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From: Dominique Martinet <[email protected]>
To: Dan Carpenter <[email protected]>
Cc: [email protected],
	Alexander Viro <[email protected]>,
	Christian Brauner <[email protected]>,
	Jens Axboe <[email protected]>,
	Pavel Begunkov <[email protected]>,
	Stefan Roesch <[email protected]>,
	[email protected], [email protected],
	Clay Harris <[email protected]>,
	Dave Chinner <[email protected]>,
	[email protected], [email protected],
	[email protected]
Subject: Re: [PATCH v2 4/6] kernfs: implement readdir FMODE_NOWAIT
Date: Thu, 11 May 2023 20:03:12 +0900	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

Dan Carpenter wrote on Thu, May 11, 2023 at 01:55:57PM +0300:
> fd7b9f7b9776b1 Tejun Heo          2013-11-28  1850  		if (!dir_emit(ctx, name, len, ino, type))
> fd7b9f7b9776b1 Tejun Heo          2013-11-28  1851  			return 0;
> 393c3714081a53 Minchan Kim        2021-11-18  1852  		down_read(&root->kernfs_rwsem);
>                                                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> Needs to be deleted.

Uh, yes, sorry; I'm not sure how I let that slip, I guess I didn't hit
any dead lock because nothing ever tried to take a write lock after
getdents...
Thanks!

I expect there'll be other comments (this might not make it at all), so
I'll keep the v3 of this patch with this fix locally and resend after
other comments.

> a551138c4b3b9f Dominique Martinet 2023-05-10  1853  		if (ctx->flags & DIR_CONTEXT_F_NOWAIT) {
> a551138c4b3b9f Dominique Martinet 2023-05-10  1854  			if (!down_read_trylock(&root->kernfs_rwsem))
> a551138c4b3b9f Dominique Martinet 2023-05-10  1855  				return 0;
> 
> It's a bit strange the this doesn't return -EAGAIN;

That is on purpose: the getdents did work (dir_emit returned success at
least once), so the caller can process whatever was filled in the buffer
before calling iterate_shared() again.

If we were to return -EAGAIN here, we'd actually be throwing out the
entries we just filled in, and that's not what we want.

-- 
Dominique Martinet | Asmadeus

  reply	other threads:[~2023-05-11 11:03 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-05-10 10:52 [PATCH v2 0/6] io_uring: add getdents support, take 2 Dominique Martinet
2023-05-10 10:52 ` [PATCH v2 1/6] fs: split off vfs_getdents function of getdents64 syscall Dominique Martinet
2023-05-23 15:39   ` Christian Brauner
2023-05-23 21:13     ` Dominique Martinet
2023-05-10 10:52 ` [PATCH v2 2/6] vfs_getdents/struct dir_context: add flags field Dominique Martinet
2023-05-10 10:52 ` [PATCH v2 3/6] io_uring: add support for getdents Dominique Martinet
2023-05-10 10:52 ` [PATCH v2 4/6] kernfs: implement readdir FMODE_NOWAIT Dominique Martinet
2023-05-11 10:55   ` Dan Carpenter
2023-05-11 11:03     ` Dominique Martinet [this message]
2023-05-10 10:52 ` [PATCH v2 5/6] libfs: set FMODE_NOWAIT on dir open Dominique Martinet
2023-05-10 10:52 ` [PATCH v2 6/6] RFC: io_uring getdents: test returning an EOF flag in CQE Dominique Martinet
2023-05-23 14:30   ` Christian Brauner
2023-05-23 21:05     ` Dominique Martinet
2023-05-24 13:52       ` [PATCH v2 1/6] fs: split off vfs_getdents function of getdents64 syscall Christian Brauner
2023-05-24 21:36         ` Dominique Martinet
2023-05-25  9:22           ` Christian Brauner
2023-05-25 11:00             ` Dominique Martinet
2023-05-25 12:33               ` Christian Brauner
2023-07-11  8:17               ` Hao Xu
2023-07-11  8:24                 ` Dominique Martinet

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