[PATCH v1 6/9] zram: identify asynchronous IO's return value

Minchan Kim
2017-06-26T06:54:09Z

For upcoming asynchronous IO like writeback, zram_rw_page should
be aware of that whether requested IO was completed or submitted
successfully, otherwise error.

For the goal, zram_bvec_rw has three return values.

-errno: returns error number
0: IO request is done synchronously
1: IO request is issued successfully.

Signed-off-by: Minchan Kim <minchan@kernel.org>
---
drivers/block/zram/zram_drv.c | 32 ++++++++++++++++++++++++--------
1 file changed, 24 insertions(+), 8 deletions(-)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index e31fef7..896867e2 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -772,7 +772,7 @@ static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec,

static int __zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index)
{
- int ret;
+ int ret = 0;
unsigned long alloced_pages;
unsigned long handle = 0;
unsigned int comp_len = 0;
@@ -876,7 +876,7 @@ static int __zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index)

/* Update stats */
atomic64_inc(&zram->stats.pages_stored);
- return 0;
+ return ret;
}

static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec,
@@ -958,6 +958,11 @@ static void zram_bio_discard(struct zram *zram, u32 index,
}
}

+/*
+ * Returns errno if it has some problem. Otherwise return 0 or 1.
+ * Returns 0 if IO request was done synchronously
+ * Returns 1 if IO request was successfully submitted.
+ */
static int zram_bvec_rw(struct zram *zram, struct bio_vec *bvec, u32 index,
int offset, bool is_write)
{
@@ -979,7 +984,7 @@ static int zram_bvec_rw(struct zram *zram, struct bio_vec *bvec, u32 index,

generic_end_io_acct(rw_acct, &zram->disk->part0, start_time);

- if (unlikely(ret)) {
+ if (unlikely(ret < 0)) {
if (!is_write)
atomic64_inc(&zram->stats.failed_reads);
else
@@ -1072,7 +1077,7 @@ static void zram_slot_free_notify(struct block_device *bdev,
static int zram_rw_page(struct block_device *bdev, sector_t sector,
struct page *page, bool is_write)
{
- int offset, err = -EIO;
+ int offset, ret;
u32 index;
struct zram *zram;
struct bio_vec bv;
@@ -1081,7 +1086,7 @@ static int zram_rw_page(struct block_device *bdev, sector_t sector,

if (!valid_io_request(zram, sector, PAGE_SIZE)) {
atomic64_inc(&zram->stats.invalid_io);
- err = -EINVAL;
+ ret = -EINVAL;
goto out;
}

@@ -1092,7 +1097,7 @@ static int zram_rw_page(struct block_device *bdev, sector_t sector,
bv.bv_len = PAGE_SIZE;
bv.bv_offset = 0;

- err = zram_bvec_rw(zram, &bv, index, offset, is_write);
+ ret = zram_bvec_rw(zram, &bv, index, offset, is_write);
out:
/*
* If I/O fails, just return error(ie, non-zero) without
@@ -1102,9 +1107,20 @@ static int zram_rw_page(struct block_device *bdev, sector_t sector,
* bio->bi_end_io does things to handle the error
* (e.g., SetPageError, set_page_dirty and extra works).
*/
- if (err == 0)
+ if (unlikely(ret < 0))
+ return ret;
+
+ switch (ret) {
+ case 0:
page_endio(page, is_write, 0);
- return err;
+ break;
+ case 1:
+ ret = 0;
+ break;
+ default:
+ WARN_ON(1);
+ }
+ return ret;
}

static void zram_reset_device(struct zram *zram)
--
2.7.4