From: Al Viro <viro@zeniv.linux.org.uk>
To: NeilBrown <neilb@suse.de>
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: Sat, 27 Aug 2022 02:21:12 +0100 [thread overview]
Message-ID: <YwlxiCt3TvzdEhUl@ZenIV> (raw)
In-Reply-To: <166147984377.25420.5747334898411663007.stgit@noble.brown>
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.
next prev parent reply other threads:[~2022-08-27 1:21 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 04/10] VFS: move dput() and mnt_drop_write() into done_path_update() 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 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 09/10] VFS: add LOOKUP_SILLY_RENAME NeilBrown
2022-08-27 1:21 ` Al Viro [this message]
2022-08-29 3:15 ` 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 02/10] VFS: move EEXIST and ENOENT tests " 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 05/10] VFS: export 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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