Re: [PATCH 1/2] btrfs-progs: check/original: detect directory inode with nlinks >= 2

[Su Yue <l@damenly.su>]

On Sun 18 Jul 2021 at 20:54, Qu Wenruo <wqu@suse.com> wrote:

> Linux VFS doesn't allow directory to have hard links, thus for 
> btrfs
> on-disk directory inode items, their nlinks should never go 
> beyond 1.
>
> Lowmem mode already has the check and will report it without 
> problem.
> Only original mode needs this update.
>
> Reported-by: Pepperpoint <pepperpoint@mb.ardentcoding.com>
> Link: 
> https://lore.kernel.org/linux-btrfs/162648632340.7.1932907459648384384.10178178@mb.ardentcoding.com/
> Signed-off-by: Qu Wenruo <wqu@suse.com>
>
Reviewed-by: Su Yue <l@damenly.su>

--
Su
> ---
>  check/main.c          | 7 +++++++
>  check/mode-original.h | 1 +
>  2 files changed, 8 insertions(+)
>
> diff --git a/check/main.c b/check/main.c
> index ee6cf793251c..df2303939ffe 100644
> --- a/check/main.c
> +++ b/check/main.c
> @@ -623,6 +623,9 @@ static void print_inode_error(struct 
> btrfs_root *root, struct inode_record *rec)
>  			rec->imode & ~07777);
>  	if (errors & I_ERR_INVALID_GEN)
>  		fprintf(stderr, ", invalid inode generation or transid");
> +	if (errors & I_ERR_INVALID_NLINK)
> +		fprintf(stderr, ", directory has invalid nlink %d",
> +			rec->nlink);
>  	fprintf(stderr, "\n");
>
>  	/* Print the holes if needed */
> @@ -909,6 +912,10 @@ static int process_inode_item(struct 
> extent_buffer *eb,
>  	if (S_ISLNK(rec->imode) &&
>  	    flags & (BTRFS_INODE_IMMUTABLE | BTRFS_INODE_APPEND))
>  		rec->errors |= I_ERR_ODD_INODE_FLAGS;
> +
> +	/* Directory should never have hard link */
> +	if (S_ISDIR(rec->imode) && rec->nlink >= 2)
> +		rec->errors |= I_ERR_INVALID_NLINK;
>  	/*
>  	 * We don't have accurate root info to determine the correct
>  	 * inode generation uplimit, use super_generation + 1 anyway
> diff --git a/check/mode-original.h b/check/mode-original.h
> index b075a95c9757..eed16d92d0db 100644
> --- a/check/mode-original.h
> +++ b/check/mode-original.h
> @@ -186,6 +186,7 @@ struct unaligned_extent_rec_t {
>  #define I_ERR_MISMATCH_DIR_HASH		(1 << 18)
>  #define I_ERR_INVALID_IMODE		(1 << 19)
>  #define I_ERR_INVALID_GEN		(1 << 20)
> +#define I_ERR_INVALID_NLINK		(1 << 21)
>
>  struct inode_record {
>  	struct list_head backrefs;