Date: Fri, 5 Dec 2014 00:32:33 +0000 (UTC) From: Xin LI <delphij@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-10@freebsd.org Subject: svn commit: r275492 - stable/10/sys/cddl/contrib/opensolaris/uts/common/fs/zfs Message-ID: <201412050032.sB50WXki040350@svn.freebsd.org>
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Author: delphij Date: Fri Dec 5 00:32:33 2014 New Revision: 275492 URL: https://svnweb.freebsd.org/changeset/base/275492 Log: MFC r274172 (avg) fix l2arc compression buffers leak We have observed that arc_release() can be called concurrently with a l2arc in-flight write. Also, we have observed that arc_hdr_destroy() can be called from arc_write_done() for a zio with ZIO_FLAG_IO_REWRITE flag in similar circumstances. Previously the l2arc headers would be freed while leaking their associated compression buffers. Now the buffers are placed on l2arc_free_on_write list for delayed freeing. This is similar to what was already done to arc buffers that were supposed to be freed concurrently with in-flight writes of those buffers. In addition to fixing the discovered leaks this change also adds some protective code to assert that a compression buffer associated with a l2arc header is never leaked. A new kstat l2_cdata_free_on_write is added. It keeps a count of delayed compression buffer frees which previously would have been leaks. Tested by: Vitalij Satanivskij <satan@ukr.net> et al Requested by: many Sponsored by: HybridCluster / ClusterHQ This is a 10.1-RELEASE errata candidate. Modified: stable/10/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/arc.c Directory Properties: stable/10/ (props changed) Modified: stable/10/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/arc.c ============================================================================== --- stable/10/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/arc.c Thu Dec 4 23:27:29 2014 (r275491) +++ stable/10/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/arc.c Fri Dec 5 00:32:33 2014 (r275492) @@ -390,6 +390,7 @@ typedef struct arc_stats { kstat_named_t arcstat_l2_evict_lock_retry; kstat_named_t arcstat_l2_evict_reading; kstat_named_t arcstat_l2_free_on_write; + kstat_named_t arcstat_l2_cdata_free_on_write; kstat_named_t arcstat_l2_abort_lowmem; kstat_named_t arcstat_l2_cksum_bad; kstat_named_t arcstat_l2_io_error; @@ -467,6 +468,7 @@ static arc_stats_t arc_stats = { { "l2_evict_lock_retry", KSTAT_DATA_UINT64 }, { "l2_evict_reading", KSTAT_DATA_UINT64 }, { "l2_free_on_write", KSTAT_DATA_UINT64 }, + { "l2_cdata_free_on_write", KSTAT_DATA_UINT64 }, { "l2_abort_lowmem", KSTAT_DATA_UINT64 }, { "l2_cksum_bad", KSTAT_DATA_UINT64 }, { "l2_io_error", KSTAT_DATA_UINT64 }, @@ -1658,6 +1660,21 @@ arc_buf_add_ref(arc_buf_t *buf, void* ta data, metadata, hits); } +static void +arc_buf_free_on_write(void *data, size_t size, + void (*free_func)(void *, size_t)) +{ + l2arc_data_free_t *df; + + df = kmem_alloc(sizeof (l2arc_data_free_t), KM_SLEEP); + df->l2df_data = data; + df->l2df_size = size; + df->l2df_func = free_func; + mutex_enter(&l2arc_free_on_write_mtx); + list_insert_head(l2arc_free_on_write, df); + mutex_exit(&l2arc_free_on_write_mtx); +} + /* * Free the arc data buffer. If it is an l2arc write in progress, * the