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authorChris Mason <chris.mason@oracle.com>2011-06-13 20:00:16 -0400
committerChris Mason <chris.mason@oracle.com>2011-06-17 13:36:58 -0400
commit7585717f304f5ed005cc4ad933a69aab3efbd136 (patch)
tree2bbef7f61c61b125778d3631237094594b408e0a /fs/btrfs/relocation.c
parentf4c44016218a6fce357715b9bbabbbbe1f69853c (diff)
downloadlinux-7585717f304f5ed005cc4ad933a69aab3efbd136.tar.gz
Btrfs: fix relocation races
The recent commit to get rid of our trans_mutex introduced some races with block group relocation. The problem is that relocation needs to do some record keeping about each root, and it was relying on the transaction mutex to coordinate things in subtle ways. This fix adds a mutex just for the relocation code and makes sure it doesn't have a big impact on normal operations. The race is really fixed in btrfs_record_root_in_trans, which is where we step back and wait for the relocation code to finish accounting setup. Signed-off-by: Chris Mason <chris.mason@oracle.com>
Diffstat (limited to 'fs/btrfs/relocation.c')
-rw-r--r--fs/btrfs/relocation.c30
1 files changed, 21 insertions, 9 deletions
diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index f25b10a22a0..086b1e6b861 100644
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -1368,7 +1368,7 @@ int btrfs_update_reloc_root(struct btrfs_trans_handle *trans,
int ret;
if (!root->reloc_root)
- return 0;
+ goto out;
reloc_root = root->reloc_root;
root_item = &reloc_root->root_item;
@@ -1390,6 +1390,8 @@ int btrfs_update_reloc_root(struct btrfs_trans_handle *trans,
ret = btrfs_update_root(trans, root->fs_info->tree_root,
&reloc_root->root_key, root_item);
BUG_ON(ret);
+
+out:
return 0;
}
@@ -2142,10 +2144,11 @@ int prepare_to_merge(struct reloc_control *rc, int err)
u64 num_bytes = 0;
int ret;
- spin_lock(&root->fs_info->trans_lock);
+ mutex_lock(&root->fs_info->reloc_mutex);
rc->merging_rsv_size += root->nodesize * (BTRFS_MAX_LEVEL - 1) * 2;
rc->merging_rsv_size += rc->nodes_relocated * 2;
- spin_unlock(&root->fs_info->trans_lock);
+ mutex_unlock(&root->fs_info->reloc_mutex);
+
again:
if (!err) {
num_bytes = rc->merging_rsv_size;
@@ -2214,9 +2217,16 @@ int merge_reloc_roots(struct reloc_control *rc)
int ret;
again:
root = rc->extent_root;
- spin_lock(&root->fs_info->trans_lock);
+
+ /*
+ * this serializes us with btrfs_record_root_in_transaction,
+ * we have to make sure nobody is in the middle of
+ * adding their roots to the list while we are
+ * doing this splice
+ */
+ mutex_lock(&root->fs_info->reloc_mutex);
list_splice_init(&rc->reloc_roots, &reloc_roots);
- spin_unlock(&root->fs_info->trans_lock);
+ mutex_unlock(&root->fs_info->reloc_mutex);
while (!list_empty(&reloc_roots)) {
found = 1;
@@ -3590,17 +3600,19 @@ next:
static void set_reloc_control(struct reloc_control *rc)
{
struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
- spin_lock(&fs_info->trans_lock);
+
+ mutex_lock(&fs_info->reloc_mutex);
fs_info->reloc_ctl = rc;
- spin_unlock(&fs_info->trans_lock);
+ mutex_unlock(&fs_info->reloc_mutex);
}
static void unset_reloc_control(struct reloc_control *rc)
{
struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
- spin_lock(&fs_info->trans_lock);
+
+ mutex_lock(&fs_info->reloc_mutex);
fs_info->reloc_ctl = NULL;
- spin_unlock(&fs_info->trans_lock);
+ mutex_unlock(&fs_info->reloc_mutex);
}
static int check_extent_flags(u64 flags)