From: "Darrick J. Wong" <djwong@kernel.org>
To: Andrey Albershteyn <aalbersh@redhat.com>
Cc: Eric Biggers <ebiggers@kernel.org>,
linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
fsverity@lists.linux.dev
Subject: Re: [PATCH 12/13] fsverity: remove system-wide workqueue
Date: Mon, 29 Apr 2024 09:35:51 -0700 [thread overview]
Message-ID: <20240429163551.GD360898@frogsfrogsfrogs> (raw)
In-Reply-To: <j6a357qbjsf346khicummgmutjvkircf7ff7gd7for2ajn4k7q@q6dw22io6dcp>
On Mon, Apr 29, 2024 at 12:15:55PM +0200, Andrey Albershteyn wrote:
> On 2024-04-24 11:05:20, Darrick J. Wong wrote:
> > On Thu, Apr 04, 2024 at 11:14:07PM -0400, Eric Biggers wrote:
> > > On Fri, Mar 29, 2024 at 05:35:48PM -0700, Darrick J. Wong wrote:
> > > > From: Darrick J. Wong <djwong@kernel.org>
> > > >
> > > > Now that we've made the verity workqueue per-superblock, we don't need
> > > > the systemwide workqueue. Get rid of the old implementation.
> > >
> > > This commit message needs to be rephrased because this commit isn't just
> > > removing unused code. It's also converting ext4 and f2fs over to the new
> > > workqueue type. (Maybe these two parts belong as separate patches?)
> >
> > Yes, will fix that.
> >
> > > Also, if there are any changes in the workqueue flags that are being used for
> > > ext4 and f2fs, that needs to be documented.
> >
> > Hmm. The current codebase does this:
> >
> > fsverity_read_workqueue = alloc_workqueue("fsverity_read_queue",
> > WQ_HIGHPRI,
> > num_online_cpus());
> >
> > Looking at commit f959325e6ac3 ("fsverity: Remove WQ_UNBOUND from
> > fsverity read workqueue"), I guess you want a bound workqueue so that
> > the CPU that handles the readahead ioend will also handle the verity
> > validation?
> >
> > Why do you set max_active to num_online_cpus()? Is that because the
> > verity hash is (probably?) being computed on the CPUs, and there's only
> > so many of those to go around, so there's little point in making more?
> > Or is it to handle systems with more than WQ_DFL_ACTIVE (~256) CPUs?
> > Maybe there's a different reason?
> >
> > If you add more CPUs to the system later, does this now constrain the
> > number of CPUs that can be participating in verity validation? Why not
> > let the system try to process as many read ioends as are ready to be
> > processed, rather than introducing a constraint here?
> >
> > As for WQ_HIGHPRI, I wish Dave or Andrey would chime in on why this
> > isn't appropriate for XFS. I think they have a reason for this, but the
> > most I can do is speculate that it's to avoid blocking other things in
> > the system.
>
> The log uses WQ_HIGHPRI for journal IO completion
> log->l_ioend_workqueue, as far I understand some data IO completion
> could require a transaction which make a reservation which
> could lead to data IO waiting for journal IO. But if data IO
> completion will be scheduled first this could be a possible
> deadlock... I don't see a particular example, but also I'm not sure
> why to make fs-verity high priority in XFS.
Ah, ok. I'll add a comment about that to my patch then.
> > In Andrey's V5 patch, XFS creates its own the workqueue like this:
> > https://lore.kernel.org/linux-xfs/20240304191046.157464-10-aalbersh@redhat.com/
> >
> > struct workqueue_struct *wq = alloc_workqueue(
> > "pread/%s", (WQ_FREEZABLE | WQ_MEM_RECLAIM), 0, sb->s_id);
> >
> > I don't grok this either -- read ioend workqueues aren't usually
> > involved in memory reclaim at all, and I can't see why you'd want to
> > freeze the verity workqueue during suspend. Reads are allowed on frozen
> > filesystems, so I don't see why verity would be any different.
>
> Yeah maybe freezable can go away, initially I picked those flags as
> most of the other workqueues in xfs are in same configuration.
