAX; + inode->i_data.a_ops = &fuse_dax_file_aops; +} + +bool fuse_dax_check_alignment(struct fuse_conn *fc, unsigned int map_alignment) +{ + if (fc->dax && (map_alignment > FUSE_DAX_SHIFT)) { + pr_warn("FUSE: map_alignment %u incompatible with dax mem range size %u\n", + map_alignment, FUSE_DAX_SZ); + return false; + } + return true; +} + +void fuse_dax_cancel_work(struct fuse_conn *fc) +{ + struct fuse_conn_dax *fcd = fc->dax; + + if (fcd) + cancel_delayed_work_sync(&fcd->free_work); + +} +EXPORT_SYMBOL_GPL(fuse_dax_cancel_work); |