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Illumos 6214 - zpools going south
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6214 zpools going south
Reviewed by: Igor Kozhukhov <[email protected]>
Reviewed by: George Wilson <[email protected]>
Reviewed by: Dan McDonald <[email protected]>
Reviewed by: Saso Kiselkov <[email protected]>

References:
  https://www.illumos.org/issues/6214
  http://cr.illumos.org/~webrev/sensille/6214_zpools_going_south/

Porting Notes:

Reintroduce b_compress to the l2arc_buf_hdr_t.  In commit b9541d6
the compression flags were moved to the generic b_flags in the
arc_buf_hdr_t.  This is a problem because l2arc_compress_buf()
may manipulate the compression flags and this can only be done
safely under the hash lock which is not held.  See Illumos 6214
for a detailed analysis of the race.

HDR_GET_COMPRESS() macro was removed from arc_buf_info().

Ported-by: Brian Behlendorf <[email protected]>
Closes #3757
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@sensille @behlendorf
sensille authored and behlendorf committed Sep 11, 2015
1 parent 9965059 commit 4e0f33f
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Showing 3 changed files with 16 additions and 34 deletions.
14 changes: 0 additions & 14 deletions include/sys/arc.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -105,20 +105,6 @@ typedef enum arc_flags
/* Flags specifying whether optional hdr struct fields are defined */
ARC_FLAG_HAS_L1HDR = 1 << 17,
ARC_FLAG_HAS_L2HDR = 1 << 18,

/*
* The arc buffer's compression mode is stored in the top 7 bits of the
* flags field, so these dummy flags are included so that MDB can
* interpret the enum properly.
*/
ARC_FLAG_COMPRESS_0 = 1 << 24,
ARC_FLAG_COMPRESS_1 = 1 << 25,
ARC_FLAG_COMPRESS_2 = 1 << 26,
ARC_FLAG_COMPRESS_3 = 1 << 27,
ARC_FLAG_COMPRESS_4 = 1 << 28,
ARC_FLAG_COMPRESS_5 = 1 << 29,
ARC_FLAG_COMPRESS_6 = 1 << 30

} arc_flags_t;

struct arc_buf {
Expand Down
1 change: 1 addition & 0 deletions include/sys/arc_impl.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -187,6 +187,7 @@ typedef struct l2arc_buf_hdr {
/* real alloc'd buffer size depending on b_compress applied */
uint32_t b_hits;
int32_t b_asize;
uint8_t b_compress;

list_node_t b_l2node;
} l2arc_buf_hdr_t;
Expand Down
35 changes: 15 additions & 20 deletions module/zfs/arc.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -677,15 +677,6 @@ static arc_buf_hdr_t arc_eviction_hdr;
#define HDR_HAS_L1HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L1HDR)
#define HDR_HAS_L2HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR)

/* For storing compression mode in b_flags */
#define HDR_COMPRESS_OFFSET 24
#define HDR_COMPRESS_NBITS 7

#define HDR_GET_COMPRESS(hdr) ((enum zio_compress)BF32_GET(hdr->b_flags, \
HDR_COMPRESS_OFFSET, HDR_COMPRESS_NBITS))
#define HDR_SET_COMPRESS(hdr, cmp) BF32_SET(hdr->b_flags, \
HDR_COMPRESS_OFFSET, HDR_COMPRESS_NBITS, (cmp))

/*
* Other sizes
*/
Expand Down Expand Up @@ -1483,7 +1474,7 @@ arc_buf_info(arc_buf_t *ab, arc_buf_info_t *abi, int state_index)
if (l2hdr) {
abi->abi_l2arc_dattr = l2hdr->b_daddr;
abi->abi_l2arc_asize = l2hdr->b_asize;
abi->abi_l2arc_compress = HDR_GET_COMPRESS(hdr);
abi->abi_l2arc_compress = l2hdr->b_compress;
abi->abi_l2arc_hits = l2hdr->b_hits;
}

Expand Down Expand Up @@ -1954,7 +1945,7 @@ arc_buf_l2_cdata_free(arc_buf_hdr_t *hdr)
* separately compressed buffer, so there's nothing to free (it
* points to the same buffer as the arc_buf_t's b_data field).
*/
if (HDR_GET_COMPRESS(hdr) == ZIO_COMPRESS_OFF) {
if (hdr->b_l2hdr.b_compress == ZIO_COMPRESS_OFF) {
hdr->b_l1hdr.b_tmp_cdata = NULL;
return;
}
Expand All @@ -1963,12 +1954,12 @@ arc_buf_l2_cdata_free(arc_buf_hdr_t *hdr)
* There's nothing to free since the buffer was all zero's and
* compressed to a zero length buffer.
*/
if (HDR_GET_COMPRESS(hdr) == ZIO_COMPRESS_EMPTY) {
if (hdr->b_l2hdr.b_compress == ZIO_COMPRESS_EMPTY) {
ASSERT3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL);
return;
}

