Re: [PATCH 07/10] fs: make generic file read/write functions plug

From: Jens Axboe
Date: Tue Mar 08 2011 - 07:38:22 EST

On 2011-03-04 14:25, hch@xxxxxxxxxxxxx wrote:
> REQ_UNPLUG should simply go away with the explicit stack plugging.
> What's left for REQ_SYNC? It'll control if the request goes into the
> sync bucket and some cfq tweaks. We should clearly document what it
> does.

How about the below? It gets rid of REQ_UNPLUG.

diff --git a/block/blk-core.c b/block/blk-core.c
index 82a4589..7e9715a 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1290,7 +1290,7 @@ get_rq:
}

plug = current->plug;
- if (plug && !sync) {
+ if (plug) {
if (!plug->should_sort && !list_empty(&plug->list)) {
struct request *__rq;

diff --git a/drivers/block/drbd/drbd_actlog.c b/drivers/block/drbd/drbd_actlog.c
index 2096628..aca3024 100644
--- a/drivers/block/drbd/drbd_actlog.c
+++ b/drivers/block/drbd/drbd_actlog.c
@@ -80,7 +80,7 @@ static int _drbd_md_sync_page_io(struct drbd_conf *mdev,

if ((rw & WRITE) && !test_bit(MD_NO_FUA, &mdev->flags))
rw |= REQ_FUA;
- rw |= REQ_UNPLUG | REQ_SYNC;
+ rw |= REQ_SYNC;

bio = bio_alloc(GFP_NOIO, 1);
bio->bi_bdev = bdev->md_bdev;
diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
index 0b5718e..b0bd27d 100644
--- a/drivers/block/drbd/drbd_int.h
+++ b/drivers/block/drbd/drbd_int.h
@@ -377,7 +377,7 @@ union p_header {
#define DP_HARDBARRIER 1 /* depricated */
#define DP_RW_SYNC 2 /* equals REQ_SYNC */
#define DP_MAY_SET_IN_SYNC 4
-#define DP_UNPLUG 8 /* equals REQ_UNPLUG */
+#define DP_UNPLUG 8 /* not used anymore */
#define DP_FUA 16 /* equals REQ_FUA */
#define DP_FLUSH 32 /* equals REQ_FLUSH */
#define DP_DISCARD 64 /* equals REQ_DISCARD */
diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index 6049cb8..8a43ce0 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -2477,12 +2477,11 @@ static u32 bio_flags_to_wire(struct drbd_conf *mdev, unsigned long bi_rw)
{
if (mdev->agreed_pro_version >= 95)
return (bi_rw & REQ_SYNC ? DP_RW_SYNC : 0) |
- (bi_rw & REQ_UNPLUG ? DP_UNPLUG : 0) |
(bi_rw & REQ_FUA ? DP_FUA : 0) |
(bi_rw & REQ_FLUSH ? DP_FLUSH : 0) |
(bi_rw & REQ_DISCARD ? DP_DISCARD : 0);
else
- return bi_rw & (REQ_SYNC | REQ_UNPLUG) ? DP_RW_SYNC : 0;
+ return bi_rw & REQ_SYNC ? DP_RW_SYNC : 0;
}

/* Used to send write requests
diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
index 84132f8..8e68be9 100644
--- a/drivers/block/drbd/drbd_receiver.c
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -1100,8 +1100,6 @@ next_bio:
/* > e->sector, unless this is the first bio */
bio->bi_sector = sector;
bio->bi_bdev = mdev->ldev->backing_bdev;
- /* we special case some flags in the multi-bio case, see below
- * (REQ_UNPLUG) */
bio->bi_rw = rw;
bio->bi_private = e;
bio->bi_end_io = drbd_endio_sec;
@@ -1130,10 +1128,6 @@ next_bio:
bios = bios->bi_next;
bio->bi_next = NULL;

