Btrfs: add missing read locks in backref.c
iref_to_path and iterate_irefs both increment the eb's refcount to use it
after releasing the path. Both depend on consistent data remaining in the
extent buffer and need a read lock to protect it.
Signed-off-by: Jan Schmidt <list.btrfs@jan-o-sch.net>
diff --git a/fs/btrfs/backref.c b/fs/btrfs/backref.c
index fb56bcc..bcec067 100644
--- a/fs/btrfs/backref.c
+++ b/fs/btrfs/backref.c
@@ -22,6 +22,7 @@
#include "ulist.h"
#include "transaction.h"
#include "delayed-ref.h"
+#include "locking.h"
/*
* this structure records all encountered refs on the way up to the root
@@ -893,18 +894,22 @@
s64 bytes_left = size - 1;
struct extent_buffer *eb = eb_in;
struct btrfs_key found_key;
+ int leave_spinning = path->leave_spinning;
if (bytes_left >= 0)
dest[bytes_left] = '\0';
+ path->leave_spinning = 1;
while (1) {
len = btrfs_inode_ref_name_len(eb, iref);
bytes_left -= len;
if (bytes_left >= 0)
read_extent_buffer(eb, dest + bytes_left,
(unsigned long)(iref + 1), len);
- if (eb != eb_in)
+ if (eb != eb_in) {
+ btrfs_tree_read_unlock_blocking(eb);
free_extent_buffer(eb);
+ }
ret = inode_ref_info(parent, 0, fs_root, path, &found_key);
if (ret > 0)
ret = -ENOENT;
@@ -919,8 +924,11 @@
slot = path->slots[0];
eb = path->nodes[0];
/* make sure we can use eb after releasing the path */
- if (eb != eb_in)
+ if (eb != eb_in) {
atomic_inc(&eb->refs);
+ btrfs_tree_read_lock(eb);
+ btrfs_set_lock_blocking_rw(eb, BTRFS_READ_LOCK);
+ }
btrfs_release_path(path);
iref = btrfs_item_ptr(eb, slot, struct btrfs_inode_ref);
@@ -931,6 +939,7 @@
}
btrfs_release_path(path);
+ path->leave_spinning = leave_spinning;
if (ret)
return ERR_PTR(ret);
@@ -1260,6 +1269,7 @@
struct btrfs_key found_key;
while (!ret) {
+ path->leave_spinning = 1;
ret = inode_ref_info(inum, parent ? parent+1 : 0, fs_root, path,
&found_key);
if (ret < 0)
@@ -1275,6 +1285,8 @@
eb = path->nodes[0];
/* make sure we can use eb after releasing the path */
atomic_inc(&eb->refs);
+ btrfs_tree_read_lock(eb);
+ btrfs_set_lock_blocking_rw(eb, BTRFS_READ_LOCK);
btrfs_release_path(path);
item = btrfs_item_nr(eb, slot);
@@ -1293,6 +1305,7 @@
len = sizeof(*iref) + name_len;
iref = (struct btrfs_inode_ref *)((char *)iref + len);
}
+ btrfs_tree_read_unlock_blocking(eb);
free_extent_buffer(eb);
}