[PATCH v3] repair: handle reading superblock from image on larger sector size filesystem

Zorro Lang
2017-04-06T12:05:29Z

Due to xfs_repair uses direct IO, sometimes it can't read superblock
from an image file has smaller sector size than host filesystem.
Especially that superblock doesn't align with host filesystem's
sector size.

Fortunately, xfsprogs already has code to do isa_file and geometry
check in xfs_repair.c, it turns off O_DIRECT after phase1() if the
sector size is less than the host filesystem's geometry. So move
the isa_file auto detection over up the phase1(), and try to do
once geometry check before phase1() if get_sb() return OK.

Signed-off-by: Zorro Lang <zlang@redhat.com>
---

Hi,

V2 did a stupid change, it tried to check superblock before get_sb(). So
V3 fix this problem by below changes:

1) move the "if (!isa_file)" auto detection over up the phase1().
2) try to get_sb() before phase1, and check the sector size. Turn
off the O_DIRECT if the sector size is smaller than the underlying
filesystem.
3) The step#2 maybe fail, due to can't get a valid primary superblock.
So keep the similar steps after phase1(), I didn't remove it.

Thanks,
Zorro

repair/xfs_repair.c | 96 ++++++++++++++++++++++++++++++-----------------------
1 file changed, 54 insertions(+), 42 deletions(-)

diff --git a/repair/xfs_repair.c b/repair/xfs_repair.c
index b07567b..9df5719 100644
--- a/repair/xfs_repair.c
+++ b/repair/xfs_repair.c
@@ -627,6 +627,42 @@ is_multidisk_filesystem(
return true;
}

+/*
+ * 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.
+ */
+static void
+check_geometry_sectsize(
+ struct xfs_sb *sb)
+{
+ int fd;
+ long old_flags;
+ struct xfs_fsop_geom_v1 geom = { 0 };
+
+ if (isa_file) {
+ fd = libxfs_device_to_fd(x.ddev);
+
+ if (ioctl(fd, XFS_IOC_FSGEOMETRY_V1, &geom) < 0) {
+ do_log(_("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 (sb->sb_sectsize < geom.sectsize) {
+ 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);
+ }
+ }
+ }
+}
+
int
main(int argc, char **argv)
{
@@ -657,6 +693,23 @@ main(int argc, char **argv)
timestamp(PHASE_START, 0, NULL);
timestamp(PHASE_END, 0, NULL);

+ /* -f forces this, but let's be nice and autodetect it, as well. */
+ if (!isa_file) {
+ int fd = libxfs_device_to_fd(x.ddev);
+ struct stat statbuf;
+
+ if (fstat(fd, &statbuf) < 0)
+ do_warn(_("%s: couldn't stat \"%s\"\n"),
+ progname, fs_name);
+ else if (S_ISREG(statbuf.st_mode))
+ isa_file = 1;
+ }
+
+ rval = get_sb(&psb, 0, XFS_MAX_SECTORSIZE, 0);
+ if (rval == XR_OK) {
+ check_geometry_sectsize(&psb);
+ }
+
/* do phase1 to make sure we have a superblock */
phase1(temp_mp);
timestamp(PHASE_END, 1, NULL);
@@ -674,48 +727,7 @@ main(int argc, char **argv)
"Exiting now.\n"));
exit(1);
}
-
- /* -f forces this, but let's be nice and autodetect it, as well. */
- if (!isa_file) {
- int fd = libxfs_device_to_fd(x.ddev);
- struct stat statbuf;
-
- if (fstat(fd, &statbuf) < 0)
- do_warn(_("%s: couldn't stat \"%s\"\n"),
- progname, fs_name);
- else if (S_ISREG(statbuf.st_mode))
- isa_file = 1;
- }
-
- /*
- * 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_log(_("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 (psb.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);
- }
- }
- }
+ check_geometry_sectsize(&psb);

/*
* Prepare the mount structure. Point the log reference to our local
--
2.7.4