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

[Bo Ye <bo.ye@mediatek.com>]

From: Qilin Tan <qilin.tan@mediatek.com>

Need add __pack for struct extent_info to align to memory
layout of struct rb_entry.

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 */
-- 
2.17.0