+ f2fs-change-retry-waiting-for-f2fs_write_single_data_page.patch added to -mm tree

+ f2fs-change-retry-waiting-for-f2fs_write_single_data_page.patch added to -mm tree

[akpm]

The patch titled
     Subject: f2fs: change retry waiting for f2fs_write_single_data_page()
has been added to the -mm tree.  Its filename is
     f2fs-change-retry-waiting-for-f2fs_write_single_data_page.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/f2fs-change-retry-waiting-for-f2fs_write_single_data_page.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/f2fs-change-retry-waiting-for-f2fs_write_single_data_page.patch

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------------------------------------------------------
From: NeilBrown <neilb@suse.de>
Subject: f2fs: change retry waiting for f2fs_write_single_data_page()

f2fs_write_single_data_page() can return -EAGAIN if it cannot get the
cp_rwsem lock - it holds a page lock and so cannot wait for it.

Some code which calls f2fs_write_single_data_page() use congestion_wait()
and then tries again.  congestion_wait() doesn't do anything useful as
congestion is no longer tracked.  So this is just a simple sleep.

A better approach is it wait until the cp_rwsem lock can be taken - then
try again.  There is certainly no point trying again *before* the lock can
be taken.

Link: https://lkml.kernel.org/r/164325158956.29787.7016948342209980097.stgit@noble.brown
Signed-off-by: NeilBrown <neilb@suse.de>
Cc: Anna Schumaker <Anna.Schumaker@Netapp.com>
Cc: Chao Yu <chao@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Darrick J. Wong <djwong@kernel.org>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Ilya Dryomov <idryomov@gmail.com>
Cc: Jaegeuk Kim <jaegeuk@kernel.org>
Cc: Jeff Layton <jlayton@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Lars Ellenberg <lars.ellenberg@linbit.com>
Cc: Miklos Szeredi <miklos@szeredi.hu>
Cc: Paolo Valente <paolo.valente@linaro.org>
Cc: Philipp Reisner <philipp.reisner@linbit.com>
Cc: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Cc: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 fs/f2fs/compress.c |    6 +++---
 fs/f2fs/data.c     |    9 ++++++---
 2 files changed, 9 insertions(+), 6 deletions(-)

--- a/fs/f2fs/compress.c~f2fs-change-retry-waiting-for-f2fs_write_single_data_page
+++ a/fs/f2fs/compress.c
@@ -1505,9 +1505,9 @@ continue_unlock:
 				if (IS_NOQUOTA(cc->inode))
 					return 0;
 				ret = 0;
-				cond_resched();
-				congestion_wait(BLK_RW_ASYNC,
-						DEFAULT_IO_TIMEOUT);
+				/* Wait until we can get the lock, then try again. */
+				f2fs_lock_op(F2FS_I_SB(cc->inode));
+				f2fs_unlock_op(F2FS_I_SB(cc->inode));
 				goto retry_write;
 			}
 			return ret;
--- a/fs/f2fs/data.c~f2fs-change-retry-waiting-for-f2fs_write_single_data_page
+++ a/fs/f2fs/data.c
@@ -3047,9 +3047,12 @@ result:
 				} else if (ret == -EAGAIN) {
 					ret = 0;
 					if (wbc->sync_mode == WB_SYNC_ALL) {
-						cond_resched();
-						congestion_wait(BLK_RW_ASYNC,
-							DEFAULT_IO_TIMEOUT);
+						/* Wait until we can get the
+						 * lock, then try again.
+						 */
+						f2fs_lock_op(F2FS_I_SB(mapping->host));
+						f2fs_unlock_op(F2FS_I_SB(mapping->host));
+
 						goto retry_write;
 					}
 					goto next;
_

Patches currently in -mm which might be from neilb@suse.de are

remove-inode_congested.patch
remove-bdi_congested-and-wb_congested-and-related-functions.patch
f2fs-change-retry-waiting-for-f2fs_write_single_data_page.patch
f2f2-replace-some-congestion_wait-calls-with-io_schedule_timeout.patch
cephfs-dont-set-clear-bdi_congestion.patch
fuse-dont-set-clear-bdi_congested.patch
nfs-remove-congestion-control.patch
block-bfq-ioschedc-use-false-rather-than-blk_rw_async.patch
remove-congestion-tracking-framework.patch
mm-discard-__gfp_atomic.patch