[PATCH 1/5] repair: handle repair of image files on large sector size filesystems

Dave Chinner
2011-10-10T01:08:42Z

From: Dave Chinner <dchinner@redhat.com>

Because repair uses direct IO, it cannot do IO smaller than a sector
on the underlying device. When repairing a filesystem image, the
filesystem hosting the image may have a sector size larger than the
sector size of the image, and so single image sector reads and
writes will fail.

To avoid this, when checking a file and there is a sector size
mismatch like this, turn off direct IO. While there, fix a compile
bug in the IO_DEBUG option for libxfs which was found during triage.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
---
libxfs/rdwr.c | 2 +-
repair/sb.c | 9 ++++++++-
repair/xfs_repair.c | 29 +++++++++++++++++++++++++++++
3 files changed, 38 insertions(+), 2 deletions(-)

diff --git a/libxfs/rdwr.c b/libxfs/rdwr.c
index fe8ae09..c3edb89 100644
--- a/libxfs/rdwr.c
+++ b/libxfs/rdwr.c
@@ -365,7 +365,7 @@ libxfs_getbufr(dev_t device, xfs_daddr_t blkno, int bblen)
libxfs_initbuf(bp, device, blkno, blen);
#ifdef IO_DEBUG
printf("%lx: %s: allocated %u bytes buffer, key=%llu(%llu), %p\n",
- pthread_self(), __FUNCTION__, BBTOB(len),
+ pthread_self(), __FUNCTION__, blen,
(long long)LIBXFS_BBTOOFF64(blkno), (long long)blkno, bp);
#endif

diff --git a/repair/sb.c b/repair/sb.c
index 6d2e91a..004319f 100644
--- a/repair/sb.c
+++ b/repair/sb.c
@@ -689,7 +689,14 @@ verify_set_primary_sb(xfs_sb_t *rsb,
*/
num_sbs = MIN(NUM_SBS, rsb->sb_agcount);
skip = howmany(num_sbs, rsb->sb_agcount);
- size = NUM_AGH_SECTS * rsb->sb_sectsize;
+
+ /*
+ * We haven't been able to validate the sector size yet properly
+ * (e.g. in the case of repairing an image in a file), so we need to
+ * take into account sector mismatches and so use the maximum possible
+ * sector size rather than the sector size in @rsb.
+ */
+ size = NUM_AGH_SECTS * (1 << (XFS_MAX_SECTORSIZE_LOG));
retval = 0;
list = NULL;
num_ok = 0;
diff --git a/repair/xfs_repair.c b/repair/xfs_repair.c
index 4e2b022..69b7eab 100644
--- a/repair/xfs_repair.c
+++ b/repair/xfs_repair.c
@@ -569,6 +569,35 @@ main(int argc, char **argv)
memset(&xfs_m, 0, sizeof(xfs_mount_t));
libxfs_sb_from_disk(&xfs_m.m_sb, XFS_BUF_TO_SBP(sbp));

+ /*
+ * if the sector size of the filesystem we are trying to repair is
+ * smaller than that of the underlying filesystem (i.e. we are repairing
+ * an image), the we have to turn off direct IO because we cannot do IO
+ * smaller than the host filesystem's sector size.
+ */
+ if (isa_file) {
+ int fd = libxfs_device_to_fd(x.ddev);
+ struct xfs_fsop_geom_v1 geom = { 0 };
+
+ if (ioctl(fd, XFS_IOC_FSGEOMETRY_V1, &geom) < 0) {
+ do_warn(_("Cannot get host filesystem geometry.\n"
+ "Repair may fail if there is a sector size mismatch between\n"
+ "the image and the host filesystem.\n"));
+ geom.sectsize = BBSIZE;
+ }
+
+ if (xfs_m.m_sb.sb_sectsize < geom.sectsize) {
+ long old_flags;
+
+ old_flags = fcntl(fd, F_GETFL, 0);
+ if (fcntl(fd, F_SETFL, old_flags & ~O_DIRECT) < 0) {
+ do_warn(_(
+ "Sector size on host filesystem larger than image sector size.\n"
+ "Cannot turn off direct IO, so exiting.\n"));
+ exit(1);
+ }
+ }
+ }
mp = libxfs_mount(&xfs_m, &xfs_m.m_sb, x.ddev, x.logdev, x.rtdev, 0);

if (!mp) {
--
1.7.5.4