From: James Yonan <email@example.com>
To: Amir Goldstein <firstname.lastname@example.org>
Cc: linux-fsdevel <email@example.com>,
Linux API <firstname.lastname@example.org>
Subject: Re: [PATCH] namei: implemented RENAME_NEWER flag for renameat2() conditional replace
Date: Thu, 30 Jun 2022 10:18:28 -0600 [thread overview]
Message-ID: <email@example.com> (raw)
On 6/28/22 23:15, Amir Goldstein wrote:
>> because the application layer has already done the heavy lifting on the
>> networking side so that the filesystem layer can be local, fast, and
>> atomic. So yes, I haven't tested this yet on networked filesystems.
>> But I'm thinking that because all functionality is implemented at the
>> VFS layer, it should be portable to any fs that also supports
>> RENAME_NOREPLACE, with the caveat that it depends on the ability of the
>> VFS to get a current and accurate mtime attribute inside the critical
>> section between lock_rename() and unlock_rename().
> The implementation is generic. You just implement the logic in the vfs and
> enable it for a few tested filesystems and whoever wants to join the party
> is welcome to test their own filesystems and opt-in to the new flag whether
> they like. Nothing wrong with that.
> w.r.t stability of i_mtime, if I am not mistaken i_mtime itself is
> stable with inode
> lock held (i.e. after lock_two_nondirectories()), however, as Dave pointed out,
> the file's data can be modified in page cache, so as long as the file is open
> for write or mmaped writable, the check of mtime is not atomic.
> Neil's suggestion to deny the operation on open files makes sense.
> You can use a variant of deny_write_access() that takes inode
> which implies the error ETXTBSY for an attempt to exchange newer
> with a file that is open for write.
So I will incorporate these suggestions into an upcoming v2 patch.
next prev parent reply other threads:[~2022-06-30 16:18 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-27 22:11 [PATCH] namei: implemented RENAME_NEWER flag for renameat2() conditional replace James Yonan
2022-06-28 9:46 ` Amir Goldstein
2022-06-28 21:56 ` James Yonan
2022-06-29 5:15 ` Amir Goldstein
2022-06-30 16:18 ` James Yonan [this message]
2022-06-28 17:34 ` Al Viro
2022-06-28 18:34 ` Amir Goldstein
2022-06-28 23:19 ` James Yonan
2022-06-29 1:43 ` Dave Chinner
2022-06-29 2:07 ` NeilBrown
2022-06-29 2:35 ` Dave Chinner
2022-06-29 2:49 ` NeilBrown
2022-06-30 16:39 ` James Yonan
2022-07-01 9:23 ` [PATCH v2] namei: implemented RENAME_NEWER_MTIME " James Yonan
2022-07-01 10:34 ` Amir Goldstein
2022-07-01 20:06 ` James Yonan
2022-07-02 8:07 ` Dave Chinner
2022-07-05 13:30 ` [PATCH v3 1/2] RENAME_NEWER_MTIME is a new userspace-visible flag for renameat2(), and stands alongside existing flags including RENAME_NOREPLACE, RENAME_EXCHANGE, and RENAME_WHITEOUT James Yonan
2022-07-05 13:30 ` [PATCH v3 2/2] selftests: added a new target renameat2 James Yonan
2022-07-05 13:30 ` [PATCH man-pages] rename.2: document new renameat2() flag RENAME_NEWER_MTIME James Yonan
2022-07-05 14:03 ` [RESEND PATCH v3 1/2] namei: implemented RENAME_NEWER_MTIME flag for renameat2() conditional replace James Yonan
2022-07-11 19:13 ` [PATCH v4 " James Yonan
2022-07-11 19:13 ` [PATCH v4 2/2] selftests: added a new target renameat2 James Yonan
2022-07-11 23:10 ` [PATCH v4 1/2] namei: implemented RENAME_NEWER_MTIME flag for renameat2() conditional replace Dave Chinner
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