Allow locks_mandatory_area() to handle file-private locks correctly.
If there is a file-private lock set on an open file and we're doing I/O
via the same, then that should not cause anything to block.
Handle this by first doing a non-blocking FL_ACCESS check for a
file-private lock, and then fall back to checking for a classic POSIX
lock (and possibly blocking).
Note that this approach is subject to the same races that have always
plagued mandatory locking on Linux.
Reported-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
---
fs/locks.c | 15 +++++++++++++--
1 file changed, 13 insertions(+), 2 deletions(-)
diff --git a/fs/locks.c b/fs/locks.c
index b2b3e97b64d4..ad37b3eb185d 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -1199,19 +1199,30 @@ int locks_mandatory_area(int read_write, struct inode *inode,
{
struct file_lock fl;
int error;
+ bool sleep = false;
locks_init_lock(&fl);
- fl.fl_owner = current->files;
fl.fl_pid = current->tgid;
fl.fl_file = filp;
fl.fl_flags = FL_POSIX | FL_ACCESS;
if (filp && !(filp->f_flags & O_NONBLOCK))
- fl.fl_flags |= FL_SLEEP;
+ sleep = true;
fl.fl_type = (read_write == FLOCK_VERIFY_WRITE) ? F_WRLCK : F_RDLCK;
fl.fl_start = offset;
fl.fl_end = offset + count - 1;
for (;;) {
+ if (filp) {
+ fl.fl_owner = (fl_owner_t)filp;
+ fl.fl_flags &= ~FL_SLEEP;
+ error = __posix_lock_file(inode, &fl, NULL);
+ if (!error)
+ break;
+ }
+
+ if (sleep)
+ fl.fl_flags |= FL_SLEEP;
+ fl.fl_owner = current->files;
error = __posix_lock_file(inode, &fl, NULL);
if (error != FILE_LOCK_DEFERRED)
break;
--
1.8.5.3
--
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