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Subject[043/111] Btrfs: Avoid superfluous tree-log writeout
2.6.32-stable review patch.  If anyone has any objections, please let us know.

------------------
From: Yan, Zheng <zheng.yan@oracle.com>

commit 8cef4e160d74920ad1725f58c89fd75ec4c4ac38 upstream.

We allow two log transactions at a time, but use same flag
to mark dirty tree-log btree blocks. So we may flush dirty
blocks belonging to newer log transaction when committing a
log transaction. This patch fixes the issue by using two
flags to mark dirty tree-log btree blocks.

Signed-off-by: Yan Zheng <zheng.yan@oracle.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
Acked-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
fs/btrfs/disk-io.c | 6 +++---
fs/btrfs/extent-tree.c | 12 ++++++++++--
fs/btrfs/transaction.c | 21 +++++++++++----------
fs/btrfs/transaction.h | 6 +++---
fs/btrfs/tree-log.c | 33 ++++++++++++++++++++-------------
5 files changed, 47 insertions(+), 31 deletions(-)
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -980,12 +980,12 @@ int btrfs_free_log_root_tree(struct btrf

while (1) {
ret = find_first_extent_bit(&log_root_tree->dirty_log_pages,
- 0, &start, &end, EXTENT_DIRTY);
+ 0, &start, &end, EXTENT_DIRTY | EXTENT_NEW);
if (ret)
break;

- clear_extent_dirty(&log_root_tree->dirty_log_pages,
- start, end, GFP_NOFS);
+ clear_extent_bits(&log_root_tree->dirty_log_pages, start, end,
+ EXTENT_DIRTY | EXTENT_NEW, GFP_NOFS);
}
eb = fs_info->log_root_tree->node;

--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -4919,8 +4919,16 @@ struct extent_buffer *btrfs_init_new_buf
btrfs_set_buffer_uptodate(buf);

if (root->root_key.objectid == BTRFS_TREE_LOG_OBJECTID) {
- set_extent_dirty(&root->dirty_log_pages, buf->start,
- buf->start + buf->len - 1, GFP_NOFS);
+ /*
+ * we allow two log transactions at a time, use different
+ * EXENT bit to differentiate dirty pages.
+ */
+ if (root->log_transid % 2 == 0)
+ set_extent_dirty(&root->dirty_log_pages, buf->start,
+ buf->start + buf->len - 1, GFP_NOFS);
+ else
+ set_extent_new(&root->dirty_log_pages, buf->start,
+ buf->start + buf->len - 1, GFP_NOFS);
} else {
set_extent_dirty(&trans->transaction->dirty_pages, buf->start,
buf->start + buf->len - 1, GFP_NOFS);
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -354,7 +354,7 @@ int btrfs_end_transaction_throttle(struc
* those extents are sent to disk but does not wait on them
*/
int btrfs_write_marked_extents(struct btrfs_root *root,
- struct extent_io_tree *dirty_pages)
+ struct extent_io_tree *dirty_pages, int mark)
{
int ret;
int err = 0;
@@ -367,7 +367,7 @@ int btrfs_write_marked_extents(struct bt

while (1) {
ret = find_first_extent_bit(dirty_pages, start, &start, &end,
- EXTENT_DIRTY);
+ mark);
if (ret)
break;
while (start <= end) {
@@ -413,7 +413,7 @@ int btrfs_write_marked_extents(struct bt
* on all the pages and clear them from the dirty pages state tree
*/
int btrfs_wait_marked_extents(struct btrfs_root *root,
- struct extent_io_tree *dirty_pages)
+ struct extent_io_tree *dirty_pages, int mark)
{
int ret;
int err = 0;
@@ -425,12 +425,12 @@ int btrfs_wait_marked_extents(struct btr
unsigned long index;

while (1) {
- ret = find_first_extent_bit(dirty_pages, 0, &start, &end,
- EXTENT_DIRTY);
+ ret = find_first_extent_bit(dirty_pages, start, &start, &end,
+ mark);
if (ret)
break;

- clear_extent_dirty(dirty_pages, start, end, GFP_NOFS);
+ clear_extent_bits(dirty_pages, start, end, mark, GFP_NOFS);
while (start <= end) {
index = start >> PAGE_CACHE_SHIFT;
start = (u64)(index + 1) << PAGE_CACHE_SHIFT;
@@ -460,13 +460,13 @@ int btrfs_wait_marked_extents(struct btr
* those extents are on disk for transaction or log commit
*/
int btrfs_write_and_wait_marked_extents(struct btrfs_root *root,
- struct extent_io_tree *dirty_pages)
+ struct extent_io_tree *dirty_pages, int mark)
{
int ret;
int ret2;

- ret = btrfs_write_marked_extents(root, dirty_pages);
- ret2 = btrfs_wait_marked_extents(root, dirty_pages);
+ ret = btrfs_write_marked_extents(root, dirty_pages, mark);
+ ret2 = btrfs_wait_marked_extents(root, dirty_pages, mark);
return ret || ret2;
}

@@ -479,7 +479,8 @@ int btrfs_write_and_wait_transaction(str
return filemap_write_and_wait(btree_inode->i_mapping);
}
return btrfs_write_and_wait_marked_extents(root,
- &trans->transaction->dirty_pages);
+ &trans->transaction->dirty_pages,
+ EXTENT_DIRTY);
}

/*
--- a/fs/btrfs/transaction.h
+++ b/fs/btrfs/transaction.h
@@ -107,10 +107,10 @@ void btrfs_throttle(struct btrfs_root *r
int btrfs_record_root_in_trans(struct btrfs_trans_handle *trans,
struct btrfs_root *root);
int btrfs_write_and_wait_marked_extents(struct btrfs_root *root,
- struct extent_io_tree *dirty_pages);
+ struct extent_io_tree *dirty_pages, int mark);
int btrfs_write_marked_extents(struct btrfs_root *root,
- struct extent_io_tree *dirty_pages);
+ struct extent_io_tree *dirty_pages, int mark);
int btrfs_wait_marked_extents(struct btrfs_root *root,
- struct extent_io_tree *dirty_pages);
+ struct extent_io_tree *dirty_pages, int mark);
int btrfs_transaction_in_commit(struct btrfs_fs_info *info);
#endif
--- a/fs/btrfs/tree-log.c
+++ b/fs/btrfs/tree-log.c
@@ -1977,10 +1977,11 @@ int btrfs_sync_log(struct btrfs_trans_ha
{
int index1;
int index2;
+ int mark;
int ret;
struct btrfs_root *log = root->log_root;
struct btrfs_root *log_root_tree = root->fs_info->log_root_tree;
- u64 log_transid = 0;
+ unsigned long log_transid = 0;

mutex_lock(&root->log_mutex);
index1 = root->log_transid % 2;
@@ -2014,24 +2015,29 @@ int btrfs_sync_log(struct btrfs_trans_ha
goto out;
}

+ log_transid = root->log_transid;
+ if (log_transid % 2 == 0)
+ mark = EXTENT_DIRTY;
+ else
+ mark = EXTENT_NEW;
+
/* we start IO on all the marked extents here, but we don't actually
* wait for them until later.
*/
- ret = btrfs_write_marked_extents(log, &log->dirty_log_pages);
+ ret = btrfs_write_marked_extents(log, &log->dirty_log_pages, mark);
BUG_ON(ret);

btrfs_set_root_node(&log->root_item, log->node);

root->log_batch = 0;
- log_transid = root->log_transid;
root->log_transid++;
log->log_transid = root->log_transid;
root->log_start_pid = 0;
smp_mb();
/*
- * log tree has been flushed to disk, new modifications of
- * the log will be written to new positions. so it's safe to
- * allow log writers to go in.
+ * IO has been started, blocks of the log tree have WRITTEN flag set
+ * in their headers. new modifications of the log will be written to
+ * new positions. so it's safe to allow log writers to go in.
*/
mutex_unlock(&root->log_mutex);

@@ -2052,7 +2058,7 @@ int btrfs_sync_log(struct btrfs_trans_ha

index2 = log_root_tree->log_transid % 2;
if (atomic_read(&log_root_tree->log_commit[index2])) {
- btrfs_wait_marked_extents(log, &log->dirty_log_pages);
+ btrfs_wait_marked_extents(log, &log->dirty_log_pages, mark);
wait_log_commit(trans, log_root_tree,
log_root_tree->log_transid);
mutex_unlock(&log_root_tree->log_mutex);
@@ -2072,16 +2078,17 @@ int btrfs_sync_log(struct btrfs_trans_ha
* check the full commit flag again
*/
if (root->fs_info->last_trans_log_full_commit == trans->transid) {
- btrfs_wait_marked_extents(log, &log->dirty_log_pages);
+ btrfs_wait_marked_extents(log, &log->dirty_log_pages, mark);
mutex_unlock(&log_root_tree->log_mutex);
ret = -EAGAIN;
goto out_wake_log_root;
}

ret = btrfs_write_and_wait_marked_extents(log_root_tree,
- &log_root_tree->dirty_log_pages);
+ &log_root_tree->dirty_log_pages,
+ EXTENT_DIRTY | EXTENT_NEW);
BUG_ON(ret);
- btrfs_wait_marked_extents(log, &log->dirty_log_pages);
+ btrfs_wait_marked_extents(log, &log->dirty_log_pages, mark);

btrfs_set_super_log_root(&root->fs_info->super_for_commit,
log_root_tree->node->start);
@@ -2147,12 +2154,12 @@ int btrfs_free_log(struct btrfs_trans_ha

while (1) {
ret = find_first_extent_bit(&log->dirty_log_pages,
- 0, &start, &end, EXTENT_DIRTY);
+ 0, &start, &end, EXTENT_DIRTY | EXTENT_NEW);
if (ret)
break;

- clear_extent_dirty(&log->dirty_log_pages,
- start, end, GFP_NOFS);
+ clear_extent_bits(&log->dirty_log_pages, start, end,
+ EXTENT_DIRTY | EXTENT_NEW, GFP_NOFS);
}

if (log->log_transid > 0) {



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