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Date:   Thu, 4 Jun 2020 13:31:40 -0600
From:   Andreas Dilger <adilger@...ger.ca>
To:     Chengguang Xu <cgxu519@...ernel.net>
Cc:     jack@...e.com, linux-ext4@...r.kernel.org
Subject: Re: [RFC PATCH] ext2: drop cached block when detecting corruption

On Jun 3, 2020, at 03:44, Chengguang Xu <cgxu519@...ernel.net> wrote:
> 
> ´╗┐Currently ext2 uses mdcache for deduplication of extended

(typo) this should be "mbcache"


> attribution blocks. However, there is lack of handling for
> corrupted blocks, so newly created EAs may still links to
> corrupted blocks. This patch tries to drop cached block
> when detecting corruption to mitigate the effect.
> 
> Signed-off-by: Chengguang Xu <cgxu519@...ernel.net>
> ---
> fs/ext2/xattr.c | 25 ++++++++++++++++++++++---
> 1 file changed, 22 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/ext2/xattr.c b/fs/ext2/xattr.c
> index 943cc469f42f..969521e39753 100644
> --- a/fs/ext2/xattr.c
> +++ b/fs/ext2/xattr.c
> @@ -93,6 +93,8 @@ static int ext2_xattr_set2(struct inode *, struct buffer_head *,
>               struct ext2_xattr_header *);
> 
> static int ext2_xattr_cache_insert(struct mb_cache *, struct buffer_head *);
> +static void ext2_xattr_cache_remove(struct mb_cache *cache,
> +                    struct buffer_head *bh);
> static struct buffer_head *ext2_xattr_cache_find(struct inode *,
>                         struct ext2_xattr_header *);
> static void ext2_xattr_rehash(struct ext2_xattr_header *,
> @@ -237,8 +239,10 @@ ext2_xattr_get(struct inode *inode, int name_index, const char *name,
>    entry = FIRST_ENTRY(bh);
>    while (!IS_LAST_ENTRY(entry)) {
>        if (!ext2_xattr_entry_valid(entry, end,
> -            inode->i_sb->s_blocksize))
> +            inode->i_sb->s_blocksize)) {
> +            ext2_xattr_cache_remove(ea_block_cache, bh);
>            goto bad_block;
> +        }
> 
>        not_found = ext2_xattr_cmp_entry(name_index, name_len, name,
>                         entry);
> @@ -323,8 +327,10 @@ ext2_xattr_list(struct dentry *dentry, char *buffer, size_t buffer_size)
>    entry = FIRST_ENTRY(bh);
>    while (!IS_LAST_ENTRY(entry)) {
>        if (!ext2_xattr_entry_valid(entry, end,
> -            inode->i_sb->s_blocksize))
> +            inode->i_sb->s_blocksize)) {
> +            ext2_xattr_cache_remove(ea_block_cache, bh);
>            goto bad_block;
> +        }
>        entry = EXT2_XATTR_NEXT(entry);
>    }
>    if (ext2_xattr_cache_insert(ea_block_cache, bh))
> @@ -407,6 +413,7 @@ int
> ext2_xattr_set(struct inode *inode, int name_index, const char *name,
>           const void *value, size_t value_len, int flags)
> {
> +    struct mb_cache *ea_block_cache = EA_BLOCK_CACHE(inode);
>    struct super_block *sb = inode->i_sb;
>    struct buffer_head *bh = NULL;
>    struct ext2_xattr_header *header = NULL;
> @@ -464,8 +471,11 @@ ext2_xattr_set(struct inode *inode, int name_index, const char *name,
>         */
>        last = FIRST_ENTRY(bh);
>        while (!IS_LAST_ENTRY(last)) {
> -            if (!ext2_xattr_entry_valid(last, end, sb->s_blocksize))
> +            if (!ext2_xattr_entry_valid(last, end,
> +                sb->s_blocksize)) {
> +                ext2_xattr_cache_remove(ea_block_cache, bh);
>                goto bad_block;
> +            }
>            if (last->e_value_size) {
>                size_t offs = le16_to_cpu(last->e_value_offs);
>                if (offs < min_offs)
> @@ -881,6 +891,15 @@ ext2_xattr_cache_insert(struct mb_cache *cache, struct buffer_head *bh)
>    return error;
> }
> 
> +static void
> +ext2_xattr_cache_remove(struct mb_cache *cache, struct buffer_head *bh)
> +{
> +    lock_buffer(bh);
> +    mb_cache_entry_delete(cache, le32_to_cpu(HDR(bh)->h_hash),
> +                  bh->b_blocknr);
> +    unlock_buffer(bh);
> +}
> +
> /*
>  * ext2_xattr_cmp()
>  *
> -- 
> 2.20.1
> 
> 

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