[PATCH 1/6] xfs: check rt bitmap file geometry more thoroughly

Darrick J. Wong
2023-11-24T23:54:28Z

From: Darrick J. Wong <djwong@kernel.org>

I forgot that the superblock tracks the number of blocks that are in the
realtime bitmap, and that the rt bitmap file can have more blocks mapped
to the data fork than sb_rbmblocks if growfsrt fails.

So. Add to the rtbitmap scrubber an explicit check that sb_rextents and
sb_rbmblocks are correct, then adjust the rtbitmap i_size checks to
allow for the growfsrt failure case. Finally, flag post-eof blocks in
the rtbitmap.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
---
fs/xfs/scrub/rtbitmap.c | 97 ++++++++++++++++++++++++++++++++++++++++-------
1 file changed, 82 insertions(+), 15 deletions(-)

diff --git a/fs/xfs/scrub/rtbitmap.c b/fs/xfs/scrub/rtbitmap.c
index d509a08d3fc3e..3b5b62fbf4e0a 100644
--- a/fs/xfs/scrub/rtbitmap.c
+++ b/fs/xfs/scrub/rtbitmap.c
@@ -14,16 +14,30 @@
#include "xfs_rtbitmap.h"
#include "xfs_inode.h"
#include "xfs_bmap.h"
+#include "xfs_bit.h"
#include "scrub/scrub.h"
#include "scrub/common.h"

+struct xchk_rtbitmap {
+ uint64_t rextents;
+ uint64_t rbmblocks;
+ unsigned int rextslog;
+};
+
/* Set us up with the realtime metadata locked. */
int
xchk_setup_rtbitmap(
struct xfs_scrub *sc)
{
+ struct xfs_mount *mp = sc->mp;
+ struct xchk_rtbitmap *rtb;
int error;

+ rtb = kzalloc(sizeof(struct xchk_rtbitmap), XCHK_GFP_FLAGS);
+ if (!rtb)
+ return -ENOMEM;
+ sc->buf = rtb;
+
error = xchk_trans_alloc(sc, 0);
if (error)
return error;
@@ -37,6 +51,15 @@ xchk_setup_rtbitmap(
return error;

xchk_ilock(sc, XFS_ILOCK_EXCL | XFS_ILOCK_RTBITMAP);
+
+ /*
+ * Now that we've locked the rtbitmap, we can't race with growfsrt
+ * trying to expand the bitmap or change the size of the rt volume.
+ * Hence it is safe to compute and check the geometry values.
+ */
+ rtb->rextents = xfs_rtb_to_rtx(mp, mp->m_sb.sb_rblocks);
+ rtb->rextslog = rtb->rextents ? xfs_highbit32(rtb->rextents) : 0;
+ rtb->rbmblocks = xfs_rtbitmap_blockcount(mp, rtb->rextents);
return 0;
}

@@ -67,21 +90,30 @@ STATIC int
xchk_rtbitmap_check_extents(
struct xfs_scrub *sc)
{
- struct xfs_mount *mp = sc->mp;
struct xfs_bmbt_irec map;
- xfs_rtblock_t off;
- int nmap;
+ struct xfs_iext_cursor icur;
+ struct xfs_mount *mp = sc->mp;
+ struct xfs_inode *ip = sc->ip;
+ xfs_fileoff_t off = 0;
+ xfs_fileoff_t endoff;
int error = 0;

- for (off = 0; off < mp->m_sb.sb_rbmblocks;) {
+ /* Mappings may not cross or lie beyond EOF. */
+ endoff = XFS_B_TO_FSB(mp, ip->i_disk_size);
+ if (xfs_iext_lookup_extent(ip, &ip->i_df, endoff, &icur, &map)) {
+ xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, endoff);
+ return 0;
+ }
+
+ while (off < endoff) {
+ int nmap = 1;
+
if (xchk_should_terminate(sc, &error) ||
(sc->sm->sm_flags & XFS_SCRUB_OFLAG_CORRUPT))
break;

/* Make sure we have a written extent. */
- nmap = 1;
- error = xfs_bmapi_read(mp->m_rbmip, off,
- mp->m_sb.sb_rbmblocks - off, &map, &nmap,
+ error = xfs_bmapi_read(ip, off, endoff - off, &map, &nmap,
XFS_DATA_FORK);
if (!xchk_fblock_process_error(sc, XFS_DATA_FORK, off, &error))
break;
@@ -102,12 +134,48 @@ int
xchk_rtbitmap(
struct xfs_scrub *sc)
{
+ struct xfs_mount *mp = sc->mp;
+ struct xchk_rtbitmap *rtb = sc->buf;
int error;

- /* Is the size of the rtbitmap correct? */
- if (sc->mp->m_rbmip->i_disk_size !=
- XFS_FSB_TO_B(sc->mp, sc->mp->m_sb.sb_rbmblocks)) {
- xchk_ino_set_corrupt(sc, sc->mp->m_rbmip->i_ino);
+ /* Is sb_rextents correct? */
+ if (mp->m_sb.sb_rextents != rtb->rextents) {
+ xchk_ino_set_corrupt(sc, mp->m_rbmip->i_ino);
+ return 0;
+ }
+
+ /* Is sb_rextslog correct? */
+ if (mp->m_sb.sb_rextslog != rtb->rextslog) {
+ xchk_ino_set_corrupt(sc, mp->m_rbmip->i_ino);
+ return 0;
+ }
+
+ /*
+ * Is sb_rbmblocks large enough to handle the current rt volume? In no
+ * case can we exceed 4bn bitmap blocks since the super field is a u32.
+ */
+ if (rtb->rbmblocks > U32_MAX) {
+ xchk_ino_set_corrupt(sc, mp->m_rbmip->i_ino);
+ return 0;
+ }
+ if (mp->m_sb.sb_rbmblocks != rtb->rbmblocks) {
+ xchk_ino_set_corrupt(sc, mp->m_rbmip->i_ino);
+ return 0;
+ }
+
+ /* The bitmap file length must be aligned to an fsblock. */
+ if (mp->m_rbmip->i_disk_size & mp->m_blockmask) {
+ xchk_ino_set_corrupt(sc, mp->m_rbmip->i_ino);
+ return 0;
+ }
+
+ /*
+ * Is the bitmap file itself large enough to handle the rt volume?
+ * growfsrt expands the bitmap file before updating sb_rextents, so the
+ * file can be larger than sb_rbmblocks.
+ */
+ if (mp->m_rbmip->i_disk_size < XFS_FSB_TO_B(mp, rtb->rbmblocks)) {
+ xchk_ino_set_corrupt(sc, mp->m_rbmip->i_ino);
return 0;
}

@@ -120,12 +188,11 @@ xchk_rtbitmap(
if (error || (sc->sm->sm_flags & XFS_SCRUB_OFLAG_CORRUPT))
return error;

- error = xfs_rtalloc_query_all(sc->mp, sc->tp, xchk_rtbitmap_rec, sc);
+ error = xfs_rtalloc_query_all(mp, sc->tp, xchk_rtbitmap_rec, sc);
if (!xchk_fblock_process_error(sc, XFS_DATA_FORK, 0, &error))
- goto out;
+ return error;

-out:
- return error;
+ return 0;
}

/* xref check that the extent is not free in the rtbitmap */