VFS: allow filesystems to implement atomic open+truncate
Add a new attribute flag ATTR_OPEN, with the meaning: "truncation was initiated by open() due to the O_TRUNC flag". This way filesystems wanting to implement truncation within their ->open() method can ignore such truncate requests. This is a quick & dirty hack, but it comes for free. Signed-off-by: Miklos Szeredi <mszeredi@suse.cz> Cc: Christoph Hellwig <hch@lst.de> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Andreas Dilger <adilger@clusterfs.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -1660,7 +1660,9 @@ int may_open(struct nameidata *nd, int acc_mode, int flag)
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if (!error) {
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if (!error) {
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DQUOT_INIT(inode);
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DQUOT_INIT(inode);
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error = do_truncate(dentry, 0, ATTR_MTIME|ATTR_CTIME, NULL);
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error = do_truncate(dentry, 0,
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ATTR_MTIME|ATTR_CTIME|ATTR_OPEN,
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NULL);
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}
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}
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put_write_access(inode);
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put_write_access(inode);
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if (error)
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if (error)
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@ -330,6 +330,7 @@ typedef void (dio_iodone_t)(struct kiocb *iocb, loff_t offset,
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#define ATTR_KILL_SGID 4096
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#define ATTR_KILL_SGID 4096
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#define ATTR_FILE 8192
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#define ATTR_FILE 8192
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#define ATTR_KILL_PRIV 16384
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#define ATTR_KILL_PRIV 16384
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#define ATTR_OPEN 32768 /* Truncating from open(O_TRUNC) */
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/*
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/*
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* This is the Inode Attributes structure, used for notify_change(). It
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* This is the Inode Attributes structure, used for notify_change(). It
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