btrfs: fix race in reada
When inserting into the radix tree returns EEXIST, get the existing
entry without giving up the spinlock in between.
There was a race for both the zones trees and the extent tree.
Signed-off-by: Arne Jansen <sensille@gmx.net>
diff --git a/fs/btrfs/reada.c b/fs/btrfs/reada.c
index dc5d331..8dec650 100644
--- a/fs/btrfs/reada.c
+++ b/fs/btrfs/reada.c
@@ -250,14 +250,12 @@
struct btrfs_bio *bbio)
{
int ret;
- int looped = 0;
struct reada_zone *zone;
struct btrfs_block_group_cache *cache = NULL;
u64 start;
u64 end;
int i;
-again:
zone = NULL;
spin_lock(&fs_info->reada_lock);
ret = radix_tree_gang_lookup(&dev->reada_zones, (void **)&zone,
@@ -274,9 +272,6 @@
spin_unlock(&fs_info->reada_lock);
}
- if (looped)
- return NULL;
-
cache = btrfs_lookup_block_group(fs_info, logical);
if (!cache)
return NULL;
@@ -307,13 +302,15 @@
ret = radix_tree_insert(&dev->reada_zones,
(unsigned long)(zone->end >> PAGE_CACHE_SHIFT),
zone);
- spin_unlock(&fs_info->reada_lock);
- if (ret) {
+ if (ret == -EEXIST) {
kfree(zone);
- looped = 1;
- goto again;
+ ret = radix_tree_gang_lookup(&dev->reada_zones, (void **)&zone,
+ logical >> PAGE_CACHE_SHIFT, 1);
+ if (ret == 1)
+ kref_get(&zone->refcnt);
}
+ spin_unlock(&fs_info->reada_lock);
return zone;
}
@@ -323,8 +320,8 @@
struct btrfs_key *top, int level)
{
int ret;
- int looped = 0;
struct reada_extent *re = NULL;
+ struct reada_extent *re_exist = NULL;
struct btrfs_fs_info *fs_info = root->fs_info;
struct btrfs_mapping_tree *map_tree = &fs_info->mapping_tree;
struct btrfs_bio *bbio = NULL;
@@ -335,14 +332,13 @@
int i;
unsigned long index = logical >> PAGE_CACHE_SHIFT;
-again:
spin_lock(&fs_info->reada_lock);
re = radix_tree_lookup(&fs_info->reada_tree, index);
if (re)
kref_get(&re->refcnt);
spin_unlock(&fs_info->reada_lock);
- if (re || looped)
+ if (re)
return re;
re = kzalloc(sizeof(*re), GFP_NOFS);
@@ -398,12 +394,15 @@
/* insert extent in reada_tree + all per-device trees, all or nothing */
spin_lock(&fs_info->reada_lock);
ret = radix_tree_insert(&fs_info->reada_tree, index, re);
+ if (ret == -EEXIST) {
+ re_exist = radix_tree_lookup(&fs_info->reada_tree, index);
+ BUG_ON(!re_exist);
+ kref_get(&re_exist->refcnt);
+ spin_unlock(&fs_info->reada_lock);
+ goto error;
+ }
if (ret) {
spin_unlock(&fs_info->reada_lock);
- if (ret != -ENOMEM) {
- /* someone inserted the extent in the meantime */
- looped = 1;
- }
goto error;
}
for (i = 0; i < nzones; ++i) {
@@ -450,9 +449,7 @@
}
kfree(bbio);
kfree(re);
- if (looped)
- goto again;
- return NULL;
+ return re_exist;
}
static void reada_kref_dummy(struct kref *kr)