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SubjectRe: [f2fs-dev] [PATCH v3] f2fs: fix performance issue observed with multi-thread sequential read
This reverts the commit - "b93f771 - f2fs: remove writepages lock"
to fix the drop in sequential read throughput.

Test: ./tiotest -t 32 -d /data/tio_tmp -f 32 -b 524288 -k 1 -k 3 -L
device: UFS

Before -
read throughput: 185 MB/s
total read requests: 85177 (of these ~80000 are 4KB size requests).
total write requests: 2546 (of these ~2208 requests are written in 512KB).

After -
read throughput: 758 MB/s
total read requests: 2417 (of these ~2042 are 512KB reads).
total write requests: 2701 (of these ~2034 requests are written in 512KB).

Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
---
Changelog from v2:
- fix deadlock in f2fs_gc

fs/f2fs/data.c | 9 +++++++++
fs/f2fs/f2fs.h | 1 +
fs/f2fs/super.c | 1 +
3 files changed, 11 insertions(+)

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 45f043ee48bd..9f0149cdeed8 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -2132,6 +2132,7 @@ static int __f2fs_write_data_pages(struct address_space *mapping,
struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
struct blk_plug plug;
int ret;
+ bool locked = false;

/* deal with chardevs and other special file */
if (!mapping->a_ops->writepage)
@@ -2162,10 +2163,18 @@ static int __f2fs_write_data_pages(struct address_space *mapping,
else if (atomic_read(&sbi->wb_sync_req[DATA]))
goto skip_write;

+ if (!S_ISDIR(inode->i_mode)) {
+ mutex_lock(&sbi->writepages);
+ locked = true;
+ }
+
blk_start_plug(&plug);
ret = f2fs_write_cache_pages(mapping, wbc, io_type);
blk_finish_plug(&plug);

+ if (locked)
+ mutex_unlock(&sbi->writepages);
+
if (wbc->sync_mode == WB_SYNC_ALL)
atomic_dec(&sbi->wb_sync_req[DATA]);
/*
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index b1c127d8383b..29bbc55cbc0b 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -1133,6 +1133,7 @@ struct f2fs_sb_info {
struct rw_semaphore sb_lock; /* lock for raw super block */
int valid_super_block; /* valid super block no */
unsigned long s_flag; /* flags for sbi */
+ struct mutex writepages; /* mutex for writepages() */

#ifdef CONFIG_BLK_DEV_ZONED
unsigned int blocks_per_blkz; /* F2FS blocks per zone */
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index be41dbd7b261..53d70b64fea1 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -2842,6 +2842,7 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
/* init f2fs-specific super block info */
sbi->valid_super_block = valid_super_block;
mutex_init(&sbi->gc_mutex);
+ mutex_init(&sbi->writepages);
mutex_init(&sbi->cp_mutex);
init_rwsem(&sbi->node_write);
init_rwsem(&sbi->node_change);
--
2.17.0.441.gb46fe60e1d-goog
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