merged into cifs-2.6.git for-next
thx
On Tue, May 9, 2017 at 8:34 PM, Pavel Shilovsky <pshilovsky@xxxxxxxxx> wrote:
> 2017-05-03 8:17 GMT-07:00 Rabin Vincent <rabin.vincent@xxxxxxxx>:
>> From: Rabin Vincent <rabinv@xxxxxxxx>
>>
>> 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@xxxxxxxx>
>> ---
>> fs/cifs/file.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/fs/cifs/file.c b/fs/cifs/file.c
>> index 21d4045..64b590b 100644
>> --- a/fs/cifs/file.c
>> +++ b/fs/cifs/file.c
>> @@ -582,7 +582,7 @@ cifs_relock_file(struct cifsFileInfo *cfile)
>> 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);
>> --
>> 2.1.4
>>
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>
> Acked-by: Pavel Shilovsky <pshilov@xxxxxxxxxxxxx>
>
> Best regards,
> Pavel Shilovsky
> --
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--
Thanks,
Steve
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