diff options
Diffstat (limited to 'mm/mlock.c')
| -rw-r--r-- | mm/mlock.c | 785 |
1 files changed, 785 insertions, 0 deletions
diff --git a/mm/mlock.c b/mm/mlock.c new file mode 100644 index 000000000..06bdfab83 --- /dev/null +++ b/mm/mlock.c @@ -0,0 +1,785 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * linux/mm/mlock.c + * + * (C) Copyright 1995 Linus Torvalds + * (C) Copyright 2002 Christoph Hellwig + */ + +#include <linux/capability.h> +#include <linux/mman.h> +#include <linux/mm.h> +#include <linux/sched/user.h> +#include <linux/swap.h> +#include <linux/swapops.h> +#include <linux/pagemap.h> +#include <linux/pagevec.h> +#include <linux/pagewalk.h> +#include <linux/mempolicy.h> +#include <linux/syscalls.h> +#include <linux/sched.h> +#include <linux/export.h> +#include <linux/rmap.h> +#include <linux/mmzone.h> +#include <linux/hugetlb.h> +#include <linux/memcontrol.h> +#include <linux/mm_inline.h> +#include <linux/secretmem.h> + +#include "internal.h" + +struct mlock_fbatch { + local_lock_t lock; + struct folio_batch fbatch; +}; + +static DEFINE_PER_CPU(struct mlock_fbatch, mlock_fbatch) = { + .lock = INIT_LOCAL_LOCK(lock), +}; + +bool can_do_mlock(void) +{ + if (rlimit(RLIMIT_MEMLOCK) != 0) + return true; + if (capable(CAP_IPC_LOCK)) + return true; + return false; +} +EXPORT_SYMBOL(can_do_mlock); + +/* + * Mlocked folios are marked with the PG_mlocked flag for efficient testing + * in vmscan and, possibly, the fault path; and to support semi-accurate + * statistics. + * + * An mlocked folio [folio_test_mlocked(folio)] is unevictable. As such, it + * will be ostensibly placed on the LRU "unevictable" list (actually no such + * list exists), rather than the [in]active lists. PG_unevictable is set to + * indicate the unevictable state. + */ + +static struct lruvec *__mlock_folio(struct folio *folio, struct lruvec *lruvec) +{ + /* There is nothing more we can do while it's off LRU */ + if (!folio_test_clear_lru(folio)) + return lruvec; + + lruvec = folio_lruvec_relock_irq(folio, lruvec); + + if (unlikely(folio_evictable(folio))) { + /* + * This is a little surprising, but quite possible: PG_mlocked + * must have got cleared already by another CPU. Could this + * folio be unevictable? I'm not sure, but move it now if so. + */ + if (folio_test_unevictable(folio)) { + lruvec_del_folio(lruvec, folio); + folio_clear_unevictable(folio); + lruvec_add_folio(lruvec, folio); + + __count_vm_events(UNEVICTABLE_PGRESCUED, + folio_nr_pages(folio)); + } + goto out; + } + + if (folio_test_unevictable(folio)) { + if (folio_test_mlocked(folio)) + folio->mlock_count++; + goto out; + } + + lruvec_del_folio(lruvec, folio); + folio_clear_active(folio); + folio_set_unevictable(folio); + folio->mlock_count = !!folio_test_mlocked(folio); + lruvec_add_folio(lruvec, folio); + __count_vm_events(UNEVICTABLE_PGCULLED, folio_nr_pages(folio)); +out: + folio_set_lru(folio); + return lruvec; +} + +static struct lruvec *__mlock_new_folio(struct folio *folio, struct lruvec *lruvec) +{ + VM_BUG_ON_FOLIO(folio_test_lru(folio), folio); + + lruvec = folio_lruvec_relock_irq(folio, lruvec); + + /* As above, this is a little surprising, but possible */ + if (unlikely(folio_evictable(folio))) + goto out; + + folio_set_unevictable(folio); + folio->mlock_count = !!folio_test_mlocked(folio); + __count_vm_events(UNEVICTABLE_PGCULLED, folio_nr_pages(folio)); +out: + lruvec_add_folio(lruvec, folio); + folio_set_lru(folio); + return