f2fs: avoid to use slab memory in f2fs_issue_flush for efficiency

If we use slab memory in f2fs_issue_flush(), we will face memory pressure and
latency time caused by racing of kmem_cache_{alloc,free}.

Let's alloc memory in stack instead of slab.

Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>

1 files changed, 9 insertions, 19 deletions

diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 2ecbffb91f37..f25f0e07e26f 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -25,7 +25,6 @@
 #define __reverse_ffz(x) __reverse_ffs(~(x))
 
 static struct kmem_cache *discard_entry_slab;
-static struct kmem_cache *flush_cmd_slab;
 
 /*
  * __reverse_ffs is copied from include/asm-generic/bitops/__ffs.h since
@@ -238,30 +237,28 @@ repeat:
 int f2fs_issue_flush(struct f2fs_sb_info *sbi)
 {
         struct flush_cmd_control *fcc = SM_I(sbi)->cmd_control_info;
-        struct flush_cmd *cmd;
-        int ret;
+        struct flush_cmd cmd;
 
         if (!test_opt(sbi, FLUSH_MERGE))
                 return blkdev_issue_flush(sbi->sb->s_bdev, GFP_KERNEL, NULL);
 
-        cmd = f2fs_kmem_cache_alloc(flush_cmd_slab, GFP_ATOMIC | __GFP_ZERO);
-        init_completion(&cmd->wait);
+        init_completion(&cmd.wait);
+        cmd.next = NULL;
 
         spin_lock(&fcc->issue_lock);
         if (fcc->issue_list)
-                fcc->issue_tail->next = cmd;
+                fcc->issue_tail->next = &cmd;
         else
-                fcc->issue_list = cmd;
-        fcc->issue_tail = cmd;
+                fcc->issue_list = &cmd;
+        fcc->issue_tail = &cmd;
         spin_unlock(&fcc->issue_lock);
 
         if (!fcc->dispatch_list)
                 wake_up(&fcc->flush_wait_queue);
 
-        wait_for_completion(&cmd->wait);
-        ret = cmd->ret;
-        kmem_cache_free(flush_cmd_slab, cmd);
-        return ret;
+        wait_for_completion(&cmd.wait);
+
+        return cmd.ret;
 }
 
 int create_flush_cmd_control(struct f2fs_sb_info *sbi)
@@ -2036,17 +2033,10 @@ int __init create_segment_manager_caches(void)
                         sizeof(struct discard_entry));
         if (!discard_entry_slab)
                 return -ENOMEM;
-        flush_cmd_slab = f2fs_kmem_cache_create("flush_command",
-                        sizeof(struct flush_cmd));
-        if (!flush_cmd_slab) {
-                kmem_cache_destroy(discard_entry_slab);
-                return -ENOMEM;
-        }
         return 0;
 }
 
 void destroy_segment_manager_caches(void)
 {
         kmem_cache_destroy(discard_entry_slab);
-        kmem_cache_destroy(flush_cmd_slab);
 }