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Btrfs: Avoid superfluous tree-log writeout
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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>
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Yan, Zheng authored and Chris Mason committed Dec 16, 2009
1 parent 22763c5 commit 8cef4e1
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Showing 5 changed files with 47 additions and 31 deletions.
6 changes: 3 additions & 3 deletions fs/btrfs/disk-io.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -980,12 +980,12 @@ int btrfs_free_log_root_tree(struct btrfs_trans_handle *trans,

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;

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12 changes: 10 additions & 2 deletions fs/btrfs/extent-tree.c
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Original file line number Diff line number Diff line change
Expand Up @@ -4919,8 +4919,16 @@ struct extent_buffer *btrfs_init_new_buffer(struct btrfs_trans_handle *trans,
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);
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21 changes: 11 additions & 10 deletions fs/btrfs/transaction.c
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Original file line number Diff line number Diff line change
Expand Up @@ -354,7 +354,7 @@ int btrfs_end_transaction_throttle(struct btrfs_trans_handle *trans,
* 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;
Expand All @@ -367,7 +367,7 @@ int btrfs_write_marked_extents(struct btrfs_root *root,

while (1) {
ret = find_first_extent_bit(dirty_pages, start, &start, &end,
EXTENT_DIRTY);
mark);
if (ret)
break;
while (start <= end) {
Expand Down Expand Up @@ -413,7 +413,7 @@ int btrfs_write_marked_extents(struct btrfs_root *root,
* 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;
Expand All @@ -425,12 +425,12 @@ int btrfs_wait_marked_extents(struct btrfs_root *root,
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;
Expand Down Expand Up @@ -460,13 +460,13 @@ int btrfs_wait_marked_extents(struct btrfs_root *root,
* 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;
}

Expand All @@ -479,7 +479,8 @@ int btrfs_write_and_wait_transaction(struct btrfs_trans_handle *trans,
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);
}

/*
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6 changes: 3 additions & 3 deletions fs/btrfs/transaction.h
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Original file line number Diff line number Diff line change
Expand Up @@ -107,10 +107,10 @@ void btrfs_throttle(struct btrfs_root *root);
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
33 changes: 20 additions & 13 deletions fs/btrfs/tree-log.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1977,10 +1977,11 @@ int btrfs_sync_log(struct btrfs_trans_handle *trans,
{
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;
Expand Down Expand Up @@ -2014,24 +2015,29 @@ int btrfs_sync_log(struct btrfs_trans_handle *trans,
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);

Expand All @@ -2052,7 +2058,7 @@ int btrfs_sync_log(struct btrfs_trans_handle *trans,

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);
Expand All @@ -2072,16 +2078,17 @@ int btrfs_sync_log(struct btrfs_trans_handle *trans,
* 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);
Expand Down Expand Up @@ -2147,12 +2154,12 @@ int btrfs_free_log(struct btrfs_trans_handle *trans, struct btrfs_root *root)

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) {
Expand Down

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