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Fix the L2ARC write size calculating logic #14939

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Jun 6, 2023
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45 changes: 29 additions & 16 deletions module/zfs/arc.c
Original file line number Diff line number Diff line change
@@ -965,7 +965,7 @@ static void l2arc_hdr_restore(const l2arc_log_ent_phys_t *le,
l2arc_dev_t *dev);

/* L2ARC persistence write I/O routines. */
static void l2arc_log_blk_commit(l2arc_dev_t *dev, zio_t *pio,
static uint64_t l2arc_log_blk_commit(l2arc_dev_t *dev, zio_t *pio,
l2arc_write_callback_t *cb);

/* L2ARC persistence auxiliary routines. */
@@ -8175,7 +8175,7 @@ l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *hdr)
static uint64_t
l2arc_write_size(l2arc_dev_t *dev)
{
uint64_t size, dev_size, tsize;
uint64_t size;

/*
* Make sure our globals have meaningful values in case the user
@@ -8192,35 +8192,40 @@ l2arc_write_size(l2arc_dev_t *dev)
if (arc_warm == B_FALSE)
size += l2arc_write_boost;

/*
* Make sure the write size does not exceed the size of the cache
* device. This is important in l2arc_evict(), otherwise infinite
* iteration can occur.
*/
dev_size = dev->l2ad_end - dev->l2ad_start;

/* We need to add in the worst case scenario of log block overhead. */
tsize = size + l2arc_log_blk_overhead(size, dev);
size += l2arc_log_blk_overhead(size, dev);
if (dev->l2ad_vdev->vdev_has_trim && l2arc_trim_ahead > 0) {
/*
* Trim ahead of the write size 64MB or (l2arc_trim_ahead/100)
* times the writesize, whichever is greater.
*/
tsize += MAX(64 * 1024 * 1024,
(tsize * l2arc_trim_ahead) / 100);
size += MAX(64 * 1024 * 1024,
(size * l2arc_trim_ahead) / 100);
}

if (tsize >= dev_size) {
/*
* Make sure the write size does not exceed the size of the cache
* device. This is important in l2arc_evict(), otherwise infinite
* iteration can occur.
*/
if (size >= dev->l2ad_end - dev->l2ad_start) {
cmn_err(CE_NOTE, "l2arc_write_max or l2arc_write_boost "
"plus the overhead of log blocks (persistent L2ARC, "
"%llu bytes) exceeds the size of the cache device "
"(guid %llu), resetting them to the default (%d)",
(u_longlong_t)l2arc_log_blk_overhead(size, dev),
(u_longlong_t)dev->l2ad_vdev->vdev_guid, L2ARC_WRITE_SIZE);

size = l2arc_write_max = l2arc_write_boost = L2ARC_WRITE_SIZE;

if (arc_warm == B_FALSE)
size += l2arc_write_boost;

size += l2arc_log_blk_overhead(size, dev);
if (dev->l2ad_vdev->vdev_has_trim && l2arc_trim_ahead > 0) {
size += MAX(64 * 1024 * 1024,
(size * l2arc_trim_ahead) / 100);
}
}

return (size);
@@ -9413,8 +9418,14 @@ l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz)
* arcstat_l2_{size,asize} kstats are updated
* internally.
*/
if (l2arc_log_blk_insert(dev, hdr))
l2arc_log_blk_commit(dev, pio, cb);
if (l2arc_log_blk_insert(dev, hdr)) {
/*
* l2ad_hand has been accounted for in
* l2arc_log_blk_commit().
*/
write_asize +=
l2arc_log_blk_commit(dev, pio, cb);
}

zio_nowait(wzio);
}
@@ -10564,7 +10575,7 @@ l2arc_dev_hdr_update(l2arc_dev_t *dev)
* This function allocates some memory to temporarily hold the serialized
* buffer to be written. This is then released in l2arc_write_done.
*/
static void
static uint64_t
l2arc_log_blk_commit(l2arc_dev_t *dev, zio_t *pio, l2arc_write_callback_t *cb)
{
l2arc_log_blk_phys_t *lb = &dev->l2ad_log_blk;
@@ -10675,6 +10686,8 @@ l2arc_log_blk_commit(l2arc_dev_t *dev, zio_t *pio, l2arc_write_callback_t *cb)
dev->l2ad_log_ent_idx = 0;
dev->l2ad_log_blk_payload_asize = 0;
dev->l2ad_log_blk_payload_start = 0;

return (asize);
}

/*