From: Robin Dong <sanbai@xxxxxxxxxx>
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@xxxxxxxxxx>
---
fs/ext4/mballoc.c | 5 +++++
1 files changed, 5 insertions(+), 0 deletions(-)
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 17a5a57..6b58247 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -3969,6 +3969,11 @@ static void ext4_mb_group_or_file(struct ext4_allocation_context *ac)
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) {
--
1.7.4.1
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