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From: David Howells <dhowells@redhat.com>
To: linux-fsdevel@vger.kernel.org, viro@zeniv.linux.org.uk,
	hch@lst.de, tytso@mit.edu, adilger.kernel@dilger.ca,
	darrick.wong@oracle.com, clm@fb.com, josef@toxicpanda.com,
	dsterba@suse.com
Cc: dhowells@redhat.com, linux-ext4@vger.kernel.org,
	linux-xfs@vger.kernel.org, linux-btrfs@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Making linkat() able to overwrite the target
Date: Tue, 14 Jan 2020 16:34:25 +0000
Message-ID: <3326.1579019665@warthog.procyon.org.uk> (raw)

With my rewrite of fscache and cachefiles:

	https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/log/?h=fscache-iter

when a file gets invalidated by the server - and, under some circumstances,
modified locally - I have the cache create a temporary file with vfs_tmpfile()
that I'd like to just link into place over the old one - but I can't because
vfs_link() doesn't allow you to do that.  Instead I have to either unlink the
old one and then link the new one in or create it elsewhere and rename across.

Would it be possible to make linkat() take a flag, say AT_LINK_REPLACE, that
causes the target to be replaced and not give EEXIST?  Or make it so that
rename() can take a tmpfile as the source and replace the target with that.  I
presume that, either way, this would require journal changes on ext4, xfs and
btrfs.

Thanks,
David


             reply index

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-14 16:34 David Howells [this message]
2020-01-14 17:02 ` Al Viro
2020-01-14 18:06 ` David Howells
2020-01-14 19:37   ` Miklos Szeredi
2020-01-17  0:46   ` Colin Walters
2020-01-17  9:57     ` Amir Goldstein
2020-01-17 11:42   ` David Howells
2020-01-17 16:22     ` Omar Sandoval
2020-01-17 16:39     ` David Howells
2020-01-15  8:36 ` Christoph Hellwig

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