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Btrfs: avoid sleeping in verify_parent_transid while atomic

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verify_parent_transid needs to lock the extent range to make
sure no IO is underway, and so it can safely clear the
uptodate bits if our checks fail.

But, a few callers are using it with spinlocks held.  Most
of the time, the generation numbers are going to match, and
we don't want to switch to a blocking lock just for the error
case.  This adds an atomic flag to verify_parent_transid,
and changes it to return EAGAIN if it needs to block to
properly verifiy things.

Signed-off-by: Chris Mason <chris.mason@oracle.com>
This commit is contained in:
Chris Mason
2012-05-06 07:23:47 -04:00
parent ea9947b439
commit b9fab919b7
5 changed files with 34 additions and 17 deletions
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18
fs/btrfs/disk-io.c
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@@ -323,7 +323,8 @@ static int csum_tree_block(struct btrfs_root *root, struct extent_buffer *buf,
* in the wrong place.
*/
static int verify_parent_transid(struct extent_io_tree *io_tree,
struct extent_buffer *eb, u64 parent_transid)
struct extent_buffer *eb, u64 parent_transid,
int atomic)
{
struct extent_state *cached_state = NULL;
int ret;
@@ -331,6 +332,9 @@ static int verify_parent_transid(struct extent_io_tree *io_tree,
if (!parent_transid || btrfs_header_generation(eb) == parent_transid)
return 0;
if (atomic)
return -EAGAIN;
lock_extent_bits(io_tree, eb->start, eb->start + eb->len - 1,
0, &cached_state);
if (extent_buffer_uptodate(eb) &&
@@ -372,7 +376,8 @@ static int btree_read_extent_buffer_pages(struct btrfs_root *root,
ret = read_extent_buffer_pages(io_tree, eb, start,
WAIT_COMPLETE,
btree_get_extent, mirror_num);
if (!ret && !verify_parent_transid(io_tree, eb, parent_transid))
if (!ret && !verify_parent_transid(io_tree, eb,
parent_transid, 0))
break;
/*
@@ -1202,7 +1207,7 @@ static int __must_check find_and_setup_root(struct btrfs_root *tree_root,
root->commit_root = NULL;
root->node = read_tree_block(root, btrfs_root_bytenr(&root->root_item),
blocksize, generation);
if (!root->node || !btrfs_buffer_uptodate(root->node, generation)) {
if (!root->node || !btrfs_buffer_uptodate(root->node, generation, 0)) {
free_extent_buffer(root->node);
root->node = NULL;
return -EIO;
@@ -3143,7 +3148,8 @@ int close_ctree(struct btrfs_root *root)
return 0;
}
int btrfs_buffer_uptodate(struct extent_buffer *buf, u64 parent_transid)
int btrfs_buffer_uptodate(struct extent_buffer *buf, u64 parent_transid,
int atomic)
{
int ret;
struct inode *btree_inode = buf->pages[0]->mapping->host;
@@ -3153,7 +3159,9 @@ int btrfs_buffer_uptodate(struct extent_buffer *buf, u64 parent_transid)
return ret;
ret = verify_parent_transid(&BTRFS_I(btree_inode)->io_tree, buf,
parent_transid);
parent_transid, atomic);
if (ret == -EAGAIN)
return ret;
return !ret;
}