fs/locks: Replace lg_global with a percpu-rwsem
Replace the global part of the lglock with a percpu-rwsem. Since fcl_lock is a spinlock and itself nests under i_lock, which too is a spinlock we cannot acquire sleeping locks at locks_{insert,remove}_global_locks(). We can however wrap all fcl_lock acquisitions with percpu_down_read such that all invocations of locks_{insert,remove}_global_locks() have that read lock held. This allows us to replace the lg_global part of the lglock with the write side of the rwsem. In the absense of writers, percpu_{down,up}_read() are free of atomic instructions. This further avoids the very long preempt-disable regions caused by lglock on larger machines. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Al Viro <viro@ZenIV.linux.org.uk> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: dave@stgolabs.net Cc: der.herr@hofr.at Cc: paulmck@linux.vnet.ibm.com Cc: riel@redhat.com Cc: tj@kernel.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Родитель
11d9684ca6
Коммит
aba3766073
21
fs/locks.c
21
fs/locks.c
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@ -164,6 +164,7 @@ int lease_break_time = 45;
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*/
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*/
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DEFINE_STATIC_LGLOCK(file_lock_lglock);
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DEFINE_STATIC_LGLOCK(file_lock_lglock);
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static DEFINE_PER_CPU(struct hlist_head, file_lock_list);
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static DEFINE_PER_CPU(struct hlist_head, file_lock_list);
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DEFINE_STATIC_PERCPU_RWSEM(file_rwsem);
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/*
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/*
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* The blocked_hash is used to find POSIX lock loops for deadlock detection.
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* The blocked_hash is used to find POSIX lock loops for deadlock detection.
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@ -587,6 +588,8 @@ static int posix_same_owner(struct file_lock *fl1, struct file_lock *fl2)
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/* Must be called with the flc_lock held! */
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/* Must be called with the flc_lock held! */
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static void locks_insert_global_locks(struct file_lock *fl)
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static void locks_insert_global_locks(struct file_lock *fl)
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{
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{
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percpu_rwsem_assert_held(&file_rwsem);
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lg_local_lock(&file_lock_lglock);
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lg_local_lock(&file_lock_lglock);
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fl->fl_link_cpu = smp_processor_id();
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fl->fl_link_cpu = smp_processor_id();
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hlist_add_head(&fl->fl_link, this_cpu_ptr(&file_lock_list));
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hlist_add_head(&fl->fl_link, this_cpu_ptr(&file_lock_list));
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@ -596,6 +599,8 @@ static void locks_insert_global_locks(struct file_lock *fl)
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/* Must be called with the flc_lock held! */
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/* Must be called with the flc_lock held! */
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static void locks_delete_global_locks(struct file_lock *fl)
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static void locks_delete_global_locks(struct file_lock *fl)
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{
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{
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percpu_rwsem_assert_held(&file_rwsem);
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/*
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/*
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* Avoid taking lock if already unhashed. This is safe since this check
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* Avoid taking lock if already unhashed. This is safe since this check
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* is done while holding the flc_lock, and new insertions into the list
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* is done while holding the flc_lock, and new insertions into the list
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@ -915,6 +920,7 @@ static int flock_lock_inode(struct inode *inode, struct file_lock *request)
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return -ENOMEM;
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return -ENOMEM;
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}
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}
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percpu_down_read(&file_rwsem);
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spin_lock(&ctx->flc_lock);
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spin_lock(&ctx->flc_lock);
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if (request->fl_flags & FL_ACCESS)
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if (request->fl_flags & FL_ACCESS)
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goto find_conflict;
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goto find_conflict;
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@ -955,6 +961,7 @@ find_conflict:
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out:
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out:
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spin_unlock(&ctx->flc_lock);
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spin_unlock(&ctx->flc_lock);
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percpu_up_read(&file_rwsem);
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if (new_fl)
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if (new_fl)
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locks_free_lock(new_fl);
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locks_free_lock(new_fl);
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locks_dispose_list(&dispose);
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locks_dispose_list(&dispose);
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@ -991,6 +998,7 @@ static int posix_lock_inode(struct inode *inode, struct file_lock *request,
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new_fl2 = locks_alloc_lock();
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new_fl2 = locks_alloc_lock();
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}
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}
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percpu_down_read(&file_rwsem);
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spin_lock(&ctx->flc_lock);
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spin_lock(&ctx->flc_lock);
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/*
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/*
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* New lock request. Walk all POSIX locks and look for conflicts. If
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* New lock request. Walk all POSIX locks and look for conflicts. If
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@ -1162,6 +1170,7 @@ static int posix_lock_inode(struct inode *inode, struct file_lock *request,
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}
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}
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out:
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out:
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spin_unlock(&ctx->flc_lock);
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spin_unlock(&ctx->flc_lock);
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percpu_up_read(&file_rwsem);
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/*
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/*
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* Free any unused locks.
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* Free any unused locks.