<nod>
--D
> --
> - Andrey
>
>
next prev parent reply other threads:[~2024-04-29 16:35 UTC|newest]
Thread overview: 111+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-30 0:30 [PATCHBOMB v5.5] fs-verity support for XFS Darrick J. Wong
2024-03-30 0:32 ` [PATCHSET v5.5 1/2] fs-verity: support merkle tree access by blocks Darrick J. Wong
2024-03-30 0:32 ` [PATCH 01/13] fs: add FS_XFLAG_VERITY for verity files Darrick J. Wong
2024-03-30 0:33 ` [PATCH 02/13] fsverity: pass tree_blocksize to end_enable_verity() Darrick J. Wong
2024-03-30 0:33 ` [PATCH 03/13] fsverity: support block-based Merkle tree caching Darrick J. Wong
2024-04-05 2:31 ` Eric Biggers
2024-04-24 21:25 ` Darrick J. Wong
2024-04-24 22:08 ` Eric Biggers
2024-04-25 0:27 ` Darrick J. Wong
2024-04-25 0:46 ` Eric Biggers
2024-04-25 0:53 ` Darrick J. Wong
2024-03-30 0:33 ` [PATCH 04/13] fsverity: add per-sb workqueue for post read processing Darrick J. Wong
2024-04-05 2:39 ` Eric Biggers
2024-04-24 21:33 ` Darrick J. Wong
2024-03-30 0:33 ` [PATCH 05/13] fsverity: add tracepoints Darrick J. Wong
2024-03-30 0:34 ` [PATCH 06/13] fsverity: send the level of the merkle tree block to ->read_merkle_tree_block Darrick J. Wong
2024-04-05 2:42 ` Eric Biggers
2024-04-25 0:30 ` Darrick J. Wong
2024-03-30 0:34 ` [PATCH 07/13] fsverity: pass the new tree size and block size to ->begin_enable_verity Darrick J. Wong
2024-04-05 2:46 ` Eric Biggers
2024-04-24 21:36 ` Darrick J. Wong
2024-03-30 0:34 ` [PATCH 08/13] fsverity: expose merkle tree geometry to callers Darrick J. Wong
2024-04-05 2:50 ` Eric Biggers
2024-04-25 0:45 ` Darrick J. Wong
2024-04-25 0:49 ` Eric Biggers
2024-04-25 1:01 ` Darrick J. Wong
2024-04-25 1:04 ` Eric Biggers
2024-03-30 0:35 ` [PATCH 09/13] fsverity: box up the write_merkle_tree_block parameters too Darrick J. Wong
2024-04-05 2:52 ` Eric Biggers
2024-04-25 0:46 ` Darrick J. Wong
2024-03-30 0:35 ` [PATCH 10/13] fsverity: pass the zero-hash value to the implementation Darrick J. Wong
2024-04-05 2:57 ` Eric Biggers
2024-04-24 19:02 ` Darrick J. Wong
2024-04-24 19:19 ` Eric Biggers
2024-04-24 20:23 ` Darrick J. Wong
2024-04-24 20:59 ` Eric Biggers
2024-04-24 21:43 ` Darrick J. Wong
2024-03-30 0:35 ` [PATCH 11/13] fsverity: report validation errors back to the filesystem Darrick J. Wong
2024-04-05 3:09 ` Eric Biggers
2024-04-24 18:18 ` Darrick J. Wong
2024-04-24 18:52 ` Eric Biggers
2024-04-24 19:03 ` Darrick J. Wong
2024-03-30 0:35 ` [PATCH 12/13] fsverity: remove system-wide workqueue Darrick J. Wong
2024-04-05 3:14 ` Eric Biggers
2024-04-24 18:05 ` Darrick J. Wong
2024-04-24 18:41 ` Eric Biggers
2024-04-29 10:15 ` Andrey Albershteyn
2024-04-29 16:35 ` Darrick J. Wong [this message]
2024-03-30 0:36 ` [PATCH 13/13] iomap: integrate fs-verity verification into iomap's read path Darrick J. Wong
2024-03-30 0:32 ` [PATCHSET v5.5 2/2] xfs: fs-verity support Darrick J. Wong
2024-03-30 0:36 ` [PATCH 01/29] xfs: use unsigned ints for non-negative quantities in xfs_attr_remote.c Darrick J. Wong
2024-04-02 9:51 ` Andrey Albershteyn
2024-04-02 16:25 ` Darrick J. Wong
2024-03-30 0:36 ` [PATCH 02/29] xfs: turn XFS_ATTR3_RMT_BUF_SPACE into a function Darrick J. Wong
2024-04-02 10:09 ` Andrey Albershteyn
2024-03-30 0:36 ` [PATCH 03/29] xfs: create a helper to compute the blockcount of a max sized remote value Darrick J. Wong
2024-04-02 10:09 ` Andrey Albershteyn
2024-03-30 0:37 ` [PATCH 04/29] xfs: minor cleanups of xfs_attr3_rmt_blocks Darrick J. Wong
