Illumos 6451 - ztest fails due to checksum errors

6451 ztest fails due to checksum errors
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Prakash Surya <prakash.surya@delphix.com>
Reviewed by: Jorgen Lundman <lundman@lundman.net>
Approved by: Dan McDonald <danmcd@omniti.com>

References:
  https://www.illumos.org/issues/6451
  https://github.com/illumos/illumos-gate/commit/f9eb9fd

Ported-by: Brian Behlendorf <behlendorf1@llnl.gov>

diff --git a/cmd/ztest/ztest.c b/cmd/ztest/ztest.c
index 026fe541709a808a1555eb319569956bcc46939d..42643ef5d06350811874fecc5e0741fc69882309 100644 (file)
--- a/cmd/ztest/ztest.c
+++ b/cmd/ztest/ztest.c
@@ -4972,7 +4972,7 @@ ztest_fault_inject(ztest_ds_t *zd, uint64_t id)
        char *path0;
        char *pathrand;
        size_t fsize;
-       int bshift = SPA_OLD_MAXBLOCKSHIFT + 2; /* don't scrog all labels */
+       int bshift = SPA_MAXBLOCKSHIFT + 2;     /* don't scrog all labels */
        int iters = 1000;
        int maxfaults;
        int mirror_save;
@@ -5136,6 +5136,31 @@ ztest_fault_inject(ztest_ds_t *zd, uint64_t id)
        fsize = lseek(fd, 0, SEEK_END);
 
        while (--iters != 0) {
+               /*
+                * The offset must be chosen carefully to ensure that
+                * we do not inject a given logical block with errors
+                * on two different leaf devices, because ZFS can not
+                * tolerate that (if maxfaults==1).
+                *
+                * We divide each leaf into chunks of size
+                * (# leaves * SPA_MAXBLOCKSIZE * 4).  Within each chunk
+                * there is a series of ranges to which we can inject errors.
+                * Each range can accept errors on only a single leaf vdev.
+                * The error injection ranges are separated by ranges
+                * which we will not inject errors on any device (DMZs).
+                * Each DMZ must be large enough such that a single block
+                * can not straddle it, so that a single block can not be
+                * a target in two different injection ranges (on different
+                * leaf vdevs).
+                *
+                * For example, with 3 leaves, each chunk looks like:
+                *    0 to  32M: injection range for leaf 0
+                *  32M to  64M: DMZ - no injection allowed
+                *  64M to  96M: injection range for leaf 1
+                *  96M to 128M: DMZ - no injection allowed
+                * 128M to 160M: injection range for leaf 2
+                * 160M to 192M: DMZ - no injection allowed
+                */
                offset = ztest_random(fsize / (leaves << bshift)) *
                    (leaves << bshift) + (leaf << bshift) +
                    (ztest_random(1ULL << (bshift - 1)) & -8ULL);