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ocfs2: Explain t_is_new in ocfs2_cp_xattr_cluster(). 

I was unsure of the JOURNAL_ACCESS parameters in
ocfs2_cp_xattr_cluster().  They're based on the function argument
't_is_new', but I couldn't quite figure out how t_is_new mapped to
allocation.  ocfs2_cp_xattr_cluster() actually overwrites the target,
regardless of t_is_new.

Well, I just figured it out.  So I'm adding a big fat comment for those
who come after me.  ocfs2_divide_xattr_cluster() has the same behavior.

Signed-off-by: Joel Becker <joel.becker@oracle.com>
Signed-off-by: Mark Fasheh <mfasheh@suse.com>
This commit is contained in:
Joel Becker 2008-11-25 19:00:15 -08:00 committed by Mark Fasheh
parent 15d609293d
commit 2b656c1d6f
1 changed files with 17 additions and 0 deletions
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17
fs/ocfs2/xattr.c
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@ -3747,6 +3747,11 @@ static int ocfs2_divide_xattr_bucket(struct inode *inode,
goto out;
}
/*
* Hey, if we're overwriting t_bucket, what difference does
* ACCESS_CREATE vs ACCESS_WRITE make? See the comment in the
* same part of ocfs2_cp_xattr_bucket().
*/
ret = ocfs2_xattr_bucket_journal_access(handle, t_bucket,
new_bucket_head ?
OCFS2_JOURNAL_ACCESS_CREATE :
@ -3918,6 +3923,18 @@ static int ocfs2_cp_xattr_bucket(struct inode *inode,
if (ret)
goto out;
/*
* Hey, if we're overwriting t_bucket, what difference does
* ACCESS_CREATE vs ACCESS_WRITE make? Well, if we allocated a new
* cluster to fill, we came here from ocfs2_cp_xattr_cluster(), and
* it is really new - ACCESS_CREATE is required. But we also
* might have moved data out of t_bucket before extending back
* into it. ocfs2_add_new_xattr_bucket() can do this - its call
* to ocfs2_add_new_xattr_cluster() may have created a new extent
* and copied out the end of the old extent. Then it re-extends
* the old extent back to create space for new xattrs. That's
* how we get here, and the bucket isn't really new.
*/
ret = ocfs2_xattr_bucket_journal_access(handle, t_bucket,
t_is_new ?
OCFS2_JOURNAL_ACCESS_CREATE :