[PATCH] fs: annotate refault stalls from bdev_read_page

[Minchan Kim]

From: Minchan Kim <minc...@google.com>

If block device supports rw_page operation, it doesn't submit bio
so 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.

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

Cc: Johannes Weiner <han...@cmpxchg.org>
Signed-off-by: Minchan Kim <minc...@google.com>
---
 fs/block_dev.c | 13 +++++++++++++
 mm/memory.c    |  1 +
 2 files changed, 14 insertions(+)

diff --git a/fs/block_dev.c b/fs/block_dev.c
index 9c073dbdc1b0..82ca28eb9a57 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -26,6 +26,7 @@
 #include <linux/writeback.h>
 #include <linux/mpage.h>
 #include <linux/mount.h>
+#include <linux/psi.h>
 #include <linux/pseudo_fs.h>
 #include <linux/uio.h>
 #include <linux/namei.h>
@@ -701,6 +702,8 @@ int bdev_read_page(struct block_device *bdev, sector_t 
sector,
 {
        const struct block_device_operations *ops = bdev->bd_disk->fops;
        int result = -EOPNOTSUPP;
+       unsigned long pflags;
+       bool workingset_read;
 
        if (!ops->rw_page || bdev_get_integrity(bdev))
                return result;
@@ -708,9 +711,19 @@ int bdev_read_page(struct block_device *bdev, sector_t 
sector,
        result = blk_queue_enter(bdev->bd_queue, 0);
        if (result)
                return result;
+
+       workingset_read = PageWorkingset(page);
+       if (workingset_read)
+               psi_memstall_enter(&pflags);
+
        result = ops->rw_page(bdev, sector + get_start_sect(bdev), page,
                              REQ_OP_READ);
+
+       if (workingset_read)
+               psi_memstall_leave(&pflags);
+
        blk_queue_exit(bdev->bd_queue);
+
        return result;
 }
 EXPORT_SYMBOL_GPL(bdev_read_page);
diff --git a/mm/memory.c b/mm/memory.c
index 06935826d71e..6357d5a0a2a5 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2801,6 +2801,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
                        if (page) {
                                __SetPageLocked(page);
                                __SetPageSwapBacked(page);
+                               SetPageWorkingset(page);
                                set_page_private(page, entry.val);
                                lru_cache_add_anon(page);
                                swap_readpage(page, true);
-- 
2.23.0.581.g78d2f28ef7-goog