Btrfs: Fix bookend extent race v2
When dropping middle part of an extent, btrfs_drop_extents truncates
the extent at first, then inserts a bookend extent.
Since truncation and insertion can't be done atomically, there is a small
period that the bookend extent isn't in the tree. This causes problem for
functions that search the tree for file extent item. The way to fix this is
lock the range of the bookend extent before truncation.
Signed-off-by: Yan Zheng <zheng.yan@oracle.com>
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index fada9c2..535cee47 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -3379,11 +3379,13 @@
struct btrfs_root *root = BTRFS_I(reloc_inode)->root;
struct extent_map_tree *em_tree = &BTRFS_I(reloc_inode)->extent_tree;
struct extent_map *em;
+ u64 start = extent_key->objectid - offset;
+ u64 end = start + extent_key->offset - 1;
em = alloc_extent_map(GFP_NOFS);
BUG_ON(!em || IS_ERR(em));
- em->start = extent_key->objectid - offset;
+ em->start = start;
em->len = extent_key->offset;
em->block_len = extent_key->offset;
em->block_start = extent_key->objectid;
@@ -3391,7 +3393,7 @@
set_bit(EXTENT_FLAG_PINNED, &em->flags);
/* setup extent map to cheat btrfs_readpage */
- mutex_lock(&BTRFS_I(reloc_inode)->extent_mutex);
+ lock_extent(&BTRFS_I(reloc_inode)->io_tree, start, end, GFP_NOFS);
while (1) {
int ret;
spin_lock(&em_tree->lock);
@@ -3401,13 +3403,11 @@
free_extent_map(em);
break;
}
- btrfs_drop_extent_cache(reloc_inode, em->start,
- em->start + em->len - 1, 0);
+ btrfs_drop_extent_cache(reloc_inode, start, end, 0);
}
- mutex_unlock(&BTRFS_I(reloc_inode)->extent_mutex);
+ unlock_extent(&BTRFS_I(reloc_inode)->io_tree, start, end, GFP_NOFS);
- return relocate_inode_pages(reloc_inode, extent_key->objectid - offset,
- extent_key->offset);
+ return relocate_inode_pages(reloc_inode, start, extent_key->offset);
}
struct btrfs_ref_path {
@@ -3831,7 +3831,6 @@
* the file extent item was modified by someone
* before the extent got locked.
*/
- mutex_unlock(&BTRFS_I(inode)->extent_mutex);
unlock_extent(&BTRFS_I(inode)->io_tree, lock_start,
lock_end, GFP_NOFS);
extent_locked = 0;
@@ -3896,8 +3895,12 @@
lock_start = key.offset;
lock_end = lock_start + num_bytes - 1;
} else {
- BUG_ON(lock_start != key.offset);
- BUG_ON(lock_end - lock_start + 1 < num_bytes);
+ if (lock_start > key.offset ||
+ lock_end + 1 < key.offset + num_bytes) {
+ unlock_extent(&BTRFS_I(inode)->io_tree,
+ lock_start, lock_end, GFP_NOFS);
+ extent_locked = 0;
+ }
}
if (!inode) {
@@ -3951,7 +3954,6 @@
if (ordered)
btrfs_put_ordered_extent(ordered);
- mutex_lock(&BTRFS_I(inode)->extent_mutex);
extent_locked = 1;
continue;
}
@@ -4073,7 +4075,6 @@
}
if (extent_locked) {
- mutex_unlock(&BTRFS_I(inode)->extent_mutex);
unlock_extent(&BTRFS_I(inode)->io_tree, lock_start,
lock_end, GFP_NOFS);
extent_locked = 0;
@@ -4091,7 +4092,6 @@
if (inode) {
mutex_unlock(&inode->i_mutex);
if (extent_locked) {
- mutex_unlock(&BTRFS_I(inode)->extent_mutex);
unlock_extent(&BTRFS_I(inode)->io_tree, lock_start,
lock_end, GFP_NOFS);
}
@@ -4180,10 +4180,8 @@
lock_extent(&BTRFS_I(inode)->io_tree, key.offset,
key.offset + num_bytes - 1, GFP_NOFS);
- mutex_lock(&BTRFS_I(inode)->extent_mutex);
btrfs_drop_extent_cache(inode, key.offset,
key.offset + num_bytes - 1, 1);
- mutex_unlock(&BTRFS_I(inode)->extent_mutex);
unlock_extent(&BTRFS_I(inode)->io_tree, key.offset,
key.offset + num_bytes - 1, GFP_NOFS);
cond_resched();