Re: [PATCH] f2fs: fix unaligned field offset in 32-bits platform

[Chao Yu]

On 2023/3/8 1:26, Jaegeuk Kim wrote:
> Cc'ed stable. Thanks.

Oh, thanks for adding the missed tag! Jaegeuk.

Thanks,

> On 03/07, Chao Yu wrote:
> > F2FS-fs (dm-x): inconsistent rbtree, cur(3470333575168) next(3320009719808)
> > ------------[ cut here ]------------
> > kernel BUG at fs/f2fs/gc.c:602!
> > Internal error: Oops - BUG: 0 [#1] PREEMPT SMP ARM
> > PC is at get_victim_by_default+0x13c0/0x1498
> > LR is at f2fs_check_rb_tree_consistence+0xc4/0xd4
> > ....
> > [<c04d98b0>] (get_victim_by_default) from [<c04d4f44>] (f2fs_gc+0x220/0x6cc)
> > [<c04d4f44>] (f2fs_gc) from [<c04d4780>] (gc_thread_func+0x2ac/0x708)
> > [<c04d4780>] (gc_thread_func) from [<c015c774>] (kthread+0x1a8/0x1b4)
> > [<c015c774>] (kthread) from [<c01010b4>] (ret_from_fork+0x14/0x20)
> >
> > The reason is there is __packed attribute in struct rb_entry, but there
> > is no __packed attribute in struct victim_entry, so wrong offset of key
> > field will be parsed in struct rb_entry in f2fs_check_rb_tree_consistence,
> > it describes memory layouts of struct rb_entry and struct victim_entry in
> > 32-bits platform as below:
> >
> > struct rb_entry {
> >     [0] struct rb_node rb_node;
> >         union {
> >             struct {...};
> >    [12]     unsigned long long key;
> >         } __packed;
> > }
> > size of struct rb_entry: 20
> >
> > struct victim_entry {
> >     [0] struct rb_node rb_node;
> >         union {
> >             struct {...};
> >    [16]     struct victim_info vi;
> >         };
> >    [32] struct list_head list;
> > }
> > size of struct victim_entry: 40
> >
> > This patch tries to add __packed attribute in below structure:
> > - discard_info, discard_cmd
> > - extent_info, extent_node
> > - victim_info, victim_entry
> > in order to fix this unaligned field offset issue in 32-bits platform.
> >
> > Fixes: 004b68621897 ("f2fs: use rb-tree to track pending discard commands")
> > Fixes: 13054c548a1c ("f2fs: introduce infra macro and data structure of rb-tree extent cache")
> > Fixes: 093749e296e2 ("f2fs: support age threshold based garbage collection")
> > Signed-off-by: Zhiguo Niu <zhiguo.niu@xxxxxxxxxx>
> > Signed-off-by: Chao Yu <chao@xxxxxxxxxx>
> > ---
> >   fs/f2fs/f2fs.h | 6 +++---
> >   fs/f2fs/gc.h   | 4 ++--
> >   2 files changed, 5 insertions(+), 5 deletions(-)
> >
> > diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> > index b0ab2062038a..17fa7572ceed 100644
> > --- a/fs/f2fs/f2fs.h
> > +++ b/fs/f2fs/f2fs.h
> > @@ -349,7 +349,7 @@ struct discard_info {
> >   	block_t lstart;			/* logical start address */
> >   	block_t len;			/* length */
> >   	block_t start;			/* actual start address in dev */
> > -};
> > +} __packed;
> >   
> >   struct discard_cmd {
> >   	struct rb_node rb_node;		/* rb node located in rb-tree */
> > @@ -361,7 +361,7 @@ struct discard_cmd {
> >   		};
> >   		struct discard_info di;	/* discard info */
> >   
> > -	};
> > +	} __packed;
> >   	struct list_head list;		/* command list */
> >   	struct completion wait;		/* compleation */
> >   	struct block_device *bdev;	/* bdev */
> > @@ -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 */
> > diff --git a/fs/f2fs/gc.h b/fs/f2fs/gc.h
> > index 15bd1d680f67..304937d9a084 100644
> > --- a/fs/f2fs/gc.h
> > +++ b/fs/f2fs/gc.h
> > @@ -58,7 +58,7 @@ struct gc_inode_list {
> >   struct victim_info {
> >   	unsigned long long mtime;	/* mtime of section */
> >   	unsigned int segno;		/* section No. */
> > -};
> > +} __packed;
> >   
> >   struct victim_entry {
> >   	struct rb_node rb_node;		/* rb node located in rb-tree */
> > @@ -68,7 +68,7 @@ struct victim_entry {
> >   			unsigned int segno;		/* segment No. */
> >   		};
> >   		struct victim_info vi;	/* victim info */
> > -	};
> > +	} __packed;
> >   	struct list_head list;
> >   };
> >   
> > --
> > 2.36.1