- /* strip off REQ_UNPLUG unless it is the last bio */
- if (bios)
- bio->bi_rw &= ~REQ_UNPLUG;
-
drbd_generic_make_request(mdev, fault_type, bio);
} while (bios);
return 0;
@@ -1621,12 +1615,11 @@ static unsigned long write_flags_to_bio(struct drbd_conf *mdev, u32 dpf)
{
if (mdev->agreed_pro_version >= 95)
return (dpf & DP_RW_SYNC ? REQ_SYNC : 0) |
- (dpf & DP_UNPLUG ? REQ_UNPLUG : 0) |
(dpf & DP_FUA ? REQ_FUA : 0) |
(dpf & DP_FLUSH ? REQ_FUA : 0) |
(dpf & DP_DISCARD ? REQ_DISCARD : 0);
else
- return dpf & DP_RW_SYNC ? (REQ_SYNC | REQ_UNPLUG) : 0;
+ return dpf & DP_RW_SYNC ? REQ_SYNC : 0;
}

/* mirrored write */
diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
index 54bfc27..ca203cb 100644
--- a/drivers/md/bitmap.c
+++ b/drivers/md/bitmap.c
@@ -347,7 +347,7 @@ static void write_page(struct bitmap *bitmap, struct page *page, int wait)
atomic_inc(&bitmap->pending_writes);
set_buffer_locked(bh);
set_buffer_mapped(bh);
- submit_bh(WRITE | REQ_UNPLUG | REQ_SYNC, bh);
+ submit_bh(WRITE | REQ_SYNC, bh);
bh = bh->b_this_page;
}

diff --git a/drivers/md/dm-io.c b/drivers/md/dm-io.c
index 136d4f7..76a5af0 100644
--- a/drivers/md/dm-io.c
+++ b/drivers/md/dm-io.c
@@ -352,7 +352,7 @@ static void dispatch_io(int rw, unsigned int num_regions,
BUG_ON(num_regions > DM_IO_MAX_REGIONS);

if (sync)
- rw |= REQ_SYNC | REQ_UNPLUG;
+ rw |= REQ_SYNC;

/*
* For multiple regions we need to be careful to rewind
diff --git a/drivers/md/dm-kcopyd.c b/drivers/md/dm-kcopyd.c
index e8429ce..2c880e9 100644
--- a/drivers/md/dm-kcopyd.c
+++ b/drivers/md/dm-kcopyd.c
@@ -363,11 +363,8 @@ static int run_io_job(struct kcopyd_job *job)

if (job->rw == READ)
r = dm_io(&io_req, 1, &job->source, NULL);
- else {
- if (job->num_dests > 1)
- io_req.bi_rw |= REQ_UNPLUG;
+ else
r = dm_io(&io_req, job->num_dests, job->dests, NULL);
- }

return r;
}
diff --git a/drivers/md/md.c b/drivers/md/md.c
index ca0d79c..28f9c1e 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -777,8 +777,7 @@ void md_super_write(mddev_t *mddev, mdk_rdev_t *rdev,
bio->bi_end_io = super_written;

atomic_inc(&mddev->pending_writes);
- submit_bio(REQ_WRITE | REQ_SYNC | REQ_UNPLUG | REQ_FLUSH | REQ_FUA,
- bio);
+ submit_bio(REQ_WRITE | REQ_SYNC | REQ_FLUSH | REQ_FUA, bio);
}

void md_super_wait(mddev_t *mddev)
@@ -806,7 +805,7 @@ int sync_page_io(mdk_rdev_t *rdev, sector_t sector, int size,
struct completion event;
int ret;

- rw |= REQ_SYNC | REQ_UNPLUG;
+ rw |= REQ_SYNC;

bio->bi_bdev = (metadata_op && rdev->meta_bdev) ?
rdev->meta_bdev : rdev->bdev;
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 92ac519..b76f7cd 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -2182,7 +2182,7 @@ static int __extent_writepage(struct page *page, struct writeback_control *wbc,
unsigned long nr_written = 0;

if (wbc->sync_mode == WB_SYNC_ALL)
- write_flags = WRITE_SYNC_PLUG;
+ write_flags = WRITE_SYNC;
else
write_flags = WRITE;

diff --git a/fs/buffer.c b/fs/buffer.c
index f903f2e..19ae76a 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -767,7 +767,7 @@ static int fsync_buffers_list(spinlock_t *lock, struct list_head *list)
* still in flight on potentially older
* contents.
*/
- write_dirty_buffer(bh, WRITE_SYNC_PLUG);
+ write_dirty_buffer(bh, WRITE_SYNC);