lruvec; +} + +static struct lruvec *__munlock_folio(struct folio *folio, struct lruvec *lruvec) +{ + int nr_pages = folio_nr_pages(folio); + bool isolated = false; + + if (!folio_test_clear_lru(folio)) + goto munlock; + + isolated = true; + lruvec = folio_lruvec_relock_irq(folio, lruvec); + + if (folio_test_unevictable(folio)) { + /* Then mlock_count is maintained, but might undercount */ + if (folio->mlock_count) + folio->mlock_count--; + if (folio->mlock_count) + goto out; + } + /* else assume that was the last mlock: reclaim will fix it if not */ + +munlock: + if (folio_test_clear_mlocked(folio)) { + __zone_stat_mod_folio(folio, NR_MLOCK, -nr_pages); + if (isolated || !folio_test_unevictable(folio)) + __count_vm_events(UNEVICTABLE_PGMUNLOCKED, nr_pages); + else + __count_vm_events(UNEVICTABLE_PGSTRANDED, nr_pages); + } + + /* folio_evictable() has to be checked *after* clearing Mlocked */ + if (isolated && folio_test_unevictable(folio) && folio_evictable(folio)) { + lruvec_del_folio(lruvec, folio); + folio_clear_unevictable(folio); + lruvec_add_folio(lruvec, folio); + __count_vm_events(UNEVICTABLE_PGRESCUED, nr_pages); + } +out: + if (isolated) + folio_set_lru(folio); + return lruvec; +} + +/* + * Flags held in the low bits of a struct folio pointer on the mlock_fbatch. + */ +#define LRU_FOLIO 0x1 +#define NEW_FOLIO 0x2 +static inline struct folio *mlock_lru(struct folio *folio) +{ + return (struct folio *)((unsigned long)folio + LRU_FOLIO); +} + +static inline struct folio *mlock_new(struct folio *folio) +{ + return (struct folio *)((unsigned long)folio + NEW_FOLIO); +} + +/* + * mlock_folio_batch() is derived from folio_batch_move_lru(): perhaps that can + * make use of such folio pointer flags in future, but for now just keep it for + * mlock. We could use three separate folio batches instead, but one feels + * better (munlocking a full folio batch does not need to drain mlocking folio + * batches first). + */ +static void mlock_folio_batch(struct folio_batch *fbatch) +{ + struct lruvec *lruvec = NULL; + unsigned long mlock; + struct folio *folio; + int i; + + for (i = 0; i < folio_batch_count(fbatch); i++) { + folio = fbatch->folios[i]; + mlock = (unsigned long)folio & (LRU_FOLIO | NEW_FOLIO); + folio = (struct folio *)((unsigned long)folio - mlock); + fbatch->folios[i] = folio; + + if (mlock & LRU_FOLIO) + lruvec = __mlock_folio(folio, lruvec); + else if (mlock & NEW_FOLIO) + lruvec = __mlock_new_folio(folio, lruvec); + else + lruvec = __munlock_folio(folio, lruvec); + } + + if (lruvec) + unlock_page_lruvec_irq(lruvec); + folios_put(fbatch->folios, folio_batch_count(fbatch)); + folio_batch_reinit(fbatch); +} + +void mlock_drain_local(void) +{ + struct folio_batch *fbatch; + + local_lock(&mlock_fbatch.lock); + fbatch = this_cpu_ptr(&mlock_fbatch.fbatch); + if (folio_batch_count(fbatch)) + mlock_folio_batch(fbatch); + local_unlock(&mlock_fbatch.lock); +} + +void mlock_drain_remote(int cpu) +{ + struct folio_batch *fbatch; + + WARN_ON_ONCE(cpu_online(cpu)); + fbatch = &per_cpu(mlock_fbatch.fbatch, cpu); + if (folio_batch_count(fbatch)) + mlock_folio_batch(fbatch); +} + +bool need_mlock_drain(int cpu) +{ + return folio_batch_count(&per_cpu(mlock_fbatch.fbatch, cpu)); +} + +/** + * mlock_folio - mlock a folio already on (or temporarily off) LRU + * @folio: folio to be mlocked. + */ +void mlock_folio(struct folio *folio) +{ + struct folio_batch *fbatch; + + local_lock(&mlock_fbatch.lock); + fbatch = this_cpu_ptr(&mlock_fbatch.fbatch); + + if (!folio_test_set_mlocked(folio)) { + int nr_pages = folio_nr_pages(folio); + + zone_stat_mod_folio(folio, NR_MLOCK, nr_pages); + __count_vm_events(UNEVICTABLE_PGMLOCKED, nr_pages); + } + + folio_get(folio); + if (!folio_batch_add(fbatch, mlock_lru(folio)) || + folio_test_large(folio) || lru_cache_disabled()) + mlock_folio_batch(fbatch); + local_unlock(&mlock_fbatch.lock); +} + +/** + * mlock_new_folio - mlock a newly allocated folio not yet on LRU + * @folio: folio to be mlocked, either normal or a THP head. + */ +void mlock_new_folio(struct folio *folio) +{ + struct folio_batch *fbatch; + int nr_pages = folio_nr_pages(folio); + + local_lock(&mlock_fbatch.lock); + fbatch = this_cpu_ptr(&mlock_fbatch.fbatch); + folio_set_mlocked(folio); + + zone_stat_mod_folio(folio, NR_MLOCK, nr_pages); + __count_vm_events(UNEVICTABLE_PGMLOCKED, nr_pages); + + folio_get(folio); + if (!folio_batch_add(fbatch, mlock_new(folio)) || + folio_test_large(folio) || lru_cache_disabled()) + mlock_folio_batch(fbatch); + local_unlock(&mlock_fbatch.lock); +} + +/** + * munlock_folio - munlock a folio + * @folio: folio to be munlocked, either normal or a THP head. + */ +void munlock_folio(struct folio *folio) +{ + struct folio_batch *fbatch; + + local_lock(&mlock_fbatch.lock); + fbatch = this_cpu_ptr(&mlock_fbatch.fbatch); + /* + * folio_test_clear_mlocked(folio) must be left to __munlock_folio(), + * which will check whether the folio is multiply mlocked. + */ + folio_get(folio); + if (!folio_batch_add(fbatch, folio) || + folio_test_large(folio) || lru_cache_disabled()) + mlock_folio_batch(fbatch); + local_unlock(&mlock_fbatch.lock); +} + +static int mlock_pte_range(pmd_t *pmd, unsigned long addr, + unsigned long end, struct mm_walk *walk) + +{ + struct vm_area_struct *vma = walk->vma; + spinlock_t *ptl; + pte_t *start_pte, *pte; + pte_t ptent; + struct folio *folio; + + ptl = pmd_trans_huge_lock(pmd, vma); + if (ptl) { + if (!pmd_present(*pmd)) + goto out; + if (is_huge_zero_pmd(*pmd)) + goto out; + folio = page_folio(pmd_page(*pmd)); + if (vma->vm_flags & VM_LOCKED) + mlock_folio(folio); + else + munlock_folio(folio); + goto out; + } + + start_pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); + if (!start_pte) { + walk->action = ACTION_AGAIN; + return 0; + } + for (pte = start_pte; addr != end; pte++, addr += PAGE_SIZE) { + ptent = ptep_get(pte); + if (!pte_present(ptent)) + continue; + folio = vm_normal_folio(vma, addr, ptent); + if (!folio || folio_is_zone_device(folio)) + continue; + if (folio_test_large(folio)) + continue; + if (vma->vm_flags & VM_LOCKED) + mlock_folio(folio); + else + munlock_folio(folio); + } + pte_unmap(start_pte); +out: + spin_unlock(ptl); + cond_resched(); + return 0; +} + +/* + * mlock_vma_pages_range() - mlock any pages already in the range, + * or munlock all pages in the range. + * @vma - vma containing range to be mlock()ed or munlock()ed + * @start - start address in @vma of the range + * @end - end of range in @vma + * @newflags - the new set of flags for @vma. + * + * Called for mlock(), mlock2() and mlockall(), to set @vma VM_LOCKED; + * called for munlock() and munlockall(), to clear VM_LOCKED from @vma. + */ +static void mlock_vma_pages_range(struct vm_area_struct *vma, + unsigned long start, unsigned long end, vm_flags_t newflags) +{ + static const struct mm_walk_ops mlock_walk_ops = { + .pmd_entry = mlock_pte_range, + .walk_lock = PGWALK_WRLOCK_VERIFY, + }; + + /* + * There is a slight chance that concurrent page migration, + * or page reclaim finding a page of this now-VM_LOCKED vma, + * will call mlock_vma_folio() and raise page's mlock_count: + * double counting, leaving the page unevictable indefinitely. + * Communicate this danger to mlock_vma_folio() with VM_IO, + * which is a VM_SPECIAL flag not allowed on VM_LOCKED vmas. + * mmap_lock is held in write mode here, so this weird + * combination should not be visible to other mmap_lock users; + * but WRITE_ONCE so rmap walkers must see VM_IO if VM_LOCKED. + */ + if (newflags & VM_LOCKED) + newflags |= VM_IO; + vma_start_write(vma); + vm_flags_reset_once(vma, newflags); + + lru_add_drain(); + walk_page_range(vma->vm_mm, start, end, &mlock_walk_ops, NULL); + lru_add_drain(); + + if (newflags & VM_IO) { + newflags &= ~VM_IO; + vm_flags_reset_once(vma, newflags); + } +} + +/* + * mlock_fixup - handle mlock[all]/munlock[all] requests. + * + * Filters out "special" vmas -- VM_LOCKED never gets set for these, and + * munlock is a no-op. However, for some special vmas, we go ahead and + * populate the ptes. + * + * For vmas that pass the filters, merge/split as appropriate. + */ +static int mlock_fixup(struct vma_iterator *vmi, struct vm_area_struct *vma, + struct vm_area_struct **prev, unsigned long start, + unsigned long end, vm_flags_t newflags) +{ + struct mm_struct *mm = vma->vm_mm; + pgoff_t pgoff; + int nr_pages; + int ret = 0; + vm_flags_t oldflags = vma->vm_flags; + + if (newflags == oldflags || (oldflags & VM_SPECIAL) || + is_vm_hugetlb_page(vma) || vma == get_gate_vma(current->mm) || + vma_is_dax(vma) || vma_is_secretmem(vma)) + /* don't set VM_LOCKED or VM_LOCKONFAULT and don't count */ + goto out; + + pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT); + *prev = vma_merge(vmi, mm, *prev, start, end, newflags, + vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma), + vma->vm_userfaultfd_ctx, anon_vma_name(vma)); + if (*prev) { + vma = *prev; + goto success; + } + + if (start != vma->vm_start) { + ret = split_vma(vmi, vma, start, 1); + if (ret) + goto out; + } + + if (end != vma->vm_end) { + ret = split_vma(vmi, vma, end, 0); + if (ret) + goto out; + } + +success: + /* + * Keep track of amount of locked VM. + */ + nr_pages = (end - start) >> PAGE_SHIFT; + if (!(newflags & VM_LOCKED)) + nr_pages = -nr_pages; + else if (oldflags & VM_LOCKED) + nr_pages = 0; + mm->locked_vm += nr_pages; + + /* + * vm_flags is protected by the mmap_lock held in write mode. + * It's okay if try_to_unmap_one unmaps a page just after we + * set VM_LOCKED, populate_vma_page_range will bring it back. + */ + if ((newflags & VM_LOCKED) && (oldflags & VM_LOCKED)) { + /* No work to do, and mlocking twice would be wrong */ + vma_start_write(vma); + vm_flags_reset(vma, newflags); + } else { + mlock_vma_pages_range(vma, start, end, newflags); + } +out: + *prev = vma; + return ret; +} + +static int apply_vma_lock_flags(unsigned long start, size_t len, + vm_flags_t flags) +{ + unsigned long nstart, end, tmp; + struct vm_area_struct *vma, *prev; + VMA_ITERATOR(vmi, current->mm, start); + + VM_BUG_ON(offset_in_page(start)); + VM_BUG_ON(len != PAGE_ALIGN(len)); + end = start + len; + if (end < start) + return -EINVAL; + if (end == start) + return 0; + vma = vma_iter_load(&vmi); + if (!vma) + return -ENOMEM; + + prev = vma_prev(&vmi); + if (start > vma->vm_start) + prev = vma; + + nstart = start; + tmp = vma->vm_start; + for_each_vma_range(vmi, vma, end) { + int error; + vm_flags_t newflags; + + if (vma->vm_start != tmp) + return -ENOMEM; + + newflags = vma->vm_flags & ~VM_LOCKED_MASK; + newflags |= flags; + /* Here we know that vma->vm_start <= nstart < vma->vm_end. */ + tmp = vma->vm_end; + if (tmp > end) + tmp = end; + error = mlock_fixup(&vmi, vma, &prev, nstart, tmp, newflags); + if (error) + return error; + tmp = vma_iter_end(&vmi); + nstart = tmp; + } + + if (tmp < end) + return -ENOMEM; + + return 0; +} + +/* + * Go through vma areas and sum size of mlocked + * vma pages, as return value. + * Note deferred memory locking case(mlock2(,,MLOCK_ONFAULT) + * is also counted. + * Return value: previously mlocked page counts + */ +static unsigned long count_mm_mlocked_page_nr(struct mm_struct *mm, + unsigned long start, size_t len) +{ + struct vm_area_struct *vma; + unsigned long count = 0; + unsigned long end; + VMA_ITERATOR(vmi, mm, start); + + /* Don't overflow past ULONG_MAX */ + if (unlikely(ULONG_MAX - len < start)) + end = ULONG_MAX; + else + end = start + len; + + for_each_vma_range(vmi, vma, end) { + if (vma->vm_flags & VM_LOCKED) { + if (start > vma->vm_start) + count -= (start - vma->vm_start); + if (end < vma->vm_end) { + count += end - vma->vm_start; + break; + } + count += vma->vm_end - vma->vm_start; + } + } + + return count >> PAGE_SHIFT; +} + +/* + * convert get_user_pages() return value to posix mlock() error + */ +static int __mlock_posix_error_return(long retval) +{ + if (retval == -EFAULT) + retval = -ENOMEM; + else if (retval == -ENOMEM) + retval = -EAGAIN; + return retval; +} + +static __must_check int do_mlock(unsigned long start, size_t len, vm_flags_t flags) +{ + unsigned long locked; + unsigned long lock_limit; + int error = -ENOMEM; + + start = untagged_addr(start); + + if (!can_do_mlock()) + return -EPERM; + + len = PAGE_ALIGN(len + (offset_in_page(start))); + start &= PAGE_MASK; + + lock_limit = rlimit(RLIMIT_MEMLOCK); + lock_limit >>= PAGE_SHIFT; + locked = len >> PAGE_SHIFT; + + if (mmap_write_lock_killable(current->mm)) + return -EINTR; + + locked += current->mm->locked_vm; + if ((locked > lock_limit) && (!capable(CAP_IPC_LOCK))) { + /* + * It is possible that the regions requested intersect with + * previously mlocked areas, that part area in "mm->locked_vm" + * should not be counted to new mlock increment count. So check + * and adjust locked count if necessary. + */ + locked -= count_mm_mlocked_page_nr(current->mm, + start, len); + } + + /* check against resource limits */ + if ((locked <= lock_limit) || capable(CAP_IPC_LOCK)) + error = apply_vma_lock_flags(start, len, flags); + + mmap_write_unlock(current->mm); + if (error) + return error; + + error = __mm_populate(start, len, 0); + if (error) + return __mlock_posix_error_return(error); + return 0; +} + +SYSCALL_DEFINE2(mlock, unsigned long, start, size_t, len) +{ + return do_mlock(start, len, VM_LOCKED); +} + +SYSCALL_DEFINE3(mlock2, unsigned long, start, size_t, len, int, flags) +{ + vm_flags_t vm_flags = VM_LOCKED; + + if (flags & ~MLOCK_ONFAULT) + return -EINVAL; + + if (flags & MLOCK_ONFAULT) + vm_flags |= VM_LOCKONFAULT; + + return do_mlock(start, len, vm_flags); +} + +SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len) +{ + int ret; + + start = untagged_addr(start); + + len = PAGE_ALIGN(len + (offset_in_page(start))); + start &= PAGE_MASK; + + if (mmap_write_lock_killable(current->mm)) + return -EINTR; + ret = apply_vma_lock_flags(start, len, 0); + mmap_write_unlock(current->mm); + + return ret; +} + +/* + * Take the MCL_* flags passed into mlockall (or 0 if called from munlockall) + * and translate into the appropriate modifications to mm->def_flags and/or the + * flags for all current VMAs. + * + * There are a couple of subtleties with this. If mlockall() is called multiple + * times with different flags, the values do not necessarily stack. If mlockall + * is called once including the MCL_FUTURE flag and then a second time without + * it, VM_LOCKED and VM_LOCKONFAULT will be cleared from mm->def_flags. + */ +static int apply_mlockall_flags(int flags) +{ + VMA_ITERATOR(vmi, current->mm, 0); + struct vm_area_struct *vma, *prev = NULL; + vm_flags_t to_add = 0; + + current->mm->def_flags &= ~VM_LOCKED_MASK; + if (flags & MCL_FUTURE) { + current->mm->def_flags |= VM_LOCKED; + + if (flags & MCL_ONFAULT) + current->mm->def_flags |= VM_LOCKONFAULT; + + if (!(flags & MCL_CURRENT)) + goto out; + } + + if (flags & MCL_CURRENT) { + to_add |= VM_LOCKED; + if (flags & MCL_ONFAULT) + to_add |= VM_LOCKONFAULT; + } + + for_each_vma(vmi, vma) { + vm_flags_t newflags; + + newflags = vma->vm_flags & ~VM_LOCKED_MASK; + newflags |= to_add; + + /* Ignore errors */ + mlock_fixup(&vmi, vma, &prev, vma->vm_start, vma->vm_end, + newflags); + cond_resched(); + } +out: + return 0; +} + +SYSCALL_DEFINE1(mlockall, int, flags) +{ + unsigned long lock_limit; + int ret; + + if (!flags || (flags & ~(MCL_CURRENT | MCL_FUTURE | MCL_ONFAULT)) || + flags == MCL_ONFAULT) + return -EINVAL; + + if (!can_do_mlock()) + return -EPERM; + + lock_limit = rlimit(RLIMIT_MEMLOCK); + lock_limit >>= PAGE_SHIFT; + + if (mmap_write_lock_killable(current->mm)) + return -EINTR; + + ret = -ENOMEM; + if (!(flags & MCL_CURRENT) || (current->mm->total_vm <= lock_limit) || + capable(CAP_IPC_LOCK)) + ret = apply_mlockall_flags(flags); + mmap_write_unlock(current->mm); + if (!ret && (flags & MCL_CURRENT)) + mm_populate(0, TASK_SIZE); + + return ret; +} + +SYSCALL_DEFINE0(munlockall) +{ + int ret; + + if (mmap_write_lock_killable(current->mm)) + return -EINTR; + ret = apply_mlockall_flags(0); + mmap_write_unlock(current->mm); + return ret; +} + +/* + * Objects with different lifetime than processes (SHM_LOCK and SHM_HUGETLB + * shm segments) get accounted against the user_struct instead. + */ +static DEFINE_SPINLOCK(shmlock_user_lock); + +int user_shm_lock(size_t size, struct ucounts *ucounts) +{ + unsigned long lock_limit, locked; + long memlock; + int allowed = 0; + + locked = (size + PAGE_SIZE - 1) >> PAGE_SHIFT; + lock_limit = rlimit(RLIMIT_MEMLOCK); + if (lock_limit != RLIM_INFINITY) + lock_limit >>= PAGE_SHIFT; + spin_lock(&shmlock_user_lock); + memlock = inc_rlimit_ucounts(ucounts, UCOUNT_RLIMIT_MEMLOCK, locked); + + if ((memlock == LONG_MAX || memlock > lock_limit) && !capable(CAP_IPC_LOCK)) { + dec_rlimit_ucounts(ucounts, UCOUNT_RLIMIT_MEMLOCK, locked); + goto out; + } + if (!get_ucounts(ucounts)) { + dec_rlimit_ucounts(ucounts, UCOUNT_RLIMIT_MEMLOCK, locked); + allowed = 0; + goto out; + } + allowed = 1; +out: + spin_unlock(&shmlock_user_lock); + return allowed; +} + +void user_shm_unlock(size_t size, struct ucounts *ucounts) +{ + spin_lock(&shmlock_user_lock); + dec_rlimit_ucounts(ucounts, UCOUNT_RLIMIT_MEMLOCK, (size + PAGE_SIZE - 1) >> PAGE_SHIFT); + spin_unlock(&shmlock_user_lock); + put_ucounts(ucounts); +} |