ext4: use stream-alloc when mb_group_prealloc set to zero
The kernel will crash on
ext4_mb_mark_diskspace_used:
BUG_ON(ac->ac_b_ex.fe_len <= 0);
after we set /sys/fs/ext4/sda/mb_group_prealloc to zero and create new files in an ext4 filesystem.
The reason is: ac_b_ex.fe_len also set to zero(mb_group_prealloc) in ext4_mb_normalize_group_request
because the ac_flags contains EXT4_MB_HINT_GROUP_ALLOC.
I think when someone set mb_group_prealloc to zero, it means DO NOT USE GROUP PREALLOCATION,
so we should set alloc-strategy to STREAM in this case.
Signed-off-by: Robin Dong <sanbai@taobao.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index cd70b30..8976265 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -4006,6 +4006,11 @@
return;
}
+ if (sbi->s_mb_group_prealloc <= 0) {
+ ac->ac_flags |= EXT4_MB_STREAM_ALLOC;
+ return;
+ }
+
/* don't use group allocation for large files */
size = max(size, isize);
if (size > sbi->s_mb_stream_request) {