Re: [f2fs-dev] [PATCH v3 3/6] f2fs: compress: fix to check unreleased compressed cluster

[Daeho Jeong]

On Wed, Jan 10, 2024 at 5:33 PM Chao Yu <chao@xxxxxxxxxx> wrote:
>
> On 2024/1/11 9:18, Daeho Jeong wrote:
> > On Thu, Dec 28, 2023 at 6:33 AM Chao Yu <chao@xxxxxxxxxx> wrote:
> >>
> >> From: Sheng Yong <shengyong@xxxxxxxx>
> >>
> >> Compressed cluster may not be released due to we can fail in
> >> release_compress_blocks(), fix to handle reserved compressed
> >> cluster correctly in reserve_compress_blocks().
> >>
> >> Fixes: 4c8ff7095bef ("f2fs: support data compression")
> >> Signed-off-by: Sheng Yong <shengyong@xxxxxxxx>
> >> Signed-off-by: Chao Yu <chao@xxxxxxxxxx>
> >> ---
> >>   fs/f2fs/file.c | 12 ++++++++++++
> >>   1 file changed, 12 insertions(+)
> >>
> >> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> >> index 026d05a7edd8..782ae3be48f6 100644
> >> --- a/fs/f2fs/file.c
> >> +++ b/fs/f2fs/file.c
> >> @@ -3624,6 +3624,15 @@ static int reserve_compress_blocks(struct dnode_of_data *dn, pgoff_t count)
> >>                                  goto next;
> >>                          }
> >>
> >> +                       /*
> >> +                        * compressed cluster was not released due to
> >> +                        * it fails in release_compress_blocks().
> >> +                        */
> >> +                       if (blkaddr == NEW_ADDR) {
> >> +                               compr_blocks++;
> >> +                               continue;
> >> +                       }
> >> +
> >>                          if (__is_valid_data_blkaddr(blkaddr)) {
> >>                                  compr_blocks++;
> >>                                  continue;
> >
> > How about merging two conditions like "blkaddr == NEW_ADDR ||
> > __is_valid_data_blkaddr(blkaddr)"?
>
> Oh, sure.
>
> >
> >> @@ -3633,6 +3642,9 @@ static int reserve_compress_blocks(struct dnode_of_data *dn, pgoff_t count)
> >>                  }
> >>
> >>                  reserved = cluster_size - compr_blocks;
> >> +               if (!reserved)
> >> +                       goto next;
> >> +
> >
> > How can the reserved variable be zero?
>
> I guess it can happen if a cluster was not released during
> release_compress_blocks(), then all blocks in the cluster should
> has been reserved, so, in this round of reserving, it needs to skip
> reserve blocks, right?

Let's assume cluster_size is 4. How can compr_blocks be 4?

                        if (i == 0) {
                                if (blkaddr == COMPRESS_ADDR)
                                        continue;
                                dn->ofs_in_node += cluster_size;
                                goto next;
                        }

We skip the block having COMPRESS_ADDR when counting compr_blocks.
So, the maximum value of compr_blocks should be 3, right?

>
> Thanks,
>
> >
> >>                  ret = inc_valid_block_count(sbi, dn->inode, &reserved);
> >>                  if (ret)
> >>                          return ret;
> >> --
> >> 2.40.1
> >>
> >>
> >>
> >> _______________________________________________
> >> Linux-f2fs-devel mailing list
> >> Linux-f2fs-devel@xxxxxxxxxxxxxxxxxxxxx
> >> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel