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Subject[PATCH] v9fs: handle async processing of F_SETLK with FL_SLEEP flag
Date
kernel export thread (nfsd/lockd/ksmbd) uses F_SETLK cmd with the FL_SLEEP
flag set to request asynchronous processing of blocking locks.

Currently v9fs does not support such requests and calls blocking
locks_lock_file_wait() function.

To work around the problem let's detect such request, drop FL_SLEEP
before execution of potentially blocking functions.

Dropped FL_SLEEP flag should be restored back because some calling
function (nfsd4_lock) require it.

https://bugzilla.kernel.org/show_bug.cgi?id=215383
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
---
fs/9p/vfs_file.c | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/fs/9p/vfs_file.c b/fs/9p/vfs_file.c
index 612e297f3763..81c98afdbb32 100644
--- a/fs/9p/vfs_file.c
+++ b/fs/9p/vfs_file.c
@@ -135,6 +135,7 @@ static int v9fs_file_do_lock(struct file *filp, int cmd, struct file_lock *fl)
int res = 0;
unsigned char fl_type;
struct v9fs_session_info *v9ses;
+ bool async = false;

fid = filp->private_data;
BUG_ON(fid == NULL);
@@ -142,6 +143,10 @@ static int v9fs_file_do_lock(struct file *filp, int cmd, struct file_lock *fl)
if ((fl->fl_flags & FL_POSIX) != FL_POSIX)
BUG();

+ async = (fl->fl_flags & FL_SLEEP) && IS_SETLK(cmd);
+ if (async)
+ fl->fl_flags &= ~FL_SLEEP;
+
res = locks_lock_file_wait(filp, fl);
if (res < 0)
goto out;
@@ -230,6 +235,8 @@ static int v9fs_file_do_lock(struct file *filp, int cmd, struct file_lock *fl)
if (flock.client_id != fid->clnt->name)
kfree(flock.client_id);
out:
+ if (async)
+ fl->fl_flags |= FL_SLEEP;
return res;
}

--
2.25.1
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