Re: [PATCH] ext4: fix reserved space counter leakage
From: Eric Whitney <hidden>
Date: 2021-08-20 16:46:02
* Jeffle Xu [off-list ref]:
When ext4_es_insert_delayed_block() returns error, e.g., ENOMEM, previously reserved space is not released as the error handling, in which case @s_dirtyclusters_counter is left over. Since this delayed extent failes to be inserted into extent status tree, when inode is written back, the extra @s_dirtyclusters_counter won't be subtracted and remains there forever. This can leads to /sys/fs/ext4/<dev>/delayed_allocation_blocks remains non-zero even when syncfs is executed on the filesystem.
Hi: I think the fix below looks fine. However, this comment doesn't look right to me. Are you really seeing delayed_allocation_blocks values that remain incorrectly elevated across last closes (or across file system unmounts and remounts)? s_dirtyclusters_counter isn't written out to stable storage - it's an in-memory only variable that's created when a file is first opened and destroyed on last close. Eric
quoted hunk ↗ jump to hunk
Fixes: 51865fda28e5 ("ext4: let ext4 maintain extent status tree") Cc: <redacted> Reported-by: Gao Xiang <redacted> Signed-off-by: Jeffle Xu <jefflexu@linux.alibaba.com> --- fs/ext4/inode.c | 5 +++++ 1 file changed, 5 insertions(+)diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 82087657860b..7f15da370281 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c@@ -1650,6 +1650,7 @@ static int ext4_insert_delayed_block(struct inode *inode, ext4_lblk_t lblk) struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb); int ret; bool allocated = false; + bool reserved = false; /* * If the cluster containing lblk is shared with a delayed,@@ -1666,6 +1667,7 @@ static int ext4_insert_delayed_block(struct inode *inode, ext4_lblk_t lblk) ret = ext4_da_reserve_space(inode); if (ret != 0) /* ENOSPC */ goto errout; + reserved = true; } else { /* bigalloc */ if (!ext4_es_scan_clu(inode, &ext4_es_is_delonly, lblk)) { if (!ext4_es_scan_clu(inode,@@ -1678,6 +1680,7 @@ static int ext4_insert_delayed_block(struct inode *inode, ext4_lblk_t lblk) ret = ext4_da_reserve_space(inode); if (ret != 0) /* ENOSPC */ goto errout; + reserved = true; } else { allocated = true; }@@ -1688,6 +1691,8 @@ static int ext4_insert_delayed_block(struct inode *inode, ext4_lblk_t lblk) } ret = ext4_es_insert_delayed_block(inode, lblk, allocated); + if (ret && reserved) + ext4_da_release_space(inode, 1); errout: return ret;-- 2.27.0