From fa7e0e5a6cf25a857470eb51b5844d010169687e Mon Sep 17 00:00:00 2001 From: avg Date: Fri, 14 Apr 2017 18:09:32 +0000 Subject: [PATCH] 7580 ztest failure in dbuf_read_impl illumos/illumos-gate@1a01181fdc809f40c64d5c6881ae3e4521a9d9c7 https://github.com/illumos/illumos-gate/commit/1a01181fdc809f40c64d5c6881ae3e4521a9d9c7 https://www.illumos.org/issues/7580 We need to prevent any reader whenever we're about the zero out all the blkptrs. To do this we need to grab the dn_struct_rwlock as writer in dbuf_write_children_ready and free_children just prior to calling bzero. Reviewed by: Pavel Zakharov Reviewed by: Steve Gonczi Reviewed by: Matthew Ahrens Approved by: Dan McDonald Author: George Wilson --- uts/common/fs/zfs/dbuf.c | 12 +++++++++--- uts/common/fs/zfs/dnode_sync.c | 17 ++++++++++++----- 2 files changed, 21 insertions(+), 8 deletions(-) diff --git a/uts/common/fs/zfs/dbuf.c b/uts/common/fs/zfs/dbuf.c index 2879bd387182..aa06c7c2187c 100644 --- a/uts/common/fs/zfs/dbuf.c +++ b/uts/common/fs/zfs/dbuf.c @@ -3313,13 +3313,13 @@ dbuf_write_children_ready(zio_t *zio, arc_buf_t *buf, void *vdb) dmu_buf_impl_t *db = vdb; dnode_t *dn; blkptr_t *bp; - uint64_t i; - int epbs; + unsigned int epbs, i; ASSERT3U(db->db_level, >, 0); DB_DNODE_ENTER(db); dn = DB_DNODE(db); epbs = dn->dn_phys->dn_indblkshift - SPA_BLKPTRSHIFT; + ASSERT3U(epbs, <, 31); /* Determine if all our children are holes */ for (i = 0, bp = db->db.db_data; i < 1 << epbs; i++, bp++) { @@ -3332,8 +3332,14 @@ dbuf_write_children_ready(zio_t *zio, arc_buf_t *buf, void *vdb) * we may get compressed away. */ if (i == 1 << epbs) { - /* didn't find any non-holes */ + /* + * We only found holes. Grab the rwlock to prevent + * anybody from reading the blocks we're about to + * zero out. + */ + rw_enter(&dn->dn_struct_rwlock, RW_WRITER); bzero(db->db.db_data, db->db.db_size); + rw_exit(&dn->dn_struct_rwlock); } DB_DNODE_EXIT(db); } diff --git a/uts/common/fs/zfs/dnode_sync.c b/uts/common/fs/zfs/dnode_sync.c index 760915d8f383..a17414c0d4ba 100644 --- a/uts/common/fs/zfs/dnode_sync.c +++ b/uts/common/fs/zfs/dnode_sync.c @@ -236,8 +236,8 @@ free_children(dmu_buf_impl_t *db, uint64_t blkid, uint64_t nblks, dnode_t *dn; blkptr_t *bp; dmu_buf_impl_t *subdb; - uint64_t start, end, dbstart, dbend, i; - int epbs, shift; + uint64_t start, end, dbstart, dbend; + unsigned int epbs, shift, i; /* * There is a small possibility that this block will not be cached: @@ -254,6 +254,7 @@ free_children(dmu_buf_impl_t *db, uint64_t blkid, uint64_t nblks, DB_DNODE_ENTER(db); dn = DB_DNODE(db); epbs = dn->dn_phys->dn_indblkshift - SPA_BLKPTRSHIFT; + ASSERT3U(epbs, <, 31); shift = (db->db_level - 1) * epbs; dbstart = db->db_blkid << epbs; start = blkid >> shift; @@ -273,12 +274,12 @@ free_children(dmu_buf_impl_t *db, uint64_t blkid, uint64_t nblks, FREE_VERIFY(db, start, end, tx); free_blocks(dn, bp, end-start+1, tx); } else { - for (i = start; i <= end; i++, bp++) { + for (uint64_t id = start; id <= end; id++, bp++) { if (BP_IS_HOLE(bp)) continue; rw_enter(&dn->dn_struct_rwlock, RW_READER); VERIFY0(dbuf_hold_impl(dn, db->db_level - 1, - i, TRUE, FALSE, FTAG, &subdb)); + id, TRUE, FALSE, FTAG, &subdb)); rw_exit(&dn->dn_struct_rwlock); ASSERT3P(bp, ==, subdb->db_blkptr); @@ -293,8 +294,14 @@ free_children(dmu_buf_impl_t *db, uint64_t blkid, uint64_t nblks, break; } if (i == 1 << epbs) { - /* didn't find any non-holes */ + /* + * We only found holes. Grab the rwlock to prevent + * anybody from reading the blocks we're about to + * zero out. + */ + rw_enter(&dn->dn_struct_rwlock, RW_WRITER); bzero(db->db.db_data, db->db.db_size); + rw_exit(&dn->dn_struct_rwlock); free_blocks(dn, db->db_blkptr, 1, tx); } else { /*