b8d06fca08
Differences between how paging is done on Solaris and Linux can cause deadlocks if KM_SLEEP is used in any the following contexts. * The txg_sync thread * The zvol write/discard threads * The zpl_putpage() VFS callback This is because KM_SLEEP will allow for direct reclaim which may result in the VM calling back in to the filesystem or block layer to write out pages. If a lock is held over this operation the potential exists to deadlock the system. To ensure forward progress all memory allocations in these contexts must us KM_PUSHPAGE which disables performing any I/O to accomplish the memory allocation. Previously, this behavior was acheived by setting PF_MEMALLOC on the thread. However, that resulted in unexpected side effects such as the exhaustion of pages in ZONE_DMA. This approach touchs more of the zfs code, but it is more consistent with the right way to handle these cases under Linux. This is patch lays the ground work for being able to safely revert the following commits which used PF_MEMALLOC:21ade34Disable direct reclaim for z_wr_* threadscfc9a5cFix zpl_writepage() deadlockeec8164Fix ASSERTION(!dsl_pool_sync_context(tx->tx_pool)) Signed-off-by: Richard Yao <ryao@cs.stonybrook.edu> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Issue #726
117 lines
2.6 KiB
C
117 lines
2.6 KiB
C
/*
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* CDDL HEADER START
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*
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* The contents of this file are subject to the terms of the
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* Common Development and Distribution License (the "License").
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* You may not use this file except in compliance with the License.
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*
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* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
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* or http://www.opensolaris.org/os/licensing.
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* See the License for the specific language governing permissions
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* and limitations under the License.
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*
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* When distributing Covered Code, include this CDDL HEADER in each
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* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
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* If applicable, add the following below this CDDL HEADER, with the
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* fields enclosed by brackets "[]" replaced with your own identifying
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* information: Portions Copyright [yyyy] [name of copyright owner]
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*
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* CDDL HEADER END
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*/
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/*
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* Copyright 2007 Sun Microsystems, Inc. All rights reserved.
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* Use is subject to license terms.
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*/
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#include <sys/zfs_context.h>
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#include <sys/avl.h>
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#include <sys/unique.h>
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static avl_tree_t unique_avl;
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static kmutex_t unique_mtx;
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typedef struct unique {
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avl_node_t un_link;
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uint64_t un_value;
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} unique_t;
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#define UNIQUE_MASK ((1ULL << UNIQUE_BITS) - 1)
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static int
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unique_compare(const void *a, const void *b)
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{
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const unique_t *una = a;
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const unique_t *unb = b;
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if (una->un_value < unb->un_value)
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return (-1);
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if (una->un_value > unb->un_value)
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return (+1);
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return (0);
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}
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void
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unique_init(void)
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{
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avl_create(&unique_avl, unique_compare,
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sizeof (unique_t), offsetof(unique_t, un_link));
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mutex_init(&unique_mtx, NULL, MUTEX_DEFAULT, NULL);
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}
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void
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unique_fini(void)
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{
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avl_destroy(&unique_avl);
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mutex_destroy(&unique_mtx);
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}
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uint64_t
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unique_create(void)
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{
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uint64_t value = unique_insert(0);
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unique_remove(value);
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return (value);
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}
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uint64_t
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unique_insert(uint64_t value)
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{
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avl_index_t idx;
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unique_t *un = kmem_alloc(sizeof (unique_t), KM_PUSHPAGE);
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un->un_value = value;
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mutex_enter(&unique_mtx);
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while (un->un_value == 0 || un->un_value & ~UNIQUE_MASK ||
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avl_find(&unique_avl, un, &idx)) {
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mutex_exit(&unique_mtx);
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(void) random_get_pseudo_bytes((void*)&un->un_value,
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sizeof (un->un_value));
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un->un_value &= UNIQUE_MASK;
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mutex_enter(&unique_mtx);
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}
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avl_insert(&unique_avl, un, idx);
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mutex_exit(&unique_mtx);
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return (un->un_value);
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}
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void
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unique_remove(uint64_t value)
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{
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unique_t un_tofind;
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unique_t *un;
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un_tofind.un_value = value;
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mutex_enter(&unique_mtx);
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un = avl_find(&unique_avl, &un_tofind, NULL);
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if (un != NULL) {
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avl_remove(&unique_avl, un);
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kmem_free(un, sizeof (unique_t));
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}
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mutex_exit(&unique_mtx);
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}
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