linux-kernel - [PATCH 2/2] f2fs: add __pack attribute for extent

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Message-ID: <20230331092658.72386-2-bo.ye@mediatek.com>
Date:   Fri, 31 Mar 2023 17:26:57 +0800
From:   Bo Ye <bo.ye@...iatek.com>
To:     Jaegeuk Kim <jaegeuk@...nel.org>, Chao Yu <chao@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        xiongping1 <xiongping1@...omi.com>,
        qixiaoyu1 <qixiaoyu1@...omi.com>
CC:     <yongdong.zhang@...iatek.com>, <peng.zhou@...iatek.com>,
        <browse.zhang@...iatek.com>, <light.hsieh@...iatek.com>,
        Qilin Tan <qilin.tan@...iatek.com>, Bo Ye <bo.ye@...iatek.com>,
        <linux-f2fs-devel@...ts.sourceforge.net>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-mediatek@...ts.infradead.org>
Subject: [PATCH 2/2] f2fs: add __pack attribute for extent_info

From: Qilin Tan <qilin.tan@...iatek.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@...iatek.com>
Signed-off-by: Qilin Tan <qilin.tan@...iatek.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