ping? thanks, liubo On Wed, Oct 31, 2018 at 6:57 PM Liu Bo <bo.liu@xxxxxxxxxxxxxxxxx> wrote: > > With dioread_nolock, unwritten extents are converted in IO completion, and > these extents may be merged with siblings. > > ext4_writepages() has reserved a handle to hold 2 credits for inode update > and extent update and the handle will be used in IO completion as we can't > start journal after clearing PageWriteback (due to locking rules). > > However, if quota is enabled, the following enospc situation could happen, > > ext4_convert_unwritten_extents > ext4_ext_try_to_merge > ext4_ext_try_to_merge_up > ext4_journal_extend(handle, 2) # extend 2 credits for > # bitmap/group_desc > ext4_free_blocks() > dquot_free_block > // use 3 credits for 3 quota types > // use 1 credit for inode update > # update bitmap block > # update group desc block > # either of two updates may hit enospc > # as ->h_buffer_credits has been consumed out. > > In ext4_ext_try_to_merge(), per-inode extent tree may be collasped into > inode and ext4_free_blocks() will then free the unneeded blocks, but with > quota being enabled, there aren't enough credits to process updates and we > end up with -ENOSPC. > > As this is a corner case, instead of adding credits in ext4_writepages(), > this just extends more credits for quota when doing merge-up. > > Fixes: ecb94f5fdf4b (ext4: collapse a single extent tree block into the inode if possible) > CC: stable@xxxxxxxxxxxxxxx # v3.6-rc1+ > Signed-off-by: Liu Bo <bo.liu@xxxxxxxxxxxxxxxxx> > --- > fs/ext4/extents.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) > > diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c > index 240b6dea5441..ff2498355e3c 100644 > --- a/fs/ext4/extents.c > +++ b/fs/ext4/extents.c > @@ -1812,6 +1812,7 @@ static void ext4_ext_try_to_merge_up(handle_t *handle, > size_t s; > unsigned max_root = ext4_ext_space_root(inode, 0); > ext4_fsblk_t blk; > + int credits = 2; > > if ((path[0].p_depth != 1) || > (le16_to_cpu(path[0].p_hdr->eh_entries) != 1) || > @@ -1820,10 +1821,12 @@ static void ext4_ext_try_to_merge_up(handle_t *handle, > > /* > * We need to modify the block allocation bitmap and the block > - * group descriptor to release the extent tree block. If we > + * group descriptor to release the extent tree block. If > + * quota is enabled, updates on quota are also needed. If we > * can't get the journal credits, give up. > */ > - if (ext4_journal_extend(handle, 2)) > + credits += EXT4_MAXQUOTAS_TRANS_BLOCKS(inode->i_sb); > + if (ext4_journal_extend(handle, credits)) > return; > > /* > -- > 1.8.3.1 >
