* Copyright (c) 2009, 2010, Oracle and/or its affiliates. All rights reserved.
* Use is subject to license terms.
*
- * Copyright (c) 2012, 2015, Intel Corporation.
+ * Copyright (c) 2012, 2016, Intel Corporation.
*/
/*
* This file is part of Lustre, http://www.lustre.org/
(void)osd_grow_blocksize(obj, oh, lnb[0].lnb_file_offset,
lnb[npages - 1].lnb_file_offset +
lnb[npages - 1].lnb_len);
+
+ /* LU-8791: take oo_guard to avoid the deadlock that changing block
+ * size and assigning arcbuf take place at the same time.
+ *
+ * Thread 1:
+ * osd_write_commit()
+ * -> osd_grow_blocksize() with osd_object::oo_guard held
+ * -> dmu_object_set_blocksize()
+ * -> dnode_set_blksz(), with dnode_t::dn_struct_rwlock
+ * write lock held
+ * -> dbuf_new_size()
+ * -> dmu_buf_will_dirty()
+ * -> dbuf_read()
+ * -> wait for the dbuf state to change
+ * Thread 2:
+ * osd_write_commit()
+ * -> dmu_assign_arcbuf()
+ * -> dbuf_assign_arcbuf(), set dbuf state to DB_FILL
+ * -> dbuf_dirty()
+ * -> try to hold the read lock of dnode_t::dn_struct_rwlock
+ *
+ * By taking the read lock, it can avoid thread 2 to enter into the
+ * critical section of assigning the arcbuf, while thread 1 is
+ * changing the block size.
+ */
+ down_read(&obj->oo_guard);
for (i = 0; i < npages; i++) {
CDEBUG(D_INODE, "write %u bytes at %u\n",
(unsigned) lnb[i].lnb_len,
new_size = lnb[i].lnb_file_offset + lnb[i].lnb_len;
iosize += lnb[i].lnb_len;
}
+ up_read(&obj->oo_guard);
if (unlikely(new_size == 0)) {
/* no pages to write, no transno is needed */