svn commit: r322226 - in head: cddl/contrib/opensolaris/cmd/ztest sys/cddl/contrib/opensolaris/uts/common/fs/zfs
Andriy Gapon
avg at FreeBSD.org
Tue Aug 8 10:46:53 UTC 2017
Author: avg
Date: Tue Aug 8 10:46:51 2017
New Revision: 322226
URL: https://svnweb.freebsd.org/changeset/base/322226
Log:
MFV r322223: 8378 crash due to bp in-memory modification of nopwrite block
illumos/illumos-gate at b7edcb940884114e61382937505433c4c38c0278
https://github.com/illumos/illumos-gate/commit/b7edcb940884114e61382937505433c4c38c0278
https://www.illumos.org/issues/8378
The problem is that zfs_get_data() supplies a stale zgd_bp to dmu_sync(), which
we then nopwrite against.
zfs_get_data() doesn't hold any DMU-related locks, so after it copies db_blkptr
to zgd_bp, dbuf_write_ready()
could change db_blkptr, and dbuf_write_done() could remove the dirty record.
dmu_sync() then sees the stale
BP and that the dbuf it not dirty, so it is eligible for nop-writing.
The fix is for dmu_sync() to copy db_blkptr to zgd_bp after acquiring the
db_mtx. We could still see a stale
db_blkptr, but if it is stale then the dirty record will still exist and thus
we won't attempt to nopwrite.
Reviewed by: Prakash Surya <prakash.surya at delphix.com>
Reviewed by: George Wilson <george.wilson at delphix.com>
Approved by: Robert Mustacchi <rm at joyent.com>
Author: Matthew Ahrens <mahrens at delphix.com>
MFC after: 2 weeks
Modified:
head/cddl/contrib/opensolaris/cmd/ztest/ztest.c
head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu.c
head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vnops.c
head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zvol.c
Directory Properties:
head/cddl/contrib/opensolaris/ (props changed)
head/sys/cddl/contrib/opensolaris/ (props changed)
Modified: head/cddl/contrib/opensolaris/cmd/ztest/ztest.c
==============================================================================
--- head/cddl/contrib/opensolaris/cmd/ztest/ztest.c Tue Aug 8 10:45:22 2017 (r322225)
+++ head/cddl/contrib/opensolaris/cmd/ztest/ztest.c Tue Aug 8 10:46:51 2017 (r322226)
@@ -1838,7 +1838,6 @@ ztest_get_data(void *arg, lr_write_t *lr, char *buf, z
uint64_t object = lr->lr_foid;
uint64_t offset = lr->lr_offset;
uint64_t size = lr->lr_length;
- blkptr_t *bp = &lr->lr_blkptr;
uint64_t txg = lr->lr_common.lrc_txg;
uint64_t crtxg;
dmu_object_info_t doi;
@@ -1892,11 +1891,7 @@ ztest_get_data(void *arg, lr_write_t *lr, char *buf, z
DMU_READ_NO_PREFETCH);
if (error == 0) {
- blkptr_t *obp = dmu_buf_get_blkptr(db);
- if (obp) {
- ASSERT(BP_IS_HOLE(bp));
- *bp = *obp;
- }
+ blkptr_t *bp = &lr->lr_blkptr;
zgd->zgd_db = db;
zgd->zgd_bp = bp;
Modified: head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu.c
==============================================================================
--- head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu.c Tue Aug 8 10:45:22 2017 (r322225)
+++ head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu.c Tue Aug 8 10:46:51 2017 (r322226)
@@ -1657,6 +1657,7 @@ dmu_sync_done(zio_t *zio, arc_buf_t *buf, void *varg)
uint8_t chksum = BP_GET_CHECKSUM(bp_orig);
ASSERT(BP_EQUAL(bp, bp_orig));
+ VERIFY(BP_EQUAL(bp, db->db_blkptr));
ASSERT(zio->io_prop.zp_compress != ZIO_COMPRESS_OFF);
ASSERT(zio_checksum_table[chksum].ci_flags &
ZCHECKSUM_FLAG_NOPWRITE);
@@ -1697,19 +1698,11 @@ dmu_sync_late_arrival_done(zio_t *zio)
blkptr_t *bp_orig = &zio->io_bp_orig;
if (zio->io_error == 0 && !BP_IS_HOLE(bp)) {
- /*
- * If we didn't allocate a new block (i.e. ZIO_FLAG_NOPWRITE)
- * then there is nothing to do here. Otherwise, free the
- * newly allocated block in this txg.
