mirror of
https://mirrors.bfsu.edu.cn/git/linux.git
synced 2024-09-21 12:11:49 +08:00
vfs: dodge smp_mb in break_lease and break_deleg in the common case
These inlines show up in the fast path (e.g., in do_dentry_open()) and induce said full barrier regarding i_flctx access when in most cases the pointer is NULL. The pointer can be safely checked before issuing the barrier, dodging it in most cases as a result. It is plausible the consume fence would be sufficient, but I don't want to go audit all callers regarding what they before calling here. Signed-off-by: Mateusz Guzik <mjguzik@gmail.com> Link: https://lore.kernel.org/r/20240806172846.886570-1-mjguzik@gmail.com Reviewed-by: Jeff Layton <jlayton@kernel.org> Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
parent
215ab0d8af
commit
087adb4f0f
@ -420,28 +420,38 @@ static inline int locks_lock_file_wait(struct file *filp, struct file_lock *fl)
|
||||
#ifdef CONFIG_FILE_LOCKING
|
||||
static inline int break_lease(struct inode *inode, unsigned int mode)
|
||||
{
|
||||
struct file_lock_context *flctx;
|
||||
|
||||
/*
|
||||
* Since this check is lockless, we must ensure that any refcounts
|
||||
* taken are done before checking i_flctx->flc_lease. Otherwise, we
|
||||
* could end up racing with tasks trying to set a new lease on this
|
||||
* file.
|
||||
*/
|
||||
flctx = READ_ONCE(inode->i_flctx);
|
||||
if (!flctx)
|
||||
return 0;
|
||||
smp_mb();
|
||||
if (inode->i_flctx && !list_empty_careful(&inode->i_flctx->flc_lease))
|
||||
if (!list_empty_careful(&flctx->flc_lease))
|
||||
return __break_lease(inode, mode, FL_LEASE);
|
||||
return 0;
|
||||
}
|
||||
|
||||
static inline int break_deleg(struct inode *inode, unsigned int mode)
|
||||
{
|
||||
struct file_lock_context *flctx;
|
||||
|
||||
/*
|
||||
* Since this check is lockless, we must ensure that any refcounts
|
||||
* taken are done before checking i_flctx->flc_lease. Otherwise, we
|
||||
* could end up racing with tasks trying to set a new lease on this
|
||||
* file.
|
||||
*/
|
||||
flctx = READ_ONCE(inode->i_flctx);
|
||||
if (!flctx)
|
||||
return 0;
|
||||
smp_mb();
|
||||
if (inode->i_flctx && !list_empty_careful(&inode->i_flctx->flc_lease))
|
||||
if (!list_empty_careful(&flctx->flc_lease))
|
||||
return __break_lease(inode, mode, FL_DELEG);
|
||||
return 0;
|
||||
}
|
||||
|
Loading…
Reference in New Issue
Block a user