From: Zhang Yi <yi.zhang@xxxxxxxxxx>
In ext4_map_blocks(), if we can't find a range of mapping in the
extents cache, we are calling ext4_ext_map_blocks() to search the real
path. But if the querying range was tail overlaped by a delayed extent,
we can't find it on the real extent path, so the returned hole length
could be larger than it really is.
| querying map |
v v
|----------{-------------}{------|----------------}-----...
^ ^ ^^ ^
| uncached | hole extent || delayed extent |
We have to adjust the mapping length to the next not hole extent's
lblk before searching the extent path.
Signed-off-by: Zhang Yi <yi.zhang@xxxxxxxxxx>
---
fs/ext4/inode.c | 24 ++++++++++++++++++++++--
1 file changed, 22 insertions(+), 2 deletions(-)
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 4ce35f1c8b0a..94e7b8500878 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -479,6 +479,7 @@ int ext4_map_blocks(handle_t *handle, struct inode *inode,
struct ext4_map_blocks *map, int flags)
{
struct extent_status es;
+ ext4_lblk_t next;
int retval;
int ret = 0;
#ifdef ES_AGGRESSIVE_TEST
@@ -502,8 +503,10 @@ int ext4_map_blocks(handle_t *handle, struct inode *inode,
return -EFSCORRUPTED;
/* Lookup extent status tree firstly */
- if (!(EXT4_SB(inode->i_sb)->s_mount_state & EXT4_FC_REPLAY) &&
- ext4_es_lookup_extent(inode, map->m_lblk, NULL, &es)) {
+ if (EXT4_SB(inode->i_sb)->s_mount_state & EXT4_FC_REPLAY)
+ goto uncached;
+
+ if (ext4_es_lookup_extent(inode, map->m_lblk, NULL, &es)) {
if (ext4_es_is_written(&es) || ext4_es_is_unwritten(&es)) {
map->m_pblk = ext4_es_pblock(&es) +
map->m_lblk - es.es_lblk;
@@ -532,6 +535,23 @@ int ext4_map_blocks(handle_t *handle, struct inode *inode,
#endif
goto found;
}
+ /*
+ * Not found, maybe a hole, need to adjust the map length before
+ * seraching the real extent path. It can prevent incorrect hole
+ * length returned if the following entries have delayed only
+ * ones.
+ */
+ if (!(flags & EXT4_GET_BLOCKS_CREATE) && es.es_lblk > map->m_lblk) {
+ next = es.es_lblk;
+ if (ext4_es_is_hole(&es))
+ next = ext4_es_skip_hole_extent(inode, map->m_lblk,
+ map->m_len);
+ retval = next - map->m_lblk;
+ if (map->m_len > retval)
+ map->m_len = retval;
+ }
+
+uncached:
/*
* In the query cache no-wait mode, nothing we can do more if we
* cannot find extent in the cache.
--
2.39.2
