ocfs2: fix regression in ocfs2_read_blocks_sync()

We're panicing in ocfs2_read_blocks_sync() if a jbd-managed buffer is seen.
At first glance, this seems ok but in reality it can happen. My test case
was to just run 'exorcist'. A struct inode is being pushed out of memory but
is then re-read at a later time, before the buffer has been checkpointed by
jbd. This causes a BUG to be hit in ocfs2_read_blocks_sync().

Reviewed-by: Joel Becker <joel.becker@oracle.com>
Signed-off-by: Mark Fasheh <mfasheh@suse.com>

1 files changed, 4 insertions, 11 deletions

diff --git a/fs/ocfs2/buffer_head_io.c b/fs/ocfs2/buffer_head_io.c
index 7e947c672469..3a178ec48d7c 100644
--- a/fs/ocfs2/buffer_head_io.c
+++ b/fs/ocfs2/buffer_head_io.c
@@ -112,7 +112,7 @@ int ocfs2_read_blocks_sync(struct ocfs2_super *osb, u64 block,
                 bh = bhs[i];
 
                 if (buffer_jbd(bh)) {
-                        mlog(ML_ERROR,
+                        mlog(ML_BH_IO,
                              "trying to sync read a jbd "
                              "managed bh (blocknr = %llu), skipping\n",
                              (unsigned long long)bh->b_blocknr);
@@ -147,15 +147,10 @@ int ocfs2_read_blocks_sync(struct ocfs2_super *osb, u64 block,
         for (i = nr; i > 0; i--) {
                 bh = bhs[i - 1];
 
-                if (buffer_jbd(bh)) {
-                        mlog(ML_ERROR,
-                             "the journal got the buffer while it was "
-                             "locked for io! (blocknr = %llu)\n",
-                             (unsigned long long)bh->b_blocknr);
-                        BUG();
-                }
+                /* No need to wait on the buffer if it's managed by JBD. */
+                if (!buffer_jbd(bh))
+                        wait_on_buffer(bh);
 
-                wait_on_buffer(bh);
                 if (!buffer_uptodate(bh)) {
                         /* Status won't be cleared from here on out,
                          * so we can safely record this and loop back
@@ -251,8 +246,6 @@ int ocfs2_read_blocks(struct inode *inode, u64 block, int nr,
                         ignore_cache = 1;
                 }
 
-                /* XXX: Can we ever get this and *not* have the cached
-                 * flag set? */
                 if (buffer_jbd(bh)) {
                         if (ignore_cache)
                                 mlog(ML_BH_IO, "trying to sync read a jbd "