4.4-stable review patch. If anyone has any objections, please let me know.
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From: Rabin Vincent rabinv@axis.com
[ Upstream commit 560d388950ceda5e7c7cdef7f3d9a8ff297bbf9d ]
cifs_relock_file() can perform a down_write() on the inode's lock_sem even though it was already performed in cifs_strict_readv(). Lockdep complains about this. AFAICS, there is no problem here, and lockdep just needs to be told that this nesting is OK.
============================================= [ INFO: possible recursive locking detected ] 4.11.0+ #20 Not tainted --------------------------------------------- cat/701 is trying to acquire lock: (&cifsi->lock_sem){++++.+}, at: cifs_reopen_file+0x7a7/0xc00
but task is already holding lock: (&cifsi->lock_sem){++++.+}, at: cifs_strict_readv+0x177/0x310
other info that might help us debug this: Possible unsafe locking scenario:
CPU0 ---- lock(&cifsi->lock_sem); lock(&cifsi->lock_sem);
*** DEADLOCK ***
May be due to missing lock nesting notation
1 lock held by cat/701: #0: (&cifsi->lock_sem){++++.+}, at: cifs_strict_readv+0x177/0x310
stack backtrace: CPU: 0 PID: 701 Comm: cat Not tainted 4.11.0+ #20 Call Trace: dump_stack+0x85/0xc2 __lock_acquire+0x17dd/0x2260 ? trace_hardirqs_on_thunk+0x1a/0x1c ? preempt_schedule_irq+0x6b/0x80 lock_acquire+0xcc/0x260 ? lock_acquire+0xcc/0x260 ? cifs_reopen_file+0x7a7/0xc00 down_read+0x2d/0x70 ? cifs_reopen_file+0x7a7/0xc00 cifs_reopen_file+0x7a7/0xc00 ? printk+0x43/0x4b cifs_readpage_worker+0x327/0x8a0 cifs_readpage+0x8c/0x2a0 generic_file_read_iter+0x692/0xd00 cifs_strict_readv+0x29f/0x310 generic_file_splice_read+0x11c/0x1c0 do_splice_to+0xa5/0xc0 splice_direct_to_actor+0xfa/0x350 ? generic_pipe_buf_nosteal+0x10/0x10 do_splice_direct+0xb5/0xe0 do_sendfile+0x278/0x3a0 SyS_sendfile64+0xc4/0xe0 entry_SYSCALL_64_fastpath+0x1f/0xbe
Signed-off-by: Rabin Vincent rabinv@axis.com Acked-by: Pavel Shilovsky pshilov@microsoft.com Signed-off-by: Steve French smfrench@gmail.com Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/cifs/file.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/fs/cifs/file.c +++ b/fs/cifs/file.c @@ -589,7 +589,7 @@ cifs_relock_file(struct cifsFileInfo *cf struct cifs_tcon *tcon = tlink_tcon(cfile->tlink); int rc = 0;
- down_read(&cinode->lock_sem); + down_read_nested(&cinode->lock_sem, SINGLE_DEPTH_NESTING); if (cinode->can_cache_brlcks) { /* can cache locks - no need to relock */ up_read(&cinode->lock_sem);