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Btrfs: fix tree mod log for root replacements at leaf level

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For the tree mod log, we don't log any operations at leaf level. If the root
is at the leaf level (i.e. the tree consists only of the root), then
__tree_mod_log_oldest_root will find a ROOT_REPLACE operation in the log
(because we always log that one no matter which level), but no other
operations.

With this patch __tree_mod_log_oldest_root exits cleanly instead of
BUGging in this situation. get_old_root checks if its really a root at leaf
level in case we don't have any operations and WARNs if this assumption
breaks.

Signed-off-by: Jan Schmidt <list.btrfs@jan-o-sch.net>
This commit is contained in:
Jan Schmidt 2012-06-21 10:59:13 +02:00
parent 9345457f4a
commit 28da9fb446
1 changed files with 15 additions and 13 deletions
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26
fs/btrfs/ctree.c
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@ -1024,11 +1024,18 @@ __tree_mod_log_oldest_root(struct btrfs_fs_info *fs_info,
if (!looped && !tm)
return 0;
/*
* we must have key remove operations in the log before the
* replace operation.
* if there are no tree operation for the oldest root, we simply
* return it. this should only happen if that (old) root is at
* level 0.
*/
BUG_ON(!tm);
if (!tm)
break;
/*
* if there's an operation that's not a root replacement, we
* found the oldest version of our root. normally, we'll find a
* MOD_LOG_KEY_REMOVE_WHILE_FREEING operation here.
*/
if (tm->op != MOD_LOG_ROOT_REPLACE)
break;
@ -1192,16 +1199,8 @@ get_old_root(struct btrfs_root *root, u64 time_seq)
}
tm = tree_mod_log_search(root->fs_info, logical, time_seq);
/*
* there was an item in the log when __tree_mod_log_oldest_root
* returned. this one must not go away, because the time_seq passed to
* us must be blocking its removal.
*/
BUG_ON(!tm);
if (old_root)
eb = alloc_dummy_extent_buffer(tm->index << PAGE_CACHE_SHIFT,
root->nodesize);
eb = alloc_dummy_extent_buffer(logical, root->nodesize);
else
eb = btrfs_clone_extent_buffer(root->node);
btrfs_tree_read_unlock(root->node);
@ -1216,7 +1215,10 @@ get_old_root(struct btrfs_root *root, u64 time_seq)
btrfs_set_header_level(eb, old_root->level);
btrfs_set_header_generation(eb, old_generation);
}
if (tm)
__tree_mod_log_rewind(eb, time_seq, tm);
else
WARN_ON(btrfs_header_level(eb) != 0);
extent_buffer_get(eb);
return eb;