2024-04-02 10:11 ` Andrey Albershteyn
2024-03-30 0:37 ` [PATCH 05/29] xfs: add attribute type for fs-verity Darrick J. Wong
2024-03-30 0:37 ` [PATCH 06/29] xfs: do not use xfs_attr3_rmt_hdr for remote verity value blocks Darrick J. Wong
2024-03-30 0:37 ` [PATCH 07/29] xfs: add fs-verity ro-compat flag Darrick J. Wong
2024-03-30 0:38 ` [PATCH 08/29] xfs: add inode on-disk VERITY flag Darrick J. Wong
2024-03-30 0:38 ` [PATCH 09/29] xfs: initialize fs-verity on file open and cleanup on inode destruction Darrick J. Wong
2024-03-30 0:38 ` [PATCH 10/29] xfs: don't allow to enable DAX on fs-verity sealed inode Darrick J. Wong
2024-03-30 0:38 ` [PATCH 11/29] xfs: disable direct read path for fs-verity files Darrick J. Wong
2024-03-30 0:39 ` [PATCH 12/29] xfs: widen flags argument to the xfs_iflags_* helpers Darrick J. Wong
2024-04-02 12:37 ` Andrey Albershteyn
2024-04-02 16:27 ` Darrick J. Wong
2024-03-30 0:39 ` [PATCH 13/29] xfs: add fs-verity support Darrick J. Wong
2024-04-02 8:42 ` Andrey Albershteyn
2024-04-02 16:34 ` Darrick J. Wong
2024-04-25 1:14 ` Darrick J. Wong
2024-03-30 0:39 ` [PATCH 14/29] xfs: create a per-mount shrinker for verity inodes merkle tree blocks Darrick J. Wong
2024-04-05 3:16 ` Eric Biggers
2024-04-24 17:39 ` Darrick J. Wong
2024-03-30 0:39 ` [PATCH 15/29] xfs: create an icache tag for files with cached " Darrick J. Wong
2024-03-30 0:40 ` [PATCH 16/29] xfs: shrink verity blob cache Darrick J. Wong
2024-03-30 0:40 ` [PATCH 17/29] xfs: only allow the verity iflag for regular files Darrick J. Wong
2024-04-02 12:52 ` Andrey Albershteyn
2024-03-30 0:40 ` [PATCH 18/29] xfs: don't store trailing zeroes of merkle tree blocks Darrick J. Wong
2024-03-30 0:41 ` [PATCH 19/29] xfs: use merkle tree offset as attr hash Darrick J. Wong
2024-03-30 0:41 ` [PATCH 20/29] xfs: don't bother storing merkle tree blocks for zeroed data blocks Darrick J. Wong
2024-03-30 0:41 ` [PATCH 21/29] xfs: add fs-verity ioctls Darrick J. Wong
2024-03-30 0:41 ` [PATCH 22/29] xfs: advertise fs-verity being available on filesystem Darrick J. Wong
2024-04-02 13:44 ` Andrey Albershteyn
2024-03-30 0:42 ` [PATCH 23/29] xfs: make scrub aware of verity dinode flag Darrick J. Wong
2024-03-30 0:42 ` [PATCH 24/29] xfs: teach online repair to evaluate fsverity xattrs Darrick J. Wong
2024-04-02 15:42 ` Andrey Albershteyn
2024-04-02 16:42 ` Darrick J. Wong
2024-03-30 0:42 ` [PATCH 25/29] xfs: report verity failures through the health system Darrick J. Wong
2024-04-02 16:16 ` Andrey Albershteyn
2024-03-30 0:42 ` [PATCH 26/29] xfs: clear the verity iflag when not appropriate Darrick J. Wong
2024-04-02 16:26 ` Andrey Albershteyn
2024-03-30 0:43 ` [PATCH 27/29] xfs: make it possible to disable fsverity Darrick J. Wong
2024-04-02 17:15 ` Andrey Albershteyn
2024-04-02 23:25 ` Eric Biggers
2024-04-03 1:26 ` Darrick J. Wong
2024-03-30 0:43 ` [PATCH 28/29] xfs: allow verity files to be opened even if the fsverity metadata is damaged Darrick J. Wong
2024-04-02 18:04 ` Andrey Albershteyn
2024-04-02 20:00 ` Colin Walters
2024-04-02 22:52 ` Darrick J. Wong
2024-04-02 23:45 ` Eric Biggers
2024-04-03 1:34 ` Darrick J. Wong
2024-04-03 0:10 ` Colin Walters
2024-04-03 1:39 ` Darrick J. Wong
2024-04-03 1:59 ` Dave Chinner
2024-04-03 3:19 ` Darrick J. Wong
2024-04-03 22:22 ` Dave Chinner
2024-04-03 8:35 ` Alexander Larsson
2024-03-30 0:43 ` [PATCH 29/29] xfs: enable ro-compat fs-verity flag Darrick J. Wong
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