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Fix read errors race after block cloning #16052

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merged 1 commit into from
Apr 8, 2024
Merged

Fix read errors race after block cloning #16052

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41 changes: 20 additions & 21 deletions module/zfs/dbuf.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1564,7 +1564,7 @@ dbuf_read_impl(dmu_buf_impl_t *db, zio_t *zio, uint32_t flags,
zbookmark_phys_t zb;
uint32_t aflags = ARC_FLAG_NOWAIT;
int err, zio_flags;
blkptr_t bp, *bpp;
blkptr_t bp, *bpp = NULL;

DB_DNODE_ENTER(db);
dn = DB_DNODE(db);
Expand All @@ -1580,29 +1580,28 @@ dbuf_read_impl(dmu_buf_impl_t *db, zio_t *zio, uint32_t flags,
goto early_unlock;
}

if (db->db_state == DB_UNCACHED) {
if (db->db_blkptr == NULL) {
bpp = NULL;
} else {
bp = *db->db_blkptr;
/*
* If we have a pending block clone, we don't want to read the
* underlying block, but the content of the block being cloned,
* pointed by the dirty record, so we have the most recent data.
* If there is no dirty record, then we hit a race in a sync
* process when the dirty record is already removed, while the
* dbuf is not yet destroyed. Such case is equivalent to uncached.
*/
if (db->db_state == DB_NOFILL) {
dbuf_dirty_record_t *dr = list_head(&db->db_dirty_records);
if (dr != NULL) {
if (!dr->dt.dl.dr_brtwrite) {
err = EIO;
goto early_unlock;
}
bp = dr->dt.dl.dr_overridden_by;
bpp = &bp;
}
} else {
dbuf_dirty_record_t *dr;

ASSERT3S(db->db_state, ==, DB_NOFILL);
}

/*
* Block cloning: If we have a pending block clone,
* we don't want to read the underlying block, but the content
* of the block being cloned, so we have the most recent data.
*/
dr = list_head(&db->db_dirty_records);
if (dr == NULL || !dr->dt.dl.dr_brtwrite) {
err = EIO;
goto early_unlock;
}
bp = dr->dt.dl.dr_overridden_by;
if (bpp == NULL && db->db_blkptr != NULL) {
bp = *db->db_blkptr;
bpp = &bp;
}

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