On Wed, Aug 30, 2023 at 04:25:29PM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <djwong@xxxxxxxxxx>
>
> Create an expert-mode debugger command to create unlinked inodes.
> This will hopefully aid in simulation of leaked unlinked inode handling
> in the kernel and elsewhere.
>
> Signed-off-by: Darrick J. Wong <djwong@xxxxxxxxxx>
Reviewed-by: Bill O'Donnell <bodonnel@xxxxxxxxxx>
> ---
> db/iunlink.c | 196 ++++++++++++++++++++++++++++++++++++++++++++++
> libxfs/libxfs_api_defs.h | 1
> man/man8/xfs_db.8 | 11 +++
> 3 files changed, 208 insertions(+)
>
> diff --git a/db/iunlink.c b/db/iunlink.c
> index 303b5daf..d87562e3 100644
> --- a/db/iunlink.c
> +++ b/db/iunlink.c
> @@ -197,8 +197,204 @@ static const cmdinfo_t dump_iunlinked_cmd =
> N_("[-a agno] [-b bucket] [-q] [-v]"),
> N_("dump chain of unlinked inode buckets"), NULL };
>
> +/*
> + * Look up the inode cluster buffer and log the on-disk unlinked inode change
> + * we need to make.
> + */
> +static int
> +iunlink_log_dinode(
> + struct xfs_trans *tp,
> + struct xfs_inode *ip,
> + struct xfs_perag *pag,
> + xfs_agino_t next_agino)
> +{
> + struct xfs_mount *mp = tp->t_mountp;
> + struct xfs_dinode *dip;
> + struct xfs_buf *ibp;
> + int offset;
> + int error;
> +
> + error = -libxfs_imap_to_bp(mp, tp, &ip->i_imap, &ibp);
> + if (error)
> + return error;
> +
> + dip = xfs_buf_offset(ibp, ip->i_imap.im_boffset);
> +
> + dip->di_next_unlinked = cpu_to_be32(next_agino);
> + offset = ip->i_imap.im_boffset +
> + offsetof(struct xfs_dinode, di_next_unlinked);
> +
> + libxfs_dinode_calc_crc(mp, dip);
> + libxfs_trans_log_buf(tp, ibp, offset, offset + sizeof(xfs_agino_t) - 1);
> + return 0;
> +}
> +
> +static int
> +iunlink_insert_inode(
> + struct xfs_trans *tp,
> + struct xfs_perag *pag,
> + struct xfs_buf *agibp,
> + struct xfs_inode *ip)
> +{
> + struct xfs_mount *mp = tp->t_mountp;
> + struct xfs_agi *agi = agibp->b_addr;
> + xfs_agino_t next_agino;
> + xfs_agino_t agino = XFS_INO_TO_AGINO(mp, ip->i_ino);
> + short bucket_index = agino % XFS_AGI_UNLINKED_BUCKETS;
> + int offset;
> + int error;
> +
> + /*
> + * Get the index into the agi hash table for the list this inode will
> + * go on. Make sure the pointer isn't garbage and that this inode
> + * isn't already on the list.
> + */
> + next_agino = be32_to_cpu(agi->agi_unlinked[bucket_index]);
> + if (next_agino == agino || !xfs_verify_agino_or_null(pag, next_agino))
> + return EFSCORRUPTED;
> +
> + if (next_agino != NULLAGINO) {
> + /*
> + * There is already another inode in the bucket, so point this
> + * inode to the current head of the list.
> + */
> + error = iunlink_log_dinode(tp, ip, pag, next_agino);
> + if (error)
> + return error;
> + }
> +
> + /* Update the bucket. */
> + agi->agi_unlinked[bucket_index] = cpu_to_be32(agino);
> + offset = offsetof(struct xfs_agi, agi_unlinked) +
> + (sizeof(xfs_agino_t) * bucket_index);
> + libxfs_trans_log_buf(tp, agibp, offset,
> + offset + sizeof(xfs_agino_t) - 1);
> + return 0;
> +}
> +
> +/*
> + * This is called when the inode's link count has gone to 0 or we are creating
> + * a tmpfile via O_TMPFILE. The inode @ip must have nlink == 0.
> + *
> + * We place the on-disk inode on a list in the AGI. It will be pulled from this
> + * list when the inode is freed.
