Re: [GIT PULL] io_uring dma-buf support for 7.4

[Jens Axboe <axboe@kernel.dk>]

On 10/27/26 11:45 AM, Linus Torvalds wrote:
> On Sun, 25 Oct 2026 at 03:30, Jens Axboe <axboe@kernel.dk> wrote:
>>
>> This adds native dma-buf support to the I/O path
> 
> So while doing the trivial resolution, and looking at the code, I note
> that blkdev_buffered_write() grew a
> 
>     inode_lock_shared
>     ..
>     inode_unlock_shared
> 
> in it. But looking at the two call sites (in blkdev_write_iter()),
> _one_ of them already has that inode_lock_shared() on what seems to be
> the exact same inode (bdev_file_inode(iocb->ki_filp))
> 
> These all went through you in the original block pull:
> 
>   1b1be9ea4e34 block: take the inode lock for buffered write fallback
>   2fec4fd97cc3 block: take i_rwsem for the direct I/O write fallback
> 
> am I missing something? That nested locking looks not just
> unnecessary, it looks like deadlock city. I'm surprised lockdep hasn't
> complained, but I'm assuming hardly anybody actually uses this path.

Someone did actually report it recently, after it had been in
for-next for a long time. There is a fix queued up for it:

https://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux.git/commit/?h=block-7.4&id=21b88cc8bafceee6c6c82503e3b2cc6f1d0c78bf

since this morning! It'll go out later this week, pre -rc1.

-- 
Jens Axboe