- */
- if (zio->io_flags & ZIO_FLAG_NOPWRITE) {
- ASSERT(BP_EQUAL(bp, bp_orig));
- } else {
- ASSERT(BP_IS_HOLE(bp_orig) || !BP_EQUAL(bp, bp_orig));
- ASSERT(zio->io_bp->blk_birth == zio->io_txg);
- ASSERT(zio->io_txg > spa_syncing_txg(zio->io_spa));
- zio_free(zio->io_spa, zio->io_txg, zio->io_bp);
- }
+ ASSERT(!(zio->io_flags & ZIO_FLAG_NOPWRITE));
+ ASSERT(BP_IS_HOLE(bp_orig) || !BP_EQUAL(bp, bp_orig));
+ ASSERT(zio->io_bp->blk_birth == zio->io_txg);
+ ASSERT(zio->io_txg > spa_syncing_txg(zio->io_spa));
+ zio_free(zio->io_spa, zio->io_txg, zio->io_bp);
}
dmu_tx_commit(dsa->dsa_tx);
@@ -1741,6 +1734,29 @@ dmu_sync_late_arrival(zio_t *pio, objset_t *os, dmu_sy
dsa->dsa_zgd = zgd;
dsa->dsa_tx = tx;
+ /*
+ * Since we are currently syncing this txg, it's nontrivial to
+ * determine what BP to nopwrite against, so we disable nopwrite.
+ *
+ * When syncing, the db_blkptr is initially the BP of the previous
+ * txg. We can not nopwrite against it because it will be changed
+ * (this is similar to the non-late-arrival case where the dbuf is
+ * dirty in a future txg).
+ *
+ * Then dbuf_write_ready() sets bp_blkptr to the location we will write.
+ * We can not nopwrite against it because although the BP will not
+ * (typically) be changed, the data has not yet been persisted to this
+ * location.
+ *
+ * Finally, when dbuf_write_done() is called, it is theoretically
+ * possible to always nopwrite, because the data that was written in
+ * this txg is the same data that we are trying to write. However we
+ * would need to check that this dbuf is not dirty in any future
+ * txg's (as we do in the normal dmu_sync() path). For simplicity, we
+ * don't nopwrite in this case.
+ */
+ zp->zp_nopwrite = B_FALSE;
+
zio_nowait(zio_write(pio, os->os_spa, dmu_tx_get_txg(tx), zgd->zgd_bp,
abd_get_from_buf(zgd->zgd_db->db_data, zgd->zgd_db->db_size),
zgd->zgd_db->db_size, zgd->zgd_db->db_size, zp,
@@ -1778,7 +1794,6 @@ dmu_sync_late_arrival(zio_t *pio, objset_t *os, dmu_sy
int
dmu_sync(zio_t *pio, uint64_t txg, dmu_sync_cb_t *done, zgd_t *zgd)
{
- blkptr_t *bp = zgd->zgd_bp;
dmu_buf_impl_t *db = (dmu_buf_impl_t *)zgd->zgd_db;
objset_t *os = db->db_objset;
dsl_dataset_t *ds = os->os_dsl_dataset;
@@ -1845,6 +1860,21 @@ dmu_sync(zio_t *pio, uint64_t txg, dmu_sync_cb_t *done
ASSERT(dr->dr_next == NULL || dr->dr_next->dr_txg < txg);
+ if (db->db_blkptr != NULL) {
+ /*
+ * We need to fill in zgd_bp with the current blkptr so that
+ * the nopwrite code can check if we're writing the same
+ * data that's already on disk. We can only nopwrite if we
+ * are sure that after making the copy, db_blkptr will not
+ * change until our i/o completes. We ensure this by
+ * holding the db_mtx, and only allowing nopwrite if the
+ * block is not already dirty (see below). This is verified
+ * by dmu_sync_done(), which VERIFYs that the db_blkptr has
+ * not changed.