ASSERT(L2ARC_IS_VALID_COMPRESS(HDR_GET_COMPRESS(hdr)));
ASSERT(L2ARC_IS_VALID_COMPRESS(hdr->b_l2hdr.b_compress));

arc_buf_free_on_write(hdr->b_l1hdr.b_tmp_cdata,
hdr->b_size, zio_data_buf_free);
Expand Down Expand Up @@ -4429,7 +4420,7 @@ arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_done_func_t *done,
(vd = hdr->b_l2hdr.b_dev->l2ad_vdev) != NULL) {
devw = hdr->b_l2hdr.b_dev->l2ad_writing;
addr = hdr->b_l2hdr.b_daddr;
b_compress = HDR_GET_COMPRESS(hdr);
b_compress = hdr->b_l2hdr.b_compress;
b_asize = hdr->b_l2hdr.b_asize;
/*
* Lock out device removal.
Expand Down Expand Up @@ -6037,6 +6028,8 @@ l2arc_read_done(zio_t *zio)
if (cb->l2rcb_compress != ZIO_COMPRESS_OFF)
l2arc_decompress_zio(zio, hdr, cb->l2rcb_compress);
ASSERT(zio->io_data != NULL);
ASSERT3U(zio->io_size, ==, hdr->b_size);
ASSERT3U(BP_GET_LSIZE(&cb->l2rcb_bp), ==, hdr->b_size);

/*
* Check this survived the L2ARC journey.
Expand Down Expand Up @@ -6073,7 +6066,7 @@ l2arc_read_done(zio_t *zio)
ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL);

zio_nowait(zio_read(pio, cb->l2rcb_spa, &cb->l2rcb_bp,
buf->b_data, zio->io_size, arc_read_done, buf,
buf->b_data, hdr->b_size, arc_read_done, buf,
zio->io_priority, cb->l2rcb_flags, &cb->l2rcb_zb));
}
}
Expand Down Expand Up @@ -6381,7 +6374,7 @@ l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz,
* can't access without holding the ARC list locks
* (which we want to avoid during compression/writing)
*/
HDR_SET_COMPRESS(hdr, ZIO_COMPRESS_OFF);
hdr->b_l2hdr.b_compress = ZIO_COMPRESS_OFF;
hdr->b_l2hdr.b_asize = hdr->b_size;
hdr->b_l2hdr.b_hits = 0;
hdr->b_l1hdr.b_tmp_cdata = hdr->b_l1hdr.b_buf->b_data;
Expand Down Expand Up @@ -6587,7 +6580,7 @@ l2arc_compress_buf(arc_buf_hdr_t *hdr)
l2hdr = &hdr->b_l2hdr;

ASSERT(HDR_HAS_L1HDR(hdr));
ASSERT(HDR_GET_COMPRESS(hdr) == ZIO_COMPRESS_OFF);
ASSERT3U(l2hdr->b_compress, ==, ZIO_COMPRESS_OFF);
ASSERT(hdr->b_l1hdr.b_tmp_cdata != NULL);

len = l2hdr->b_asize;
Expand All @@ -6605,7 +6598,7 @@ l2arc_compress_buf(arc_buf_hdr_t *hdr)
if (csize == 0) {
/* zero block, indicate that there's nothing to write */
zio_data_buf_free(cdata, len);
HDR_SET_COMPRESS(hdr, ZIO_COMPRESS_EMPTY);
l2hdr->b_compress = ZIO_COMPRESS_EMPTY;
l2hdr->b_asize = 0;
hdr->b_l1hdr.b_tmp_cdata = NULL;
ARCSTAT_BUMP(arcstat_l2_compress_zeros);
Expand All @@ -6615,7 +6608,7 @@ l2arc_compress_buf(arc_buf_hdr_t *hdr)
* Compression succeeded, we'll keep the cdata around for
* writing and release it afterwards.
*/
HDR_SET_COMPRESS(hdr, ZIO_COMPRESS_LZ4);
l2hdr->b_compress = ZIO_COMPRESS_LZ4;
l2hdr->b_asize = csize;
hdr->b_l1hdr.b_tmp_cdata = cdata;
ARCSTAT_BUMP(arcstat_l2_compress_successes);
Expand Down Expand Up @@ -6702,9 +6695,11 @@ l2arc_decompress_zio(zio_t *zio, arc_buf_hdr_t *hdr, enum zio_compress c)
static void
l2arc_release_cdata_buf(arc_buf_hdr_t *hdr)
{
enum zio_compress comp = HDR_GET_COMPRESS(hdr);
enum zio_compress comp;

ASSERT(HDR_HAS_L1HDR(hdr));
ASSERT(HDR_HAS_L2HDR(hdr));
comp = hdr->b_l2hdr.b_compress;
ASSERT(comp == ZIO_COMPRESS_OFF || L2ARC_IS_VALID_COMPRESS(comp));

if (comp == ZIO_COMPRESS_OFF) {
Expand Down

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