linux-ext4 - Re: [PATCH 2/7] xfs: add nowait support for xfs_seek_iomap

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Date:   Thu, 27 Jul 2023 20:17:52 +0800
From:   Hao Xu <hao.xu@...ux.dev>
To:     "Darrick J. Wong" <djwong@...nel.org>,
        Dave Chinner <david@...morbit.com>
Cc:     io-uring@...r.kernel.org, Jens Axboe <axboe@...nel.dk>,
        Dominique Martinet <asmadeus@...ewreck.org>,
        Pavel Begunkov <asml.silence@...il.com>,
        Christian Brauner <brauner@...nel.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Stefan Roesch <shr@...com>, Clay Harris <bugs@...ycon.org>,
        linux-fsdevel@...r.kernel.org, linux-xfs@...r.kernel.org,
        linux-ext4@...r.kernel.org, Wanpeng Li <wanpengli@...cent.com>
Subject: Re: [PATCH 2/7] xfs: add nowait support for xfs_seek_iomap_begin()

On 7/27/23 06:14, Darrick J. Wong wrote:
> On Thu, Jul 27, 2023 at 07:55:47AM +1000, Dave Chinner wrote:
>> On Wed, Jul 26, 2023 at 06:25:58PM +0800, Hao Xu wrote:
>>> From: Hao Xu <howeyxu@...cent.com>
>>>
>>> To support nowait llseek(), IOMAP_NOWAIT semantics should be respected.
>>> In xfs, xfs_seek_iomap_begin() is the only place which may be blocked
>>> by ilock and extent loading. Let's turn it into trylock logic just like
>>> what we've done in xfs_readdir().
>>>
>>> Signed-off-by: Hao Xu <howeyxu@...cent.com>
>>> ---
>>>   fs/xfs/xfs_iomap.c | 4 +++-
>>>   1 file changed, 3 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
>>> index 18c8f168b153..bbd7c6b27701 100644
>>> --- a/fs/xfs/xfs_iomap.c
>>> +++ b/fs/xfs/xfs_iomap.c
>>> @@ -1294,7 +1294,9 @@ xfs_seek_iomap_begin(
>>>   	if (xfs_is_shutdown(mp))
>>>   		return -EIO;
>>>   
>>> -	lockmode = xfs_ilock_data_map_shared(ip);
>>> +	lockmode = xfs_ilock_data_map_shared_generic(ip, flags & IOMAP_NOWAIT);
>>
>> What does this magic XFS function I can't find anywhere in this
>> patch set do?

Sorry, forgot to say, It was xfs_ilock_for_readdir() in io_uring
getdents patchset, I changed the name since it is now used for
lseek as well.

> 
> It's in (iirc) the io_uring getdents patchset that wasn't cc'd to
> linux-xfs and that I haven't looked at yet.
> 

Hi Darrick, I forwarded the xfs related patch in that series. Forgot to
cc xfs list at the beginning. I'll make xfs list be Cc-ed when sending
next version. Sorry for inconvenience.

Regards,
Hao

> --D
> 
>> -Dave.
>> -- 
>> Dave Chinner
>> david@...morbit.com