+ */
+ *zgd->zgd_bp = *db->db_blkptr;
+ }
+
/*
* Assume the on-disk data is X, the current syncing data (in
* txg - 1) is Y, and the current in-memory data is Z (currently
@@ -1896,7 +1926,7 @@ dmu_sync(zio_t *pio, uint64_t txg, dmu_sync_cb_t *done
dsa->dsa_tx = NULL;
zio_nowait(arc_write(pio, os->os_spa, txg,
- bp, dr->dt.dl.dr_data, DBUF_IS_L2CACHEABLE(db),
+ zgd->zgd_bp, dr->dt.dl.dr_data, DBUF_IS_L2CACHEABLE(db),
&zp, dmu_sync_ready, NULL, NULL, dmu_sync_done, dsa,
ZIO_PRIORITY_SYNC_WRITE, ZIO_FLAG_CANFAIL, &zb));
Modified: head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vnops.c
==============================================================================
--- head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vnops.c Tue Aug 8 10:45:22 2017 (r322225)
+++ head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vnops.c Tue Aug 8 10:46:51 2017 (r322226)
@@ -1297,7 +1297,6 @@ zfs_get_data(void *arg, lr_write_t *lr, char *buf, zio
uint64_t object = lr->lr_foid;
uint64_t offset = lr->lr_offset;
uint64_t size = lr->lr_length;
- blkptr_t *bp = &lr->lr_blkptr;
dmu_buf_t *db;
zgd_t *zgd;
int error = 0;
@@ -1374,11 +1373,7 @@ zfs_get_data(void *arg, lr_write_t *lr, char *buf, zio
DMU_READ_NO_PREFETCH);
if (error == 0) {
- blkptr_t *obp = dmu_buf_get_blkptr(db);
- if (obp) {
- ASSERT(BP_IS_HOLE(bp));
- *bp = *obp;
- }
+ blkptr_t *bp = &lr->lr_blkptr;
zgd->zgd_db = db;
zgd->zgd_bp = bp;
Modified: head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zvol.c
==============================================================================
--- head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zvol.c Tue Aug 8 10:45:22 2017 (r322225)
+++ head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zvol.c Tue Aug 8 10:46:51 2017 (r322226)
@@ -27,7 +27,7 @@
* Portions Copyright 2010 Robert Milkowski
*
* Copyright 2011 Nexenta Systems, Inc. All rights reserved.
- * Copyright (c) 2012, 2016 by Delphix. All rights reserved.
+ * Copyright (c) 2012, 2017 by Delphix. All rights reserved.
* Copyright (c) 2013, Joyent, Inc. All rights reserved.
* Copyright (c) 2014 Integros [integros.com]
*/
@@ -1340,7 +1340,6 @@ zvol_get_data(void *arg, lr_write_t *lr, char *buf, zi
uint64_t object = ZVOL_OBJ;
uint64_t offset = lr->lr_offset;
uint64_t size = lr->lr_length; /* length of user data */
- blkptr_t *bp = &lr->lr_blkptr;
dmu_buf_t *db;
zgd_t *zgd;
int error;
@@ -1368,11 +1367,7 @@ zvol_get_data(void *arg, lr_write_t *lr, char *buf, zi
error = dmu_buf_hold(os, object, offset, zgd, &db,
DMU_READ_NO_PREFETCH);
if (error == 0) {
- blkptr_t *obp = dmu_buf_get_blkptr(db);
- if (obp) {
- ASSERT(BP_IS_HOLE(bp));
- *bp = *obp;
- }
+ blkptr_t *bp = &lr->lr_blkptr;
zgd->zgd_db = db;
zgd->zgd_bp = bp;
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