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Date: Mon, 11 Sep 2023 15:34:27 +0200
From: Pankaj Raghav <kernel@...kajraghav.com>
To: minchan@...nel.org, senozhatsky@...omium.org
Cc: linux-kernel@...r.kernel.org, axboe@...nel.dk,
p.raghav@...sung.com, linux-block@...r.kernel.org,
kernel@...kajraghav.com, gost.dev@...sung.com
Subject: [PATCH 2/5] zram: encapsulate writeback to the backing bdev in a function
From: Pankaj Raghav <p.raghav@...sung.com>
Encapsulate the flushing data to the backing bdev in writeback in a
separate function writeback_flush_to_bdev(). This is in preparation for
adding batching IO support to writeback_store().
No functional changes.
Signed-off-by: Pankaj Raghav <p.raghav@...sung.com>
---
drivers/block/zram/zram_drv.c | 125 ++++++++++++++++++----------------
1 file changed, 68 insertions(+), 57 deletions(-)
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index eaf9e227778e..bd93ed653b99 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -635,14 +635,78 @@ static bool writeback_prep_or_skip_index(struct zram *zram, int mode,
return ret;
}
+static int writeback_flush_to_bdev(struct zram *zram, unsigned long index,
+ struct page *page, unsigned long *blk_idx)
+{
+ struct bio bio;
+ struct bio_vec bio_vec;
+ int ret;
+
+ bio_init(&bio, zram->bdev, &bio_vec, 1, REQ_OP_WRITE | REQ_SYNC);
+ bio.bi_iter.bi_sector = *blk_idx * (PAGE_SIZE >> 9);
+ __bio_add_page(&bio, page, PAGE_SIZE, 0);
+
+ /*
+ * XXX: A single page IO would be inefficient for write
+ * but it would be not bad as starter.
+ */
+ ret = submit_bio_wait(&bio);
+ if (ret) {
+ zram_slot_lock(zram, index);
+ zram_clear_flag(zram, index, ZRAM_UNDER_WB);
+ zram_clear_flag(zram, index, ZRAM_IDLE);
+ zram_slot_unlock(zram, index);
+ /*
+ * BIO errors are not fatal, we continue and simply
+ * attempt to writeback the remaining objects (pages).
+ * At the same time we need to signal user-space that
+ * some writes (at least one, but also could be all of
+ * them) were not successful and we do so by returning
+ * the most recent BIO error.
+ */
+ return ret;
+ }
+
+ atomic64_inc(&zram->stats.bd_writes);
+ /*
+ * We released zram_slot_lock so need to check if the slot was
+ * changed. If there is freeing for the slot, we can catch it
+ * easily by zram_allocated.
+ * A subtle case is the slot is freed/reallocated/marked as
+ * ZRAM_IDLE again. To close the race, idle_store doesn't
+ * mark ZRAM_IDLE once it found the slot was ZRAM_UNDER_WB.
+ * Thus, we could close the race by checking ZRAM_IDLE bit.
+ */
+ zram_slot_lock(zram, index);
+ if (!zram_allocated(zram, index) ||
+ !zram_test_flag(zram, index, ZRAM_IDLE)) {
+ zram_clear_flag(zram, index, ZRAM_UNDER_WB);
+ zram_clear_flag(zram, index, ZRAM_IDLE);
+ goto skip;
+ }
+
+ zram_free_page(zram, index);
+ zram_clear_flag(zram, index, ZRAM_UNDER_WB);
+ zram_set_flag(zram, index, ZRAM_WB);
+ zram_set_element(zram, index, *blk_idx);
+ atomic64_inc(&zram->stats.pages_stored);
+ *blk_idx = 0;
+
+ spin_lock(&zram->wb_limit_lock);
+ if (zram->wb_limit_enable && zram->bd_wb_limit > 0)
+ zram->bd_wb_limit -= 1UL << (PAGE_SHIFT - 12);
+ spin_unlock(&zram->wb_limit_lock);
+skip:
+ zram_slot_unlock(zram, index);
+ return 0;
+}
+
static ssize_t writeback_store(struct device *dev,
struct device_attribute *attr, const char *buf, size_t len)
{
struct zram *zram = dev_to_zram(dev);
unsigned long nr_pages = zram->disksize >> PAGE_SHIFT;
unsigned long index = 0;
- struct bio bio;
- struct bio_vec bio_vec;
struct page *page;
ssize_t ret = len;
int mode, err;
@@ -713,63 +777,10 @@ static ssize_t writeback_store(struct device *dev,
continue;
}
- bio_init(&bio, zram->bdev, &bio_vec, 1,
- REQ_OP_WRITE | REQ_SYNC);
- bio.bi_iter.bi_sector = blk_idx * (PAGE_SIZE >> 9);
- __bio_add_page(&bio, page, PAGE_SIZE, 0);
+ err = writeback_flush_to_bdev(zram, index, page, &blk_idx);
- /*
- * XXX: A single page IO would be inefficient for write
- * but it would be not bad as starter.
- */
- err = submit_bio_wait(&bio);
- if (err) {
- zram_slot_lock(zram, index);
- zram_clear_flag(zram, index, ZRAM_UNDER_WB);
- zram_clear_flag(zram, index, ZRAM_IDLE);
- zram_slot_unlock(zram, index);
- /*
- * BIO errors are not fatal, we continue and simply
- * attempt to writeback the remaining objects (pages).
- * At the same time we need to signal user-space that
- * some writes (at least one, but also could be all of
- * them) were not successful and we do so by returning
- * the most recent BIO error.
- */
+ if (err)
ret = err;
- continue;
- }
-
- atomic64_inc(&zram->stats.bd_writes);
- /*
- * We released zram_slot_lock so need to check if the slot was
- * changed. If there is freeing for the slot, we can catch it
- * easily by zram_allocated.
- * A subtle case is the slot is freed/reallocated/marked as
- * ZRAM_IDLE again. To close the race, idle_store doesn't
- * mark ZRAM_IDLE once it found the slot was ZRAM_UNDER_WB.
- * Thus, we could close the race by checking ZRAM_IDLE bit.
- */
- zram_slot_lock(zram, index);
- if (!zram_allocated(zram, index) ||
- !zram_test_flag(zram, index, ZRAM_IDLE)) {
- zram_clear_flag(zram, index, ZRAM_UNDER_WB);
- zram_clear_flag(zram, index, ZRAM_IDLE);
- goto next;
- }
-
- zram_free_page(zram, index);
- zram_clear_flag(zram, index, ZRAM_UNDER_WB);
- zram_set_flag(zram, index, ZRAM_WB);
- zram_set_element(zram, index, blk_idx);
- blk_idx = 0;
- atomic64_inc(&zram->stats.pages_stored);
- spin_lock(&zram->wb_limit_lock);
- if (zram->wb_limit_enable && zram->bd_wb_limit > 0)
- zram->bd_wb_limit -= 1UL << (PAGE_SHIFT - 12);
- spin_unlock(&zram->wb_limit_lock);
-next:
- zram_slot_unlock(zram, index);
}
if (blk_idx)
--
2.40.1
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