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fix l2arc compression buffers leak

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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
MFC after:	2 weeks
Sponsored by:	HybridCluster / ClusterHQ
This commit is contained in:
Andriy Gapon 2014-11-06 11:08:02 +00:00
parent 160c039d4e
commit 2fd3cc0cb2
1 changed files with 55 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

65
sys/cddl/contrib/opensolaris/uts/common/fs/zfs/arc.c
View File

@ -387,6 +387,7 @@ 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;
@ -464,6 +465,7 @@ 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 },
@ -1655,6 +1657,21 @@ arc_buf_add_ref(arc_buf_t *buf, void* tag)
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.
@ -1665,14 +1682,7 @@ arc_buf_data_free(arc_buf_t *buf, void (*free_func)(void *, size_t))
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);
@ -1683,6 +1693,23 @@ arc_buf_data_free(arc_buf_t *buf, void (*free_func)(void *, size_t))
* Free up buf->b_data and if 'remove' is set, then pull the
* 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)
{
@ -1782,6 +1809,7 @@ 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,
@ -3675,6 +3703,7 @@ 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);
}
@ -4964,6 +4993,11 @@ l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all)
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);
}
@ -5202,6 +5236,14 @@ l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz,
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;
@ -5392,15 +5434,18 @@ l2arc_release_cdata_buf(arc_buf_hdr_t *ab)
{
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;
}
/*