/*
* Kick off IO for the previous mapping. Note
@@ -1602,14 +1602,11 @@ EXPORT_SYMBOL(unmap_underlying_metadata);
* prevents this contention from occurring.
*
* If block_write_full_page() is called with wbc->sync_mode ==
- * WB_SYNC_ALL, the writes are posted using WRITE_SYNC_PLUG; this
- * causes the writes to be flagged as synchronous writes, but the
- * block device queue will NOT be unplugged, since usually many pages
- * will be pushed to the out before the higher-level caller actually
- * waits for the writes to be completed. The various wait functions,
- * such as wait_on_writeback_range() will ultimately call sync_page()
- * which will ultimately call blk_run_backing_dev(), which will end up
- * unplugging the device queue.
+ * WB_SYNC_ALL, the writes are posted using WRITE_SYNC; this
+ * causes the writes to be flagged as synchronous writes.
+ * The various wait functions, such as wait_on_writeback_range() will
+ * ultimately call sync_page() which will ultimately call
+ * blk_run_backing_dev(), which will end up unplugging the device queue.
*/
static int __block_write_full_page(struct inode *inode, struct page *page,
get_block_t *get_block, struct writeback_control *wbc,
@@ -1622,7 +1619,7 @@ static int __block_write_full_page(struct inode *inode, struct page *page,
const unsigned blocksize = 1 << inode->i_blkbits;
int nr_underway = 0;
int write_op = (wbc->sync_mode == WB_SYNC_ALL ?
- WRITE_SYNC_PLUG : WRITE);
+ WRITE_SYNC : WRITE);

BUG_ON(!PageLocked(page));

diff --git a/fs/direct-io.c b/fs/direct-io.c
index df709b3..4260831 100644
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -1173,7 +1173,7 @@ __blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
struct dio *dio;

if (rw & WRITE)
- rw = WRITE_ODIRECT_PLUG;
+ rw = WRITE_ODIRECT;

if (bdev)
bdev_blkbits = blksize_bits(bdev_logical_block_size(bdev));
diff --git a/fs/ext4/page-io.c b/fs/ext4/page-io.c
index 955cc30..e2cd90e 100644
--- a/fs/ext4/page-io.c
+++ b/fs/ext4/page-io.c
@@ -310,8 +310,7 @@ static int io_submit_init(struct ext4_io_submit *io,
io_end->offset = (page->index << PAGE_CACHE_SHIFT) + bh_offset(bh);

io->io_bio = bio;
- io->io_op = (wbc->sync_mode == WB_SYNC_ALL ?
- WRITE_SYNC_PLUG : WRITE);
+ io->io_op = (wbc->sync_mode == WB_SYNC_ALL ? WRITE_SYNC : WRITE);
io->io_next_block = bh->b_blocknr;
return 0;
}
diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
index eb01f35..7f1c112 100644
--- a/fs/gfs2/log.c
+++ b/fs/gfs2/log.c
@@ -121,7 +121,7 @@ __acquires(&sdp->sd_log_lock)
lock_buffer(bh);
if (test_clear_buffer_dirty(bh)) {
bh->b_end_io = end_buffer_write_sync;
- submit_bh(WRITE_SYNC_PLUG, bh);
+ submit_bh(WRITE_SYNC, bh);
} else {
unlock_buffer(bh);
brelse(bh);
@@ -647,7 +647,7 @@ static void gfs2_ordered_write(struct gfs2_sbd *sdp)
lock_buffer(bh);
if (buffer_mapped(bh) && test_clear_buffer_dirty(bh)) {
bh->b_end_io = end_buffer_write_sync;
- submit_bh(WRITE_SYNC_PLUG, bh);
+ submit_bh(WRITE_SYNC, bh);
} else {
unlock_buffer(bh);
brelse(bh);
diff --git a/fs/gfs2/lops.c b/fs/gfs2/lops.c
index bf33f82..48b545a 100644
--- a/fs/gfs2/lops.c
+++ b/fs/gfs2/lops.c
@@ -200,7 +200,7 @@ static void buf_lo_before_commit(struct gfs2_sbd *sdp)
}

