Revert "f2fs: enhance multi-threads performance"

This reports performance regression by Yuanhan Liu.
The basic idea was to reduce one-point mutex, but it turns out this causes
another contention like context swithes.

https://lkml.org/lkml/2015/4/21/11

Until finishing the analysis on this issue, I'd like to revert this for a while.

This reverts commit 78373b7319abdf15050af5b1632c4c8b8b398f33.

3 files changed, 9 insertions, 0 deletions

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index b91b0e10678e..1e1aae669fa8 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -1513,6 +1513,7 @@ static int f2fs_write_data_pages(struct address_space *mapping,
 {
         struct inode *inode = mapping->host;
         struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
+        bool locked = false;
         int ret;
         long diff;
 
@@ -1533,7 +1534,13 @@ static int f2fs_write_data_pages(struct address_space *mapping,
 
         diff = nr_pages_to_write(sbi, DATA, wbc);
 
+        if (!S_ISDIR(inode->i_mode)) {
+                mutex_lock(&sbi->writepages);
+                locked = true;
+        }
         ret = write_cache_pages(mapping, wbc, __f2fs_writepage, mapping);
+        if (locked)
+                mutex_unlock(&sbi->writepages);
 
         f2fs_submit_merged_bio(sbi, DATA, WRITE);
 
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index d8921cf2ba9a..8de34ab6d5b1 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -625,6 +625,7 @@ struct f2fs_sb_info {
         struct mutex cp_mutex;                  /* checkpoint procedure lock */
         struct rw_semaphore cp_rwsem;           /* blocking FS operations */
         struct rw_semaphore node_write;         /* locking node writes */
+        struct mutex writepages;                /* mutex for writepages() */
         wait_queue_head_t cp_wait;
 
         struct inode_management im[MAX_INO_ENTRY];      /* manage inode cache */
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 160b88346b24..b2dd1b01f076 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -1035,6 +1035,7 @@ try_onemore:
         sbi->raw_super = raw_super;
         sbi->raw_super_buf = raw_super_buf;
         mutex_init(&sbi->gc_mutex);
+        mutex_init(&sbi->writepages);
         mutex_init(&sbi->cp_mutex);
         init_rwsem(&sbi->node_write);
         clear_sbi_flag(sbi, SBI_POR_DOING);