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*/
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*/
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@ -1436,6 +1445,7 @@ int __break_lease(struct inode *inode, unsigned int mode, unsigned int type)
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return error;
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return error;
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}
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}
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percpu_down_read(&file_rwsem);
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spin_lock(&ctx->flc_lock);
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spin_lock(&ctx->flc_lock);
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time_out_leases(inode, &dispose);
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time_out_leases(inode, &dispose);
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@ -1487,9 +1497,13 @@ restart:
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locks_insert_block(fl, new_fl);
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locks_insert_block(fl, new_fl);
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trace_break_lease_block(inode, new_fl);
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trace_break_lease_block(inode, new_fl);
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spin_unlock(&ctx->flc_lock);
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spin_unlock(&ctx->flc_lock);
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percpu_up_read(&file_rwsem);
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locks_dispose_list(&dispose);
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locks_dispose_list(&dispose);
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error = wait_event_interruptible_timeout(new_fl->fl_wait,
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error = wait_event_interruptible_timeout(new_fl->fl_wait,
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!new_fl->fl_next, break_time);
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!new_fl->fl_next, break_time);
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percpu_down_read(&file_rwsem);
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spin_lock(&ctx->flc_lock);
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spin_lock(&ctx->flc_lock);
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trace_break_lease_unblock(inode, new_fl);
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trace_break_lease_unblock(inode, new_fl);
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locks_delete_block(new_fl);
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locks_delete_block(new_fl);
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@ -1506,6 +1520,7 @@ restart:
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}
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}
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out:
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out:
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spin_unlock(&ctx->flc_lock);
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spin_unlock(&ctx->flc_lock);
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percpu_up_read(&file_rwsem);
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locks_dispose_list(&dispose);
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locks_dispose_list(&dispose);
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locks_free_lock(new_fl);
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locks_free_lock(new_fl);
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return error;
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return error;
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@ -1660,6 +1675,7 @@ generic_add_lease(struct file *filp, long arg, struct file_lock **flp, void **pr
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return -EINVAL;
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return -EINVAL;
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}
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}
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percpu_down_read(&file_rwsem);
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spin_lock(&ctx->flc_lock);
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spin_lock(&ctx->flc_lock);
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time_out_leases(inode, &dispose);
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time_out_leases(inode, &dispose);
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error = check_conflicting_open(dentry, arg, lease->fl_flags);
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error = check_conflicting_open(dentry, arg, lease->fl_flags);
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@ -1730,6 +1746,7 @@ out_setup:
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lease->fl_lmops->lm_setup(lease, priv);
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lease->fl_lmops->lm_setup(lease, priv);
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out:
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out:
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spin_unlock(&ctx->flc_lock);
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spin_unlock(&ctx->flc_lock);
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percpu_up_read(&file_rwsem);
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locks_dispose_list(&dispose);
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locks_dispose_list(&dispose);
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if (is_deleg)
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if (is_deleg)
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inode_unlock(inode);
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inode_unlock(inode);
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@ -1752,6 +1769,7 @@ static int generic_delete_lease(struct file *filp, void *owner)
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return error;
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return error;
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}
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}
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percpu_down_read(&file_rwsem);
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spin_lock(&ctx->flc_lock);
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spin_lock(&ctx->flc_lock);
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list_for_each_entry(fl, &ctx->flc_lease, fl_list) {
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list_for_each_entry(fl, &ctx->flc_lease, fl_list) {
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if (fl->fl_file == filp &&
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if (fl->fl_file == filp &&
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@ -1764,6 +1782,7 @@ static int generic_delete_lease(struct file *filp, void *owner)
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if (victim)
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if (victim)
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error = fl->fl_lmops->lm_change(victim, F_UNLCK, &dispose);
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error = fl->fl_lmops->lm_change(victim, F_UNLCK, &dispose);
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spin_unlock(&ctx->flc_lock);
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spin_unlock(&ctx->flc_lock);
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percpu_up_read(&file_rwsem);
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locks_dispose_list(&dispose);
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locks_dispose_list(&dispose);
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return error;
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return error;
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}
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}
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@ -2703,6 +2722,7 @@ static void *locks_start(struct seq_file *f, loff_t *pos)
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struct locks_iterator *iter = f->private;
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struct locks_iterator *iter = f->private;
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iter->li_pos = *pos + 1;
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iter->li_pos = *pos + 1;
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percpu_down_write(&file_rwsem);
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lg_global_lock(&file_lock_lglock);
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lg_global_lock(&file_lock_lglock);
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spin_lock(&blocked_lock_lock);
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spin_lock(&blocked_lock_lock);
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return seq_hlist_start_percpu(&file_lock_list, &iter->li_cpu, *pos);
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return seq_hlist_start_percpu(&file_lock_list, &iter->li_cpu, *pos);
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@ -2721,6 +2741,7 @@ static void locks_stop(struct seq_file *f, void *v)
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{
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{
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spin_unlock(&blocked_lock_lock);
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spin_unlock(&blocked_lock_lock);
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lg_global_unlock(&file_lock_lglock);
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lg_global_unlock(&file_lock_lglock);
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percpu_up_write(&file_rwsem);
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}
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}
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static const struct seq_operations locks_seq_operations = {
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static const struct seq_operations locks_seq_operations = {
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