From: "NeilBrown" <neilb@suse.de>
To: "Al Viro" <viro@zeniv.linux.org.uk>
Cc: "Linus Torvalds" <torvalds@linux-foundation.org>,
"Daire Byrne" <daire@dneg.com>,
"Trond Myklebust" <trond.myklebust@hammerspace.com>,
"Chuck Lever" <chuck.lever@oracle.com>,
"Linux NFS Mailing List" <linux-nfs@vger.kernel.org>,
linux-fsdevel@vger.kernel.org,
"LKML" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 09/10] VFS: add LOOKUP_SILLY_RENAME
Date: Mon, 29 Aug 2022 13:15:52 +1000 [thread overview]
Message-ID: <166174295243.27490.1036858614514220411@noble.neil.brown.name> (raw)
In-Reply-To: <YwlxiCt3TvzdEhUl@ZenIV>
On Sat, 27 Aug 2022, Al Viro wrote:
> On Fri, Aug 26, 2022 at 12:10:43PM +1000, NeilBrown wrote:
> > When performing a "silly rename" to avoid removing a file that is still
> > open, we need to perform a lookup in a directory that is already locked.
> >
> > In order to allow common functions to be used for this lookup, introduce
> > LOOKUP_SILLY_RENAME which affirms that the directory is already locked
> > and that the vfsmnt is already writable.
> >
> > When LOOKUP_SILLY_RENAME is set, path->mnt can be NULL. As
> > i_op->rename() doesn't make the vfsmnt available, this is unavoidable.
> > So we ensure that a NULL ->mnt isn't fatal.
>
> This one is really disgusting. Flag-dependent locking is a pretty much
> guaranteed source of PITA and "magical" struct path is, again, asking for
> trouble.
>
> You seem to be trying for simpler call graph and you end up paying with
> control flow that is much harder to reason about.
>
It was mostly about avoiding code duplication.
I'll see if I can find a cleaner way.
Thanks,
NeilBrown
next prev parent reply other threads:[~2022-08-29 3:16 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-26 2:10 [PATCH/RFC 00/10 v5] Improve scalability of directory operations NeilBrown
2022-08-26 2:10 ` [PATCH 09/10] VFS: add LOOKUP_SILLY_RENAME NeilBrown
2022-08-27 1:21 ` Al Viro
2022-08-29 3:15 ` NeilBrown [this message]
2022-08-26 2:10 ` [PATCH 01/10] VFS: support parallel updates in the one directory NeilBrown
2022-08-26 19:06 ` Linus Torvalds
2022-08-26 23:06 ` NeilBrown
2022-08-27 0:13 ` Linus Torvalds
2022-08-27 0:23 ` Al Viro
2022-08-27 21:14 ` Al Viro
2022-08-27 0:17 ` Al Viro
2022-09-01 0:31 ` NeilBrown
2022-09-01 3:44 ` Al Viro
2022-08-27 3:43 ` Al Viro
2022-08-29 1:59 ` NeilBrown
2022-09-03 0:06 ` Al Viro
2022-09-03 1:40 ` NeilBrown
2022-09-03 2:12 ` Al Viro
2022-09-03 17:52 ` Al Viro
2022-09-04 23:33 ` NeilBrown
2022-08-26 2:10 ` [PATCH 08/10] NFSD: allow parallel creates from nfsd NeilBrown
2022-08-27 4:37 ` Al Viro
2022-08-29 3:12 ` NeilBrown
2022-08-26 2:10 ` [PATCH 05/10] VFS: export done_path_update() NeilBrown
2022-08-26 2:10 ` [PATCH 02/10] VFS: move EEXIST and ENOENT tests into lookup_hash_update() NeilBrown
2022-08-26 2:10 ` [PATCH 06/10] VFS: support concurrent renames NeilBrown
2022-08-27 4:12 ` Al Viro
2022-08-29 3:08 ` NeilBrown
2022-08-26 2:10 ` [PATCH 10/10] NFS: support parallel updates in the one directory NeilBrown
2022-08-26 15:31 ` John Stoffel
2022-08-26 23:13 ` NeilBrown
2022-08-26 2:10 ` [PATCH 03/10] VFS: move want_write checks into lookup_hash_update() NeilBrown
2022-08-27 3:48 ` Al Viro
2022-08-26 2:10 ` [PATCH 04/10] VFS: move dput() and mnt_drop_write() into done_path_update() NeilBrown
2022-08-26 2:10 ` [PATCH 07/10] VFS: hold DCACHE_PAR_UPDATE lock across d_revalidate() NeilBrown
2022-08-26 14:42 ` [PATCH/RFC 00/10 v5] Improve scalability of directory operations John Stoffel
2022-08-26 23:30 ` NeilBrown
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