Re: [PATCH 2/2] f2fs: add __pack attribute for extent_info

["Bo Ye (叶波)" <Bo.Ye@mediatek.com>]

On Sat, 2023-04-01 at 09:00 +0800, Chao Yu wrote:
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> 
> On 2023/3/31 17:26, Bo Ye wrote:
> > From: Qilin Tan <qilin.tan@mediatek.com>
> > 
> > Need add __pack for struct extent_info to align to memory
> > layout of struct rb_entry.
> 
> Jaegeuk has fixed this bug w/ below patchset, please check it:
> 
> 
https://lore.kernel.org/linux-f2fs-devel/20230313201216.924234-1-jaegeuk@kernel.org/
> 
> Thanks,
> 
  OK, under verifying, I will reply with test result. 
  Thanks a lot!
> > 
> > struct rb_entry {
> >      struct rb_node rb_node;     /* rb node located in rb-tree */
> >      union {
> >          struct {
> >              unsigned int ofs;   /* start offset of the entry */
> >              unsigned int len;   /* length of the entry */
> >          };
> >          unsigned long long key;     /* 64-bits key */
> >      } __packed;
> > };
> > 
> > struct extent_info {
> >      unsigned int fofs;      /* start offset in a file */
> >      unsigned int len;       /* length of the extent */
> >      union {
> >          ...
> >          /* block age extent_cache */
> >          struct {
> >              /* block age of the extent */
> >              unsigned long long age;
> >              /* last total blocks allocated */
> >              unsigned long long last_blocks;
> >          };
> > };
> > 
> > The new fields(age, last_blocks) are u64 in change 71644dff4811, it
> > cause the memory alignment based on 8 bytes in some complier. So
> > the
> > field fofs and len are alloced with 8 bytes and using the last 4
> > byts.
> > Its memory is not aligned with struct rb_entry. the ofs of rb_entry
> > pointer to a invalid value and cause writing file failed.
> > 
> > struct extent_info's offset should be 12 rather than 16 from the
> > beginning of struct rb_entry.
> > 
> > The offset dump for the bad case as:
> > kworker/u16:6:
> > [name:f2fs&]f2fs_lookup_rb_tree_for_insert:MTK_DEBUG: ino=1629
> > re=0xc675dc08 ofs=0 re->ofs=0, re->len=68 ei=0xc675dc18 ei.fofs=68
> > ei.len=277
> > 
> > Fixes: 71644dff4811 ("f2fs: add block_age-based extent cache")
> > Signed-off-by: Bo Ye <bo.ye@mediatek.com>
> > Signed-off-by: Qilin Tan <qilin.tan@mediatek.com>
> > ---
> >   fs/f2fs/f2fs.h | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> > index b0ab2062038a..7c690667a42f 100644
> > --- a/fs/f2fs/f2fs.h
> > +++ b/fs/f2fs/f2fs.h
> > @@ -660,7 +660,7 @@ struct extent_info {
> >                       unsigned long long last_blocks;
> >               };
> >       };
> > -};
> > +} __packed;
> > 
> >   struct extent_node {
> >       struct rb_node rb_node;         /* rb node located in rb-tree 
> > */