[GFS2] Fix race in logging code
The log lock is dropped prior to io submittion, but
this exposes a hole in which the log data structures
may be going away due to a truncate.
Store the buffer head in a local pointer prior to
dropping the lock and relay on the buffer_head lock
for consitency on the buffer head.
Signed-Off-By: Russell Cattelan <cattelan@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
diff --git a/fs/gfs2/lops.c b/fs/gfs2/lops.c
index 8a654cd..4d7f94d 100644
--- a/fs/gfs2/lops.c
+++ b/fs/gfs2/lops.c
@@ -509,7 +509,7 @@
{
LIST_HEAD(started);
struct gfs2_bufdata *bd1 = NULL, *bd2, *bdt;
- struct buffer_head *bh = NULL;
+ struct buffer_head *bh = NULL,*bh1 = NULL;
unsigned int offset = sizeof(struct gfs2_log_descriptor);
struct gfs2_log_descriptor *ld;
unsigned int limit;
@@ -537,8 +537,13 @@
list_for_each_entry_safe_continue(bd1, bdt,
&sdp->sd_log_le_databuf,
bd_le.le_list) {
+ /* store off the buffer head in a local ptr since
+ * gfs2_bufdata might change when we drop the log lock
+ */
+ bh1 = bd1->bd_bh;
+
/* An ordered write buffer */
- if (bd1->bd_bh && !buffer_pinned(bd1->bd_bh)) {
+ if (bh1 && !buffer_pinned(bh1)) {
list_move(&bd1->bd_le.le_list, &started);
if (bd1 == bd2) {
bd2 = NULL;
@@ -547,20 +552,21 @@
bd_le.le_list);
}
total_dbuf--;
- if (bd1->bd_bh) {
- get_bh(bd1->bd_bh);
- if (buffer_dirty(bd1->bd_bh)) {
+ if (bh1) {
+ if (buffer_dirty(bh1)) {
+ get_bh(bh1);
+
gfs2_log_unlock(sdp);
- wait_on_buffer(bd1->bd_bh);
- ll_rw_block(WRITE, 1,
- &bd1->bd_bh);
+
+ ll_rw_block(SWRITE, 1, &bh1);
+ brelse(bh1);
+
gfs2_log_lock(sdp);
}
- brelse(bd1->bd_bh);
continue;
}
continue;
- } else if (bd1->bd_bh) { /* A journaled buffer */
+ } else if (bh1) { /* A journaled buffer */
int magic;
gfs2_log_unlock(sdp);
if (!bh) {
@@ -582,16 +588,16 @@
ld->ld_data2 = cpu_to_be32(0);
memset(ld->ld_reserved, 0, sizeof(ld->ld_reserved));
}
- magic = gfs2_check_magic(bd1->bd_bh);
- *ptr++ = cpu_to_be64(bd1->bd_bh->b_blocknr);
+ magic = gfs2_check_magic(bh1);
+ *ptr++ = cpu_to_be64(bh1->b_blocknr);
*ptr++ = cpu_to_be64((__u64)magic);
- clear_buffer_escaped(bd1->bd_bh);
+ clear_buffer_escaped(bh1);
if (unlikely(magic != 0))
- set_buffer_escaped(bd1->bd_bh);
+ set_buffer_escaped(bh1);
gfs2_log_lock(sdp);
if (n++ > num)
break;
- } else if (!bd1->bd_bh) {
+ } else if (!bh1) {
total_dbuf--;
sdp->sd_log_num_databuf--;
list_del_init(&bd1->bd_le.le_list);