From 29723adee11804b548903ddb1db666cf4a60f60e Mon Sep 17 00:00:00 2001 From: Jeff Layton Date: Mon, 10 Mar 2014 09:54:19 -0400 Subject: locks: make locks_mandatory_area check for file-private locks 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 Signed-off-by: Jeff Layton --- fs/locks.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/fs/locks.c b/fs/locks.c index d82c51c4fcd2..13fc7a6d380a 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; -- cgit v1.2.3