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Subject[PATCH] gfs2: Stop using rhashtable_walk_peek
Date
Function rhashtable_walk_peek is problematic because there is no
guarantee that the glock previously returned still exists; when that key
is deleted, rhashtable_walk_peek can end up returning a different key,
which would cause an inconsistent glock dump. So instead of using
rhashtable_walk_peek, keep track of the current glock in the seq file
iterator functions.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
---
fs/gfs2/glock.c | 18 +++++++++++++-----
1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
index 82fb5583445c..f1fc353875d3 100644
--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -55,6 +55,7 @@ struct gfs2_glock_iter {
struct gfs2_sbd *sdp; /* incore superblock */
struct rhashtable_iter hti; /* rhashtable iterator */
struct gfs2_glock *gl; /* current glock struct */
+ bool gl_held;
loff_t last_pos; /* last position */
};

@@ -1923,9 +1924,11 @@ void gfs2_glock_exit(void)

static void gfs2_glock_iter_next(struct gfs2_glock_iter *gi, loff_t n)
{
- if (n == 0)
- gi->gl = rhashtable_walk_peek(&gi->hti);
- else {
+ if (n != 0 || !gi->gl) {
+ if (gi->gl_held) {
+ gfs2_glock_queue_put(gi->gl);
+ gi->gl_held = false;
+ }
gi->gl = rhashtable_walk_next(&gi->hti);
n--;
}
@@ -1988,7 +1991,10 @@ static void gfs2_glock_seq_stop(struct seq_file *seq, void *iter_ptr)
{
struct gfs2_glock_iter *gi = seq->private;

- gi->gl = NULL;
+ if (gi->gl) {
+ lockref_get(&gi->gl->gl_lockref);
+ gi->gl_held = true;
+ }
rhashtable_walk_stop(&gi->hti);
}

@@ -2061,6 +2067,7 @@ static int __gfs2_glocks_open(struct inode *inode, struct file *file,
*/
gi->last_pos = -1;
gi->gl = NULL;
+ gi->gl_held = false;
rhashtable_walk_enter(&gl_hash_table, &gi->hti);
}
return ret;
@@ -2076,7 +2083,8 @@ static int gfs2_glocks_release(struct inode *inode, struct file *file)
struct seq_file *seq = file->private_data;
struct gfs2_glock_iter *gi = seq->private;

- gi->gl = NULL;
+ if (gi->gl_held)
+ gfs2_glock_put(gi->gl);
rhashtable_walk_exit(&gi->hti);
return seq_release_private(inode, file);
}
--
2.14.3
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