[PATCH 21/21] Unionfs: Correctly decrement refcounts of mnt's upon branch management

Josef 'Jeff' Sipek
2007-05-24T00:37:58Z

The old logic was broken in one place, which another place tried to "fix"
incorrectly. Also added detailed comments to explain the new/correct logic.

Signed-off-by: Erez Zadok <ezk@cs.sunysb.edu>
Signed-off-by: Josef 'Jeff' Sipek <jsipek@cs.sunysb.edu>
---
fs/unionfs/commonfops.c | 17 ++++++++++++-----
fs/unionfs/dentry.c | 18 +++++++++++++-----
2 files changed, 25 insertions(+), 10 deletions(-)

diff --git a/fs/unionfs/commonfops.c b/fs/unionfs/commonfops.c
index 69d9c87..83001aa 100644
--- a/fs/unionfs/commonfops.c
+++ b/fs/unionfs/commonfops.c
@@ -135,14 +135,21 @@ static void cleanup_file(struct file *file)
"file %p\n", file);
else {
unionfs_read_lock(sb);
+ /* decrement count of open files */
branchput(sb, i);
unionfs_read_unlock(sb);
- /* XXX: is it OK to use sb->s_root here? */
- unionfs_mntput(sb->s_root, i);
- /* mntget b/c fput below will call mntput */
- unionfs_mntget(sb->s_root, bindex);
+ /*
+ * fput will perform an mntput for us on the
+ * correct branch. Although we're using the
+ * file's old branch configuration, bindex,
+ * which is the old index, correctly points
+ * to the right branch in the file's branch
+ * list. In other words, we're going to
+ * mntput the correct branch even if
+ * branches have been added/removed.
+ */
+ fput(unionfs_lower_file_idx(file, bindex));
}
- fput(unionfs_lower_file_idx(file, bindex));
}
}

diff --git a/fs/unionfs/dentry.c b/fs/unionfs/dentry.c
index 95cea3b..db0ef43 100644
--- a/fs/unionfs/dentry.c
+++ b/fs/unionfs/dentry.c
@@ -258,14 +258,22 @@ out_this:
/* finally, lock this dentry and revalidate it */
verify_locked(dentry);
dgen = atomic_read(&UNIONFS_D(dentry)->generation);
- saved_bstart = dbstart(dentry);
- saved_bend = dbend(dentry);
valid = __unionfs_d_revalidate_one(dentry, nd);

- if (valid && chain_len > 0 && sbgen != dgen) {
- for (bindex = saved_bstart; bindex <= saved_bend; bindex++)
+ /*
+ * If __unionfs_d_revalidate_one() succeeded above, then it will
+ * have incremented the refcnt of the mnt's, but also the branch
+ * indices of the dentry will have been updated (to take into
+ * account any branch insertions/deletion. So the current
+ * dbstart/dbend match the current, and new, indices of the mnts
+ * which __unionfs_d_revalidate_one has incremented. Note: the "if"
+ * test below does not depend on whether chain_len was 0 or greater.
+ */
+ if (valid && sbgen != dgen)
+ for (bindex = dbstart(dentry);
+ bindex <= dbend(dentry);
+ bindex++)
unionfs_mntput(dentry, bindex);
- }

out_free:
/* unlock/dput all dentries in chain and return status */
--
1.5.2.rc1.165.gaf9b