gfs2_log_unlock(sdp);
- submit_bh(WRITE_SYNC_PLUG, bh);
+ submit_bh(WRITE_SYNC, bh);
gfs2_log_lock(sdp);

n = 0;
@@ -210,7 +210,7 @@ static void buf_lo_before_commit(struct gfs2_sbd *sdp)
gfs2_log_unlock(sdp);
lock_buffer(bd2->bd_bh);
bh = gfs2_log_fake_buf(sdp, bd2->bd_bh);
- submit_bh(WRITE_SYNC_PLUG, bh);
+ submit_bh(WRITE_SYNC, bh);
gfs2_log_lock(sdp);
if (++n >= num)
break;
@@ -352,7 +352,7 @@ static void revoke_lo_before_commit(struct gfs2_sbd *sdp)
sdp->sd_log_num_revoke--;

if (offset + sizeof(u64) > sdp->sd_sb.sb_bsize) {
- submit_bh(WRITE_SYNC_PLUG, bh);
+ submit_bh(WRITE_SYNC, bh);

bh = gfs2_log_get_buf(sdp);
mh = (struct gfs2_meta_header *)bh->b_data;
@@ -369,7 +369,7 @@ static void revoke_lo_before_commit(struct gfs2_sbd *sdp)
}
gfs2_assert_withdraw(sdp, !sdp->sd_log_num_revoke);

- submit_bh(WRITE_SYNC_PLUG, bh);
+ submit_bh(WRITE_SYNC, bh);
}

static void revoke_lo_before_scan(struct gfs2_jdesc *jd,
@@ -571,7 +571,7 @@ static void gfs2_write_blocks(struct gfs2_sbd *sdp, struct buffer_head *bh,
ptr = bh_log_ptr(bh);

get_bh(bh);
- submit_bh(WRITE_SYNC_PLUG, bh);
+ submit_bh(WRITE_SYNC, bh);
gfs2_log_lock(sdp);
while(!list_empty(list)) {
bd = list_entry(list->next, struct gfs2_bufdata, bd_le.le_list);
@@ -597,7 +597,7 @@ static void gfs2_write_blocks(struct gfs2_sbd *sdp, struct buffer_head *bh,
} else {
bh1 = gfs2_log_fake_buf(sdp, bd->bd_bh);
}
- submit_bh(WRITE_SYNC_PLUG, bh1);
+ submit_bh(WRITE_SYNC, bh1);
gfs2_log_lock(sdp);
ptr += 2;
}
diff --git a/fs/gfs2/meta_io.c b/fs/gfs2/meta_io.c
index a566331..867b713 100644
--- a/fs/gfs2/meta_io.c
+++ b/fs/gfs2/meta_io.c
@@ -37,7 +37,7 @@ static int gfs2_aspace_writepage(struct page *page, struct writeback_control *wb
struct buffer_head *bh, *head;
int nr_underway = 0;
int write_op = REQ_META |
- (wbc->sync_mode == WB_SYNC_ALL ? WRITE_SYNC_PLUG : WRITE);
+ (wbc->sync_mode == WB_SYNC_ALL ? WRITE_SYNC : WRITE);

