hulk inclusion category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/I9DN5Z CVE: NA
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ext4 only reserved space for delalloc for data blocks, doesn't reserve space for metadata blocks in ext4_da_reserve_space(). Besides, if we enable dioread_nolock mount option, it also doesn't reserve metadata blocks for the extent status conversion.
In order to prevent data loss caused by fail to allocate metadata blocks on writeback, we reserve 2% space or 4096 blocks for meta data, and use EXT4_GET_BLOCKS_PRE_IO to do the potential split in advance. But all these two methods were just best efforts, if it's really running out of sapce, there is no difference between splitting extent on writeback and on IO completed, both will lead to data loss.
The best way is to reserve enough space for metadata. Before that, we can at least make sure that things won't get worse if we postpone splitting extent to endio. So let's use reserved sapce in endio too.
Signed-off-by: Zhang Yi yi.zhang@huawei.com --- fs/ext4/extents.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c index ed65ae462210..a3eb1465d3c2 100644 --- a/fs/ext4/extents.c +++ b/fs/ext4/extents.c @@ -3733,7 +3733,8 @@ static int ext4_convert_unwritten_extents_endio(handle_t *handle, (unsigned long long)map->m_lblk, map->m_len); #endif err = ext4_split_convert_extents(handle, inode, map, ppath, - EXT4_GET_BLOCKS_CONVERT); + EXT4_GET_BLOCKS_CONVERT | + EXT4_GET_BLOCKS_METADATA_NOFAIL); if (err < 0) return err; path = ext4_find_extent(inode, map->m_lblk, ppath, 0);