BACKPORT: zram: remove waitqueue for IO done

zram_reset_device() waits for ongoing writepage pages to be completed by
zram->refcount logic.  However, it's pointless because before the reset,
we prevent further opening of zram by zram->claim and flush all of
pending IO by fsync_bdev so there should be no pending IO at the
zram_reset_device().

So let's remove that code which is even broken due to the lack of
wake_up elsewhere.

Link: http://lkml.kernel.org/r/1485145031-11661-1-git-send-email-minchan@kernel.org
Signed-off-by: Minchan Kim <minchan@kernel.org>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
(cherry picked from commit a09759acaacf6cf738e1bc6c66d41485c87fd371)
Signed-off-by: Peter Kalauskas <peskal@google.com>
Bug: 112488418
Change-Id: I97170fb576be7baae63f82334af0dd5e91b16763

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 022cda34ef34843463d7836fc56959696981e16e..c4cd527bc66c14328db251badb13b40381f134ec 100644 (file)
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -390,18 +390,6 @@ static DEVICE_ATTR_RO(io_stat);
 static DEVICE_ATTR_RO(mm_stat);
 static DEVICE_ATTR_RO(debug_stat);
 
-static inline bool zram_meta_get(struct zram *zram)
-{
-       if (atomic_inc_not_zero(&zram->refcount))
-               return true;
-       return false;
-}
-
-static inline void zram_meta_put(struct zram *zram)
-{
-       atomic_dec(&zram->refcount);
-}
-
 static void zram_meta_free(struct zram_meta *meta, u64 disksize)
 {
        size_t num_pages = disksize >> PAGE_SHIFT;
@@ -855,22 +843,17 @@ static blk_qc_t zram_make_request(struct request_queue *queue, struct bio *bio)
 {
        struct zram *zram = queue->queuedata;
 
-       if (unlikely(!zram_meta_get(zram)))
-               goto error;
-
        blk_queue_split(queue, &bio, queue->bio_split);
 
        if (!valid_io_request(zram, bio->bi_iter.bi_sector,
                                        bio->bi_iter.bi_size)) {
                atomic64_inc(&zram->stats.invalid_io);
-               goto put_zram;
+               goto error;
        }
 
        __zram_make_request(zram, bio);
-       zram_meta_put(zram);
        return BLK_QC_T_NONE;
-put_zram:
-       zram_meta_put(zram);
+
 error:
        bio_io_error(bio);
        return BLK_QC_T_NONE;
@@ -900,13 +883,11 @@ static int zram_rw_page(struct block_device *bdev, sector_t sector,
        struct bio_vec bv;
 
        zram = bdev->bd_disk->private_data;
-       if (unlikely(!zram_meta_get(zram)))
-               goto out;
 
        if (!valid_io_request(zram, sector, PAGE_SIZE)) {
                atomic64_inc(&zram->stats.invalid_io);
                err = -EINVAL;
-               goto put_zram;
+               goto out;
        }
 
        index = sector >> SECTORS_PER_PAGE_SHIFT;
@@ -917,8 +898,6 @@ static int zram_rw_page(struct block_device *bdev, sector_t sector,
        bv.bv_offset = 0;
 
        err = zram_bvec_rw(zram, &bv, index, offset, rw);
-put_zram:
-       zram_meta_put(zram);
 out:
        /*
         * If I/O fails, just return error(ie, non-zero) without
@@ -951,17 +930,6 @@ static void zram_reset_device(struct zram *zram)
        meta = zram->meta;
        comp = zram->comp;
        disksize = zram->disksize;
-       /*
-        * Refcount will go down to 0 eventually and r/w handler
-        * cannot handle further I/O so it will bail out by
-        * check zram_meta_get.
-        */
-       zram_meta_put(zram);
-       /*
-        * We want to free zram_meta in process context to avoid
-        * deadlock between reclaim path and any other locks.
-        */
-       wait_event(zram->io_done, atomic_read(&zram->refcount) == 0);
 
        /* Reset stats */
        memset(&zram->stats, 0, sizeof(zram->stats));
@@ -1009,8 +977,6 @@ static ssize_t disksize_store(struct device *dev,
                goto out_destroy_comp;
        }
 
-       init_waitqueue_head(&zram->io_done);
-       atomic_set(&zram->refcount, 1);
        zram->meta = meta;
        zram->comp = comp;
        zram->disksize = disksize;

diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h
index 74fcf10da37499a610d99f3381878b75546ea24d..2692554b773766ee559b1079f364046017facaba 100644 (file)
--- a/drivers/block/zram/zram_drv.h
+++ b/drivers/block/zram/zram_drv.h
@@ -106,9 +106,6 @@ struct zram {
        unsigned long limit_pages;
 
        struct zram_stats stats;
-       atomic_t refcount; /* refcount for zram_meta */
-       /* wait all IO under all of cpu are done */
-       wait_queue_head_t io_done;
        /*
         * This is the limit on amount of *uncompressed* worth of data
         * we can store in a disk.