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Commit 5b18331d authored by Minchan Kim's avatar Minchan Kim Committed by Suren Baghdasaryan
Browse files

UPSTREAM: mm/page_io.c: annotate refault stalls from swap_readpage 

If a block device supports rw_page operation, it doesn't submit bios so
the annotation in submit_bio() for refault stall doesn't work.  It
happens with zram in android, especially swap read path which could
consume CPU cycle for decompress.  It is also a problem for zswap which
uses frontswap.

Annotate swap_readpage() to account the synchronous IO overhead to
prevent underreport memory pressure.

[akpm@linux-foundation.org: add comment, per Johannes]
Link: http://lkml.kernel.org/r/20191010152134.38545-1-minchan@kernel.org


Signed-off-by: default avatarMinchan Kim <minchan@google.com>
Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Reviewed-by: default avatarShakeel Butt <shakeelb@google.com>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>

(cherry picked from commit 937790699be9c8100e5358625e7dfa8b32bd33f2)
Bug: 142418748
Signed-off-by: default avatarSuren Baghdasaryan <surenb@google.com>
Change-Id: Ibb3ca48ad331af38a99ea428dcfbd78a26758739
parent 4dcb4075

mm/page_io.c

+13 −2
Original line number Diff line number Diff line
@@ -22,6 +22,7 @@ 
#include <linux/writeback.h>

#include <linux/frontswap.h>

#include <linux/blkdev.h>

#include <linux/psi.h>

#include <linux/uio.h>

#include <linux/sched/task.h>

#include <asm/pgtable.h>
@@ -356,10 +357,19 @@ int swap_readpage(struct page *page, bool synchronous) 
	struct swap_info_struct *sis = page_swap_info(page);

	blk_qc_t qc;

	struct gendisk *disk;

	unsigned long pflags;



	VM_BUG_ON_PAGE(!PageSwapCache(page) && !synchronous, page);

	VM_BUG_ON_PAGE(!PageLocked(page), page);

	VM_BUG_ON_PAGE(PageUptodate(page), page);



	/*

	 * Count submission time as memory stall. When the device is congested,

	 * or the submitting cgroup IO-throttled, submission can be a

	 * significant part of overall IO time.

	 */

	psi_memstall_enter(&pflags);



	if (frontswap_load(page) == 0) {

		SetPageUptodate(page);

		unlock_page(page);
@@ -373,7 +383,7 @@ int swap_readpage(struct page *page, bool synchronous) 
		ret = mapping->a_ops->readpage(swap_file, page);

		if (!ret)

			count_vm_event(PSWPIN);

		return ret;

		goto out;

	}



	ret = bdev_read_page(sis->bdev, swap_page_sector(page), page);
@@ -384,7 +394,7 @@ int swap_readpage(struct page *page, bool synchronous) 
		}



		count_vm_event(PSWPIN);

		return 0;

		goto out;

	}



	ret = 0;
@@ -417,6 +427,7 @@ int swap_readpage(struct page *page, bool synchronous) 
	bio_put(bio);



out:

	psi_memstall_leave(&pflags);

	return ret;

}