GFS2: Support for I/O barriers
This patch adds barrier support to GFS2. There is not a lot of change
really... we just add the barrier flag when we write journal header
blocks. If the underlying device refuses to support them, we fall back
to the previous way of doing things (wait for the I/O and hope) since
there is nothing else we can do. There is no user configuration,
barriers will always be on unless the device refuses to support them.
This seems a reasonable solution to me since this is a correctness
issue.
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
index 6c6af9f..ad30585 100644
--- a/fs/gfs2/log.c
+++ b/fs/gfs2/log.c
@@ -18,6 +18,7 @@
#include <linux/delay.h>
#include <linux/kthread.h>
#include <linux/freezer.h>
+#include <linux/bio.h>
#include "gfs2.h"
#include "incore.h"
@@ -584,7 +585,6 @@
memset(bh->b_data, 0, bh->b_size);
set_buffer_uptodate(bh);
clear_buffer_dirty(bh);
- unlock_buffer(bh);
gfs2_ail1_empty(sdp, 0);
tail = current_tail(sdp);
@@ -601,8 +601,23 @@
hash = gfs2_disk_hash(bh->b_data, sizeof(struct gfs2_log_header));
lh->lh_hash = cpu_to_be32(hash);
- set_buffer_dirty(bh);
- if (sync_dirty_buffer(bh))
+ bh->b_end_io = end_buffer_write_sync;
+ if (test_bit(SDF_NOBARRIERS, &sdp->sd_flags))
+ goto skip_barrier;
+ get_bh(bh);
+ submit_bh(WRITE_BARRIER | (1 << BIO_RW_META), bh);
+ wait_on_buffer(bh);
+ if (buffer_eopnotsupp(bh)) {
+ clear_buffer_eopnotsupp(bh);
+ set_buffer_uptodate(bh);
+ set_bit(SDF_NOBARRIERS, &sdp->sd_flags);
+ lock_buffer(bh);
+skip_barrier:
+ get_bh(bh);
+ submit_bh(WRITE_SYNC | (1 << BIO_RW_META), bh);
+ wait_on_buffer(bh);
+ }
+ if (!buffer_uptodate(bh))
gfs2_io_error_bh(sdp, bh);
brelse(bh);