BUG_ON(!PageLocked(page));
BUG_ON(!page_has_buffers(page));
diff --git a/fs/jbd/commit.c b/fs/jbd/commit.c
index 34a4861..66be299 100644
--- a/fs/jbd/commit.c
+++ b/fs/jbd/commit.c
@@ -333,7 +333,7 @@ void journal_commit_transaction(journal_t *journal)
* instead we rely on sync_buffer() doing the unplug for us.
*/
if (commit_transaction->t_synchronous_commit)
- write_op = WRITE_SYNC_PLUG;
+ write_op = WRITE_SYNC;
spin_lock(&commit_transaction->t_handle_lock);
while (commit_transaction->t_updates) {
DEFINE_WAIT(wait);
diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c
index f3ad159..3da1cc4 100644
--- a/fs/jbd2/commit.c
+++ b/fs/jbd2/commit.c
@@ -137,9 +137,9 @@ static int journal_submit_commit_record(journal_t *journal,
if (journal->j_flags & JBD2_BARRIER &&
!JBD2_HAS_INCOMPAT_FEATURE(journal,
JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT))
- ret = submit_bh(WRITE_SYNC_PLUG | WRITE_FLUSH_FUA, bh);
+ ret = submit_bh(WRITE_SYNC | WRITE_FLUSH_FUA, bh);
else
- ret = submit_bh(WRITE_SYNC_PLUG, bh);
+ ret = submit_bh(WRITE_SYNC, bh);

*cbh = bh;
return ret;
@@ -369,7 +369,7 @@ void jbd2_journal_commit_transaction(journal_t *journal)
* instead we rely on sync_buffer() doing the unplug for us.
*/
if (commit_transaction->t_synchronous_commit)
- write_op = WRITE_SYNC_PLUG;
+ write_op = WRITE_SYNC;
trace_jbd2_commit_locking(journal, commit_transaction);
stats.run.rs_wait = commit_transaction->t_max_wait;
stats.run.rs_locked = jiffies;
diff --git a/fs/nilfs2/segbuf.c b/fs/nilfs2/segbuf.c
index 0f83e93..2853ff2 100644
--- a/fs/nilfs2/segbuf.c
+++ b/fs/nilfs2/segbuf.c
@@ -509,7 +509,7 @@ static int nilfs_segbuf_write(struct nilfs_segment_buffer *segbuf,
* Last BIO is always sent through the following
* submission.
*/
- rw |= REQ_SYNC | REQ_UNPLUG;
+ rw |= REQ_SYNC;
res = nilfs_segbuf_submit_bio(segbuf, &wi, rw);
}

diff --git a/fs/xfs/linux-2.6/xfs_aops.c b/fs/xfs/linux-2.6/xfs_aops.c
index 83c1c20..6bbb0ee 100644
--- a/fs/xfs/linux-2.6/xfs_aops.c
+++ b/fs/xfs/linux-2.6/xfs_aops.c
@@ -413,8 +413,7 @@ xfs_submit_ioend_bio(
if (xfs_ioend_new_eof(ioend))
xfs_mark_inode_dirty(XFS_I(ioend->io_inode));

- submit_bio(wbc->sync_mode == WB_SYNC_ALL ?
- WRITE_SYNC_PLUG : WRITE, bio);
+ submit_bio(wbc->sync_mode == WB_SYNC_ALL ? WRITE_SYNC : WRITE, bio);
}

STATIC struct bio *
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 16b2864..be50d9e 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -128,7 +128,6 @@ enum rq_flag_bits {
__REQ_NOIDLE, /* don't anticipate more IO after this one */

/* bio only flags */
- __REQ_UNPLUG, /* unplug the immediately after submission */
__REQ_RAHEAD, /* read ahead, can fail anytime */
__REQ_THROTTLED, /* This bio has already been subjected to
* throttling rules. Don't do it again. */
@@ -172,7 +171,6 @@ enum rq_flag_bits {
REQ_NOIDLE | REQ_FLUSH | REQ_FUA)
#define REQ_CLONE_MASK REQ_COMMON_MASK

-#define REQ_UNPLUG (1 << __REQ_UNPLUG)
#define REQ_RAHEAD (1 << __REQ_RAHEAD)
#define REQ_THROTTLED (1 << __REQ_THROTTLED)