buffer is placed on l2arc_free_on_write to be freed later. @@ -1668,14 +1685,7 @@ arc_buf_data_free(arc_buf_t *buf, void ( arc_buf_hdr_t *hdr = buf->b_hdr; if (HDR_L2_WRITING(hdr)) { - l2arc_data_free_t *df; - df = kmem_alloc(sizeof (l2arc_data_free_t), KM_SLEEP); - df->l2df_data = buf->b_data; - df->l2df_size = hdr->b_size; - df->l2df_func = free_func; - mutex_enter(&l2arc_free_on_write_mtx); - list_insert_head(l2arc_free_on_write, df); - mutex_exit(&l2arc_free_on_write_mtx); + arc_buf_free_on_write(buf->b_data, hdr->b_size, free_func); ARCSTAT_BUMP(arcstat_l2_free_on_write); } else { free_func(buf->b_data, hdr->b_size); @@ -1687,6 +1697,23 @@ arc_buf_data_free(arc_buf_t *buf, void ( * arc_buf_t off of the the arc_buf_hdr_t's list and free it. */ static void +arc_buf_l2_cdata_free(arc_buf_hdr_t *hdr) +{ + l2arc_buf_hdr_t *l2hdr = hdr->b_l2hdr; + + ASSERT(MUTEX_HELD(&l2arc_buflist_mtx)); + + if (l2hdr->b_tmp_cdata == NULL) + return; + + ASSERT(HDR_L2_WRITING(hdr)); + arc_buf_free_on_write(l2hdr->b_tmp_cdata, hdr->b_size, + zio_data_buf_free); + ARCSTAT_BUMP(arcstat_l2_cdata_free_on_write); + l2hdr->b_tmp_cdata = NULL; +} + +static void arc_buf_destroy(arc_buf_t *buf, boolean_t recycle, boolean_t remove) { arc_buf_t **bufp; @@ -1785,6 +1812,7 @@ arc_hdr_destroy(arc_buf_hdr_t *hdr) trim_map_free(l2hdr->b_dev->l2ad_vdev, l2hdr->b_daddr, hdr->b_size, 0); list_remove(l2hdr->b_dev->l2ad_buflist, hdr); + arc_buf_l2_cdata_free(hdr); ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size); ARCSTAT_INCR(arcstat_l2_asize, -l2hdr->b_asize); vdev_space_update(l2hdr->b_dev->l2ad_vdev, @@ -3678,6 +3706,7 @@ arc_release(arc_buf_t *buf, void *tag) l2hdr = hdr->b_l2hdr; if (l2hdr) { mutex_enter(&l2arc_buflist_mtx); + arc_buf_l2_cdata_free(hdr); hdr->b_l2hdr = NULL; list_remove(l2hdr->b_dev->l2ad_buflist, hdr); } @@ -4967,6 +4996,11 @@ top: ARCSTAT_INCR(arcstat_l2_asize, -abl2->b_asize); bytes_evicted += abl2->b_asize; ab->b_l2hdr = NULL; + /* + * We are destroying l2hdr, so ensure that + * its compressed buffer, if any, is not leaked. + */ + ASSERT(abl2->b_tmp_cdata == NULL); kmem_free(abl2, sizeof (l2arc_buf_hdr_t)); ARCSTAT_INCR(arcstat_l2_size, -ab->b_size); } @@ -5205,6 +5239,14 @@ l2arc_write_buffers(spa_t *spa, l2arc_de buf_data = l2hdr->b_tmp_cdata; buf_sz = l2hdr->b_asize; + /* + * If the data has not been compressed, then clear b_tmp_cdata + * to make sure that it points only to a temporary compression + * buffer. + */ + if (!L2ARC_IS_VALID_COMPRESS(l2hdr->b_compress)) + l2hdr->b_tmp_cdata = NULL; + /* Compression may have squashed the buffer to zero length. */ if (buf_sz != 0) { uint64_t buf_p_sz; @@ -5395,15 +5437,18 @@ l2arc_release_cdata_buf(arc_buf_hdr_t *a { l2arc_buf_hdr_t *l2hdr = ab->b_l2hdr; - if (l2hdr->b_compress == ZIO_COMPRESS_LZ4) { + ASSERT(L2ARC_IS_VALID_COMPRESS(l2hdr->b_compress)); + if (l2hdr->b_compress != ZIO_COMPRESS_EMPTY) { /* * If the data was compressed, then we've allocated a * temporary buffer for it, so now we need to release it. */ ASSERT(l2hdr->b_tmp_cdata != NULL); zio_data_buf_free(l2hdr->b_tmp_cdata, ab->b_size); + l2hdr->b_tmp_cdata = NULL; + } else { + ASSERT(l2hdr->b_tmp_cdata == NULL); } - l2hdr->b_tmp_cdata = NULL; } /*
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