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authorJosef Bacik <jbacik@fb.com>2014-03-28 17:16:01 -0400
committerChris Mason <clm@fb.com>2014-04-07 09:08:39 -0700
commit3f8a18cc53bd1be26eb5b5247e1386ad0e21b623 (patch)
tree266eeb3baf38b968ae2186575ae70ef431cf159f
parent9e351cc862b098d8ec8f8022d110932490794925 (diff)
downloadlinux-3f8a18cc53bd1be26eb5b5247e1386ad0e21b623.tar.bz2
Btrfs: hold the commit_root_sem when getting the commit root during send
We currently rely too heavily on roots being read-only to save us from just accessing root->commit_root. We can easily balance blocks out from underneath a read only root, so to save us from getting screwed make sure we only access root->commit_root under the commit root sem. Thanks, Signed-off-by: Josef Bacik <jbacik@fb.com> Signed-off-by: Chris Mason <clm@fb.com>
-rw-r--r--fs/btrfs/ctree.c6
-rw-r--r--fs/btrfs/ctree.h1
-rw-r--r--fs/btrfs/send.c48
3 files changed, 39 insertions, 16 deletions
diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index 9d89c1648e8e..1bcfcdb23cf4 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -2769,9 +2769,13 @@ again:
* the commit roots are read only
* so we always do read locks
*/
+ if (p->need_commit_sem)
+ down_read(&root->fs_info->commit_root_sem);
b = root->commit_root;
extent_buffer_get(b);
level = btrfs_header_level(b);
+ if (p->need_commit_sem)
+ up_read(&root->fs_info->commit_root_sem);
if (!p->skip_locking)
btrfs_tree_read_lock(b);
} else {
@@ -5436,6 +5440,7 @@ int btrfs_compare_trees(struct btrfs_root *left_root,
* the right if possible or go up and right.
*/
+ down_read(&left_root->fs_info->commit_root_sem);
left_level = btrfs_header_level(left_root->commit_root);
left_root_level = left_level;
left_path->nodes[left_level] = left_root->commit_root;
@@ -5445,6 +5450,7 @@ int btrfs_compare_trees(struct btrfs_root *left_root,
right_root_level = right_level;
right_path->nodes[right_level] = right_root->commit_root;
extent_buffer_get(right_path->nodes[right_level]);
+ up_read(&left_root->fs_info->commit_root_sem);
if (left_level == 0)
btrfs_item_key_to_cpu(left_path->nodes[left_level],
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 4253ab257c9c..d8a669ed5506 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -609,6 +609,7 @@ struct btrfs_path {
unsigned int skip_locking:1;
unsigned int leave_spinning:1;
unsigned int search_commit_root:1;
+ unsigned int need_commit_sem:1;
};
/*
diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
index 6b5f13659317..ab34a23838ef 100644
--- a/fs/btrfs/send.c
+++ b/fs/btrfs/send.c
@@ -493,6 +493,7 @@ static struct btrfs_path *alloc_path_for_send(void)
return NULL;
path->search_commit_root = 1;
path->skip_locking = 1;
+ path->need_commit_sem = 1;
return path;
}
@@ -771,29 +772,22 @@ out:
/*
* Helper function to retrieve some fields from an inode item.
*/
-static int get_inode_info(struct btrfs_root *root,
- u64 ino, u64 *size, u64 *gen,
- u64 *mode, u64 *uid, u64 *gid,
- u64 *rdev)
+static int __get_inode_info(struct btrfs_root *root, struct btrfs_path *path,
+ u64 ino, u64 *size, u64 *gen, u64 *mode, u64 *uid,
+ u64 *gid, u64 *rdev)
{
int ret;
struct btrfs_inode_item *ii;
struct btrfs_key key;
- struct btrfs_path *path;
-
- path = alloc_path_for_send();
- if (!path)
- return -ENOMEM;
key.objectid = ino;
key.type = BTRFS_INODE_ITEM_KEY;
key.offset = 0;
ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
- if (ret < 0)
- goto out;
if (ret) {
- ret = -ENOENT;
- goto out;
+ if (ret > 0)
+ ret = -ENOENT;
+ return ret;
}
ii = btrfs_item_ptr(path->nodes[0], path->slots[0],
@@ -811,7 +805,22 @@ static int get_inode_info(struct btrfs_root *root,
if (rdev)
*rdev = btrfs_inode_rdev(path->nodes[0], ii);
-out:
+ return ret;
+}
+
+static int get_inode_info(struct btrfs_root *root,
+ u64 ino, u64 *size, u64 *gen,
+ u64 *mode, u64 *uid, u64 *gid,
+ u64 *rdev)
+{
+ struct btrfs_path *path;
+ int ret;
+
+ path = alloc_path_for_send();
+ if (!path)
+ return -ENOMEM;
+ ret = __get_inode_info(root, path, ino, size, gen, mode, uid, gid,
+ rdev);
btrfs_free_path(path);
return ret;
}
@@ -1085,6 +1094,7 @@ out:
struct backref_ctx {
struct send_ctx *sctx;
+ struct btrfs_path *path;
/* number of total found references */
u64 found;
@@ -1155,8 +1165,9 @@ static int __iterate_backrefs(u64 ino, u64 offset, u64 root, void *ctx_)
* There are inodes that have extents that lie behind its i_size. Don't
* accept clones from these extents.
*/
- ret = get_inode_info(found->root, ino, &i_size, NULL, NULL, NULL, NULL,
- NULL);
+ ret = __get_inode_info(found->root, bctx->path, ino, &i_size, NULL, NULL,
+ NULL, NULL, NULL);
+ btrfs_release_path(bctx->path);
if (ret < 0)
return ret;
@@ -1235,12 +1246,17 @@ static int find_extent_clone(struct send_ctx *sctx,
if (!tmp_path)
return -ENOMEM;
+ /* We only use this path under the commit sem */
+ tmp_path->need_commit_sem = 0;
+
backref_ctx = kmalloc(sizeof(*backref_ctx), GFP_NOFS);
if (!backref_ctx) {
ret = -ENOMEM;
goto out;
}
+ backref_ctx->path = tmp_path;
+
if (data_offset >= ino_size) {
/*
* There may be extents that lie behind the file's size.