On Fri, Aug 20, 2021 at 12:45:56PM -0400, Eric Whitney wrote:
> * Jeffle Xu <jefflexu@xxxxxxxxxxxxxxxxx>:
> > 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.
hmmm.... Let me explain a bit about this. It can be reproduced easily by fault
injection with the code modified below:
diff --git a/fs/ext4/extents_status.c b/fs/ext4/extents_status.c
index 9a3a8996aacf..29dc0da5960c 100644
--- a/fs/ext4/extents_status.c
+++ b/fs/ext4/extents_status.c
@@ -794,6 +794,9 @@ static int __es_insert_extent(struct inode *inode, struct extent_status *newes)
}
}
+ if (!(ktime_get_ns() % 3)) {
+ return -ENOMEM;
+ }
es = ext4_es_alloc_extent(inode, newes->es_lblk, newes->es_len,
newes->es_pblk);
if (!es)
and then run a loop
while true; do dd if=/dev/zero of=aaa bs=8192 count=10000; sync; rm -rf aaa; done
After "Cannot allocate memory reported" is shown, s_dirtyclusters_counter
was already leaked. It can cause df and free space counting incorrect in
this mount.
If my understanging is correct, in priciple, we should also check with
"WARN_ON(ei->i_reserved_data_blocks)" in the inode evict path since it
should be considered as 0.
Thanks,
Gao Xiang
>
> Eric
>
> > Fixes: 51865fda28e5 ("ext4: let ext4 maintain extent status tree")
> > Cc: <stable@xxxxxxxxxxxxxxx>
> > Reported-by: Gao Xiang <hsiangkao@xxxxxxxxxxxxxxxxx>
> > Signed-off-by: Jeffle Xu <jefflexu@xxxxxxxxxxxxxxxxx>
> > ---
> > 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
> >