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 9f2cf69..543e226 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -135,16 +135,10 @@ struct inodes_stat_t {
* block layer could (in theory) choose to ignore this
* request if it runs into resource problems.
* WRITE A normal async write. Device will be plugged.
- * WRITE_SYNC_PLUG Synchronous write. Identical to WRITE, but passes down
+ * WRITE_SYNC Synchronous write. Identical to WRITE, but passes down
* the hint that someone will be waiting on this IO
- * shortly. The device must still be unplugged explicitly,
- * WRITE_SYNC_PLUG does not do this as we could be
- * submitting more writes before we actually wait on any
- * of them.
- * WRITE_SYNC Like WRITE_SYNC_PLUG, but also unplugs the device
- * immediately after submission. The write equivalent
- * of READ_SYNC.
- * WRITE_ODIRECT_PLUG Special case write for O_DIRECT only.
+ * shortly. The write equivalent of READ_SYNC.
+ * WRITE_ODIRECT Special case write for O_DIRECT only.
* WRITE_FLUSH Like WRITE_SYNC but with preceding cache flush.
* WRITE_FUA Like WRITE_SYNC but data is guaranteed to be on
* non-volatile media on completion.
@@ -160,18 +154,14 @@ struct inodes_stat_t {
#define WRITE RW_MASK
#define READA RWA_MASK

-#define READ_SYNC (READ | REQ_SYNC | REQ_UNPLUG)
+#define READ_SYNC (READ | REQ_SYNC)
#define READ_META (READ | REQ_META)
-#define WRITE_SYNC_PLUG (WRITE | REQ_SYNC | REQ_NOIDLE)
-#define WRITE_SYNC (WRITE | REQ_SYNC | REQ_NOIDLE | REQ_UNPLUG)
-#define WRITE_ODIRECT_PLUG (WRITE | REQ_SYNC)
+#define WRITE_SYNC (WRITE | REQ_SYNC | REQ_NOIDLE)
+#define WRITE_ODIRECT (WRITE | REQ_SYNC)
#define WRITE_META (WRITE | REQ_META)
-#define WRITE_FLUSH (WRITE | REQ_SYNC | REQ_NOIDLE | REQ_UNPLUG | \
- REQ_FLUSH)
-#define WRITE_FUA (WRITE | REQ_SYNC | REQ_NOIDLE | REQ_UNPLUG | \
- REQ_FUA)
-#define WRITE_FLUSH_FUA (WRITE | REQ_SYNC | REQ_NOIDLE | REQ_UNPLUG | \
- REQ_FLUSH | REQ_FUA)
+#define WRITE_FLUSH (WRITE | REQ_SYNC | REQ_NOIDLE | REQ_FLUSH)
+#define WRITE_FUA (WRITE | REQ_SYNC | REQ_NOIDLE | REQ_FUA)
+#define WRITE_FLUSH_FUA (WRITE | REQ_SYNC | REQ_NOIDLE | REQ_FLUSH | REQ_FUA)

#define SEL_IN 1
#define SEL_OUT 2
diff --git a/kernel/power/block_io.c b/kernel/power/block_io.c
index 83bbc7c..d09dd10 100644
--- a/kernel/power/block_io.c
+++ b/kernel/power/block_io.c
@@ -28,7 +28,7 @@
static int submit(int rw, struct block_device *bdev, sector_t sector,
struct page *page, struct bio **bio_chain)
{
- const int bio_rw = rw | REQ_SYNC | REQ_UNPLUG;
+ const int bio_rw = rw | REQ_SYNC;
struct bio *bio;

bio = bio_alloc(__GFP_WAIT | __GFP_HIGH, 1);
diff --git a/mm/page_io.c b/mm/page_io.c
index 2dee975..dc76b4d 100644
--- a/mm/page_io.c
+++ b/mm/page_io.c
@@ -106,7 +106,7 @@ int swap_writepage(struct page *page, struct writeback_control *wbc)
goto out;
}
if (wbc->sync_mode == WB_SYNC_ALL)
- rw |= REQ_SYNC | REQ_UNPLUG;
+ rw |= REQ_SYNC;
count_vm_event(PSWPOUT);
set_page_writeback(page);
unlock_page(page);

--
Jens Axboe

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