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lockd: don't call vfs_lock_file() for pending requests

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This patch returns nlm_lck_blocked in nlmsvc_lock() when an asynchronous
lock request is pending. During testing I ran into the case with the
side-effects that lockd is waiting for only one lm_grant() callback
because it's already part of the nlm_blocked list. If another
asynchronous for the same nlm_block is triggered two lm_grant()
callbacks will occur but lockd was only waiting for one.

To avoid any change of existing users this handling will only being made
when export_op_support_safe_async_lock() returns true.

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Alexander Aring <aahringo@redhat.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
This commit is contained in:
Alexander Aring 2023-09-12 17:53:19 -04:00 committed by Chuck Lever
parent 2dd10de8e6
commit b743612c0a
1 changed files with 16 additions and 7 deletions
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23
fs/lockd/svclock.c
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@ -541,6 +541,22 @@ nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file,
goto out;
}
spin_lock(&nlm_blocked_lock);
/*
* If this is a lock request for an already pending
* lock request we return nlm_lck_blocked without calling
* vfs_lock_file() again. Otherwise we have two pending
* requests on the underlaying ->lock() implementation but
* only one nlm_block to being granted by lm_grant().
*/
if (exportfs_lock_op_is_async(inode->i_sb->s_export_op) &&
!list_empty(&block->b_list)) {
spin_unlock(&nlm_blocked_lock);
ret = nlm_lck_blocked;
goto out;
}
spin_unlock(&nlm_blocked_lock);
if (!wait)
lock->fl.fl_flags &= ~FL_SLEEP;
mode = lock_to_openmode(&lock->fl);
@ -553,13 +569,6 @@ nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file,
ret = nlm_granted;
goto out;
case -EAGAIN:
/*
* If this is a blocking request for an
* already pending lock request then we need
* to put it back on lockd's block list
*/
if (wait)
break;
ret = async_block ? nlm_lck_blocked : nlm_lck_denied;
goto out;
case FILE_LOCK_DEFERRED: