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Btrfs: Don't loop forever on metadata IO failures

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When a btrfs metadata read fails, the first thing we try to do is find
a good copy on another mirror of the block.  If this fails, read_tree_block()
ends up returning a buffer that isn't up to date.

The btrfs btree reading code was reworked to drop locks and repeat
the search when IO was done, but the changes didn't add a check for failed
reads.  The end result was looping forever on buffers that were never
going to become up to date.

Signed-off-by: Chris Mason <chris.mason@oracle.com>
This commit is contained in:
Chris Mason 2009-05-14 13:24:30 -04:00
parent 2757495c90
commit 76a05b35a3
1 changed files with 36 additions and 3 deletions
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39
fs/btrfs/ctree.c
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@ -1469,6 +1469,7 @@ read_block_for_search(struct btrfs_trans_handle *trans,
u32 blocksize;
struct extent_buffer *b = *eb_ret;
struct extent_buffer *tmp;
int ret;
blocknr = btrfs_node_blockptr(b, slot);
gen = btrfs_node_ptr_generation(b, slot);
@ -1476,6 +1477,10 @@ read_block_for_search(struct btrfs_trans_handle *trans,
tmp = btrfs_find_tree_block(root, blocknr, blocksize);
if (tmp && btrfs_buffer_uptodate(tmp, gen)) {
/*
* we found an up to date block without sleeping, return
* right away
*/
*eb_ret = tmp;
return 0;
}
@ -1483,7 +1488,9 @@ read_block_for_search(struct btrfs_trans_handle *trans,
/*
* reduce lock contention at high levels
* of the btree by dropping locks before
* we read.
* we read. Don't release the lock on the current
* level because we need to walk this node to figure
* out which blocks to read.
*/
btrfs_unlock_up_safe(p, level + 1);
btrfs_set_path_blocking(p);
@ -1494,10 +1501,21 @@ read_block_for_search(struct btrfs_trans_handle *trans,
reada_for_search(root, p, level, slot, key->objectid);
btrfs_release_path(NULL, p);
ret = -EAGAIN;
tmp = read_tree_block(root, blocknr, blocksize, gen);
if (tmp)
if (tmp) {
/*
* If the read above didn't mark this buffer up to date,
* it will never end up being up to date. Set ret to EIO now
* and give up so that our caller doesn't loop forever
* on our EAGAINs.
*/
if (!btrfs_buffer_uptodate(tmp, 0))
ret = -EIO;
free_extent_buffer(tmp);
return -EAGAIN;
}
return ret;
}
/*
@ -1696,6 +1714,9 @@ cow_done:
if (ret == -EAGAIN)
goto again;
if (ret == -EIO)
goto done;
if (!p->skip_locking) {
int lret;
@ -1738,6 +1759,8 @@ done:
*/
if (!p->leave_spinning)
btrfs_set_path_blocking(p);
if (ret < 0)
btrfs_release_path(root, p);
return ret;
}
@ -4212,6 +4235,11 @@ again:
if (ret == -EAGAIN)
goto again;
if (ret < 0) {
btrfs_release_path(root, path);
goto done;
}
if (!path->skip_locking) {
ret = btrfs_try_spin_lock(next);
if (!ret) {
@ -4246,6 +4274,11 @@ again:
if (ret == -EAGAIN)
goto again;
if (ret < 0) {
btrfs_release_path(root, path);
goto done;
}
if (!path->skip_locking) {
btrfs_assert_tree_locked(path->nodes[level]);
ret = btrfs_try_spin_lock(next);