[PATCH 2/3] libxfs: simulate system failure after a certain number of writes

Darrick J. Wong
2021-02-13T05:47:42Z

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

Add an error injection knob so that we can simulate system failure after
a certain number of disk writes. This knob is being added so that we
can check repair's behavior after an arbitrary number of tests.

Set LIBXFS_DEBUG_WRITE_CRASH={ddev,logdev,rtdev}=nn in the environment
to make libxfs SIGKILL itself after nn writes to the data, log, or rt
devices. Note that this only applies to xfs_buf writes and zero_range.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
---
libxfs/init.c | 68 +++++++++++++++++++++++++++++++++++++++++++++++++---
libxfs/libxfs_io.h | 19 +++++++++++++++
libxfs/rdwr.c | 6 ++++-
3 files changed, 88 insertions(+), 5 deletions(-)

diff --git a/libxfs/init.c b/libxfs/init.c
index 8a8ce3c4..1ec83791 100644
--- a/libxfs/init.c
+++ b/libxfs/init.c
@@ -590,7 +590,8 @@ libxfs_initialize_perag(
static struct xfs_buftarg *
libxfs_buftarg_alloc(
struct xfs_mount *mp,
- dev_t dev)
+ dev_t dev,
+ unsigned long write_fails)
{
struct xfs_buftarg *btp;

@@ -603,10 +604,29 @@ libxfs_buftarg_alloc(
btp->bt_mount = mp;
btp->bt_bdev = dev;
btp->flags = 0;
+ if (write_fails) {
+ btp->writes_left = write_fails;
+ btp->flags |= XFS_BUFTARG_INJECT_WRITE_FAIL;
+ }
+ pthread_mutex_init(&btp->lock, NULL);

return btp;
}

+enum libxfs_write_failure_nums {
+ WF_DATA = 0,
+ WF_LOG,
+ WF_RT,
+ WF_MAX_OPTS,
+};
+
+static char *wf_opts[] = {
+ [WF_DATA] = "ddev",
+ [WF_LOG] = "logdev",
+ [WF_RT] = "rtdev",
+ [WF_MAX_OPTS] = NULL,
+};
+
void
libxfs_buftarg_init(
struct xfs_mount *mp,
@@ -614,6 +634,46 @@ libxfs_buftarg_init(
dev_t logdev,
dev_t rtdev)
{
+ char *p = getenv("LIBXFS_DEBUG_WRITE_CRASH");
+ unsigned long dfail = 0, lfail = 0, rfail = 0;
+
+ /* Simulate utility crash after a certain number of writes. */
+ while (p && *p) {
+ char *val;
+
+ switch (getsubopt(&p, wf_opts, &val)) {
+ case WF_DATA:
+ if (!val) {
+ fprintf(stderr,
+ _("ddev write fail requires a parameter\n"));
+ exit(1);
+ }
+ dfail = strtoul(val, NULL, 0);
+ break;
+ case WF_LOG:
+ if (!val) {
+ fprintf(stderr,
+ _("logdev write fail requires a parameter\n"));
+ exit(1);
+ }
+ lfail = strtoul(val, NULL, 0);
+ break;
+ case WF_RT:
+ if (!val) {
+ fprintf(stderr,
+ _("rtdev write fail requires a parameter\n"));
+ exit(1);
+ }
+ rfail = strtoul(val, NULL, 0);
+ break;
+ default:
+ fprintf(stderr, _("unknown write fail type %s\n"),
+ val);
+ exit(1);
+ break;
+ }
+ }
+
if (mp->m_ddev_targp) {
/* should already have all buftargs initialised */
if (mp->m_ddev_targp->bt_bdev != dev ||
@@ -647,12 +707,12 @@ libxfs_buftarg_init(
return;
}

- mp->m_ddev_targp = libxfs_buftarg_alloc(mp, dev);
+ mp->m_ddev_targp = libxfs_buftarg_alloc(mp, dev, dfail);
if (!logdev || logdev == dev)
mp->m_logdev_targp = mp->m_ddev_targp;
else
- mp->m_logdev_targp = libxfs_buftarg_alloc(mp, logdev);
- mp->m_rtdev_targp = libxfs_buftarg_alloc(mp, rtdev);
+ mp->m_logdev_targp = libxfs_buftarg_alloc(mp, logdev, lfail);
+ mp->m_rtdev_targp = libxfs_buftarg_alloc(mp, rtdev, rfail);
}

/*
diff --git a/libxfs/libxfs_io.h b/libxfs/libxfs_io.h
index c80e2d59..85485257 100644
--- a/libxfs/libxfs_io.h
+++ b/libxfs/libxfs_io.h
@@ -22,6 +22,8 @@ struct xfs_perag;
*/
struct xfs_buftarg {
struct xfs_mount *bt_mount;
+ pthread_mutex_t lock;
+ unsigned long writes_left;
dev_t bt_bdev;
unsigned int flags;
};
@@ -30,6 +32,23 @@ struct xfs_buftarg {
#define XFS_BUFTARG_LOST_WRITE (1 << 0)
/* A dirty buffer failed the write verifier. */
#define XFS_BUFTARG_CORRUPT_WRITE (1 << 1)
+/* Simulate failure after a certain number of writes. */
+#define XFS_BUFTARG_INJECT_WRITE_FAIL (1 << 2)
+
+/* Simulate the system crashing after a write. */
+static inline void
+xfs_buftarg_trip_write(
+ struct xfs_buftarg *btp)
+{
+ if (!(btp->flags & XFS_BUFTARG_INJECT_WRITE_FAIL))
+ return;
+
+ pthread_mutex_lock(&btp->lock);
+ btp->writes_left--;
+ if (!btp->writes_left)
+ kill(getpid(), SIGKILL);
+ pthread_mutex_unlock(&btp->lock);
+}

extern void libxfs_buftarg_init(struct xfs_mount *mp, dev_t ddev,
dev_t logdev, dev_t rtdev);
diff --git a/libxfs/rdwr.c b/libxfs/rdwr.c
index ca272387..fd456d6b 100644
--- a/libxfs/rdwr.c
+++ b/libxfs/rdwr.c
@@ -74,8 +74,10 @@ libxfs_device_zero(struct xfs_buftarg *btp, xfs_daddr_t start, uint len)
/* try to use special zeroing methods, fall back to writes if needed */
len_bytes = LIBXFS_BBTOOFF64(len);
error = platform_zero_range(fd, start_offset, len_bytes);
- if (!error)
+ if (!error) {
+ xfs_buftarg_trip_write(btp);
return 0;
+ }

zsize = min(BDSTRAT_SIZE, BBTOB(len));
if ((z = memalign(libxfs_device_alignment(), zsize)) == NULL) {
@@ -105,6 +107,7 @@ libxfs_device_zero(struct xfs_buftarg *btp, xfs_daddr_t start, uint len)
progname, __FUNCTION__);
exit(1);
}
+ xfs_buftarg_trip_write(btp);
offset += bytes;
}
free(z);
@@ -860,6 +863,7 @@ libxfs_bwrite(
} else {
bp->b_flags |= LIBXFS_B_UPTODATE;
bp->b_flags &= ~(LIBXFS_B_DIRTY | LIBXFS_B_UNCHECKED);
+ xfs_buftarg_trip_write(bp->b_target);
}
return bp->b_error;
}