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

[Chao Yu]

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