From: Omar Sandoval <firstname.lastname@example.org>
To: Christoph Hellwig <email@example.com>
Cc: Al Viro <firstname.lastname@example.org>,
Linus Torvalds <email@example.com>,
Xi Wang <firstname.lastname@example.org>
Subject: Re: [RFC PATCH v3 0/2] fs: add AT_REPLACE flag for linkat()
Date: Tue, 24 Apr 2018 08:26:10 -0700 [thread overview]
Message-ID: <20180424152610.GA6989@vader> (raw)
On Tue, Apr 24, 2018 at 06:21:07AM -0700, Christoph Hellwig wrote:
> > Patch 1 implements the VFS support for this flag. The implementation
> > resembles sys_renameat2(), and I took care to preserve all of the
> > original error cases and make the new error cases consistent with
> > rename.
> Shouldn't we try to reuse the rename code and the ->rename method
> instead of largely duplicating it?
As I mentioned in my cover letter, I did try, and it was uglier to reuse
For O_TMPFILE, we can't pass a meaningful old_dir to ->rename(), so now
every ->rename() supporting AT_EMPTY_PATH has to grow a bunch of special
cases for ignoring old_dir (I looked at Btrfs, ext4, and XFS, and it'd
be messy for all three). Conversely, ->link() just needs the extra
unlink before link logic (I added ->link2() for this RFC, but for the
actual patch I'll just add the flag to ->link()).
On the VFS side, in my opinion, there isn't that much duplication -- we
have the may_delete()/is_local_mountpoint() a la unlink, delegation
handling, and some specific error cases we need to handle similarly to
rename, but that's not too suprising for a new primitive.
> In fact I wonder if a better interface would just use renameat(2)
> and accept the AT_EMPTY_PATH (for the source name only).
renameat() makes sense for the O_TMPFILE case, but linkat() + AT_REPLACE
also supports a normal, named source file, and renameat() +
AT_EMPTY_PATH for that doesn't make sense at all (rename this file by
file descriptor, but don't really rename it?).
next prev parent reply other threads:[~2018-04-24 15:26 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-24 6:19 [RFC PATCH v3 0/2] fs: add AT_REPLACE flag for linkat() Omar Sandoval
2018-04-24 6:19 ` [RFC PATCH v3 1/2] fs: add AT_REPLACE flag for linkat() which replaces the target Omar Sandoval
2018-04-24 22:14 ` Omar Sandoval
2018-04-24 6:19 ` [RFC PATCH v3 2/2] Btrfs: add support for linkat() AT_REPLACE Omar Sandoval
2018-04-24 13:21 ` [RFC PATCH v3 0/2] fs: add AT_REPLACE flag for linkat() Christoph Hellwig
2018-04-24 15:26 ` Omar Sandoval [this message]
2018-04-26 7:49 ` Omar Sandoval
2018-04-27 12:00 ` Michael Kerrisk (man-pages)
2018-05-04 18:29 ` Omar Sandoval
2018-05-04 18:30 ` Omar Sandoval
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