> + */
> +static int
> +iunlink(
> + struct xfs_trans *tp,
> + struct xfs_inode *ip)
> +{
> + struct xfs_mount *mp = tp->t_mountp;
> + struct xfs_perag *pag;
> + struct xfs_buf *agibp;
> + int error;
> +
> + ASSERT(VFS_I(ip)->i_nlink == 0);
> + ASSERT(VFS_I(ip)->i_mode != 0);
> +
> + pag = libxfs_perag_get(mp, XFS_INO_TO_AGNO(mp, ip->i_ino));
> +
> + /* Get the agi buffer first. It ensures lock ordering on the list. */
> + error = -libxfs_read_agi(pag, tp, &agibp);
> + if (error)
> + goto out;
> +
> + error = iunlink_insert_inode(tp, pag, agibp, ip);
> +out:
> + libxfs_perag_put(pag);
> + return error;
> +}
> +
> +static int
> +create_unlinked(
> + struct xfs_mount *mp)
> +{
> + struct cred cr = { };
> + struct fsxattr fsx = { };
> + struct xfs_inode *ip;
> + struct xfs_trans *tp;
> + unsigned int resblks;
> + int error;
> +
> + resblks = XFS_IALLOC_SPACE_RES(mp);
> + error = -libxfs_trans_alloc(mp, &M_RES(mp)->tr_create_tmpfile, resblks,
> + 0, 0, &tp);
> + if (error) {
> + dbprintf(_("alloc trans: %s\n"), strerror(error));
> + return error;
> + }
> +
> + error = -libxfs_dir_ialloc(&tp, NULL, S_IFREG | 0600, 0, 0, &cr, &fsx,
> + &ip);
> + if (error) {
> + dbprintf(_("create inode: %s\n"), strerror(error));
> + goto out_cancel;
> + }
> +
> + error = iunlink(tp, ip);
> + if (error) {
> + dbprintf(_("unlink inode: %s\n"), strerror(error));
> + goto out_rele;
> + }
> +
> + error = -libxfs_trans_commit(tp);
> + if (error)
> + dbprintf(_("commit inode: %s\n"), strerror(error));
> +
> + dbprintf(_("Created unlinked inode %llu in agno %u\n"),
> + (unsigned long long)ip->i_ino,
> + XFS_INO_TO_AGNO(mp, ip->i_ino));
> + libxfs_irele(ip);
> + return error;
> +out_rele:
> + libxfs_irele(ip);
> +out_cancel:
> + libxfs_trans_cancel(tp);
> + return error;
> +}
> +
> +static int
> +iunlink_f(
> + int argc,
> + char **argv)
> +{
> + int nr = 1;
> + int c;
> + int error;
> +
> + while ((c = getopt(argc, argv, "n:")) != EOF) {
> + switch (c) {
> + case 'n':
> + nr = atoi(optarg);
> + if (nr <= 0) {
> + dbprintf(_("%s: need positive number\n"));
> + return 0;
> + }
> + break;
> + default:
> + dbprintf(_("Bad option for iunlink command.\n"));
> + return 0;
> + }
> + }
> +
> + for (c = 0; c < nr; c++) {
> + error = create_unlinked(mp);
> + if (error)
> + return 1;
> + }
> +
> + return 0;
> +}
> +
> +static const cmdinfo_t iunlink_cmd =
> + { "iunlink", NULL, iunlink_f, 0, -1, 0,
> + N_("[-n nr]"),
> + N_("allocate inodes and put them on the unlinked list"), NULL };
> +
> void
> iunlink_init(void)
> {
> add_command(&dump_iunlinked_cmd);
> + if (expert_mode)
> + add_command(&iunlink_cmd);
> }
> diff --git a/libxfs/libxfs_api_defs.h b/libxfs/libxfs_api_defs.h
> index ddba5c7c..04277c00 100644
> --- a/libxfs/libxfs_api_defs.h
> +++ b/libxfs/libxfs_api_defs.h
> @@ -149,6 +149,7 @@
> #define xfs_prealloc_blocks libxfs_prealloc_blocks
>
> #define xfs_read_agf libxfs_read_agf
> +#define xfs_read_agi libxfs_read_agi
> #define xfs_refc_block libxfs_refc_block
> #define xfs_refcountbt_calc_reserves libxfs_refcountbt_calc_reserves
> #define xfs_refcountbt_calc_size libxfs_refcountbt_calc_size
> diff --git a/man/man8/xfs_db.8 b/man/man8/xfs_db.8
> index 2d6d0da4..f53ddd67 100644
> --- a/man/man8/xfs_db.8
> +++ b/man/man8/xfs_db.8
> @@ -840,6 +840,17 @@ Set the current inode number. If no
> .I inode#
> is given, print the current inode number.
> .TP
> +.BI "iunlink [-n " nr " ]"
> +Allocate inodes and put them on the unlinked list.
> +
> +Options include:
> +.RS 1.0i
> +.TP 0.4i
> +.B \-n
> +Create this number of unlinked inodes.
> +If not specified, 1 inode will be created.
> +.RE
> +.TP
> .BI "label [" label ]
> Set the filesystem label. The filesystem label can be used by
> .BR mount (8)
>
