kill-the-bkl/reiserfs: factorize the locking in reiserfs_write_end()

reiserfs_write_end() is a hot path in reiserfs.
We have two wasteful write lock lock/release inside that can be gathered
without changing the code logic.

This patch factorizes them out in a single protected section, reducing the
number of contentions inside.

[ Impact: reduce lock contention in a reiserfs hotpath ]

Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

1 files changed, 15 insertions, 10 deletions

diff --git a/fs/reiserfs/inode.c b/fs/reiserfs/inode.c
index 6114050f342e..853f4f6fe920 100644
--- a/fs/reiserfs/inode.c
+++ b/fs/reiserfs/inode.c
@@ -2681,6 +2681,8 @@ static int reiserfs_write_end(struct file *file, struct address_space *mapping,
         int update_sd = 0;
         struct reiserfs_transaction_handle *th;
         unsigned start;
+        int lock_depth = 0;
+        bool locked = false;
 
         if ((unsigned long)fsdata & AOP_FLAG_CONT_EXPAND)
                 pos ++;
@@ -2707,9 +2709,11 @@ static int reiserfs_write_end(struct file *file, struct address_space *mapping,
          ** to do the i_size updates here.
          */
         pos += copied;
+
         if (pos > inode->i_size) {
                 struct reiserfs_transaction_handle myth;
-                reiserfs_write_lock(inode->i_sb);
+                lock_depth = reiserfs_write_lock_once(inode->i_sb);
+                locked = true;
                 /* If the file have grown beyond the border where it
                    can have a tail, unmark it as needing a tail
                    packing */
@@ -2720,10 +2724,9 @@ static int reiserfs_write_end(struct file *file, struct address_space *mapping,
                         REISERFS_I(inode)->i_flags &= ~i_pack_on_close_mask;
 
                 ret = journal_begin(&myth, inode->i_sb, 1);
-                if (ret) {
-                        reiserfs_write_unlock(inode->i_sb);
+                if (ret)
                         goto journal_error;
-                }
+
                 reiserfs_update_inode_transaction(inode);
                 inode->i_size = pos;
                 /*
@@ -2735,34 +2738,36 @@ static int reiserfs_write_end(struct file *file, struct address_space *mapping,
                 reiserfs_update_sd(&myth, inode);
                 update_sd = 1;
                 ret = journal_end(&myth, inode->i_sb, 1);
-                reiserfs_write_unlock(inode->i_sb);
                 if (ret)
                         goto journal_error;
         }
         if (th) {
-                reiserfs_write_lock(inode->i_sb);
+                if (!locked) {
+                        lock_depth = reiserfs_write_lock_once(inode->i_sb);
+                        locked = true;
+                }
                 if (!update_sd)
                         mark_inode_dirty(inode);
                 ret = reiserfs_end_persistent_transaction(th);
-                reiserfs_write_unlock(inode->i_sb);
                 if (ret)
                         goto out;
         }
 
       out:
+        if (locked)
+                reiserfs_write_unlock_once(inode->i_sb, lock_depth);
         unlock_page(page);
         page_cache_release(page);
         return ret == 0 ? copied : ret;
 
       journal_error:
+        reiserfs_write_unlock_once(inode->i_sb, lock_depth);
+        locked = false;
         if (th) {
-                reiserfs_write_lock(inode->i_sb);
                 if (!update_sd)
                         reiserfs_update_sd(th, inode);
                 ret = reiserfs_end_persistent_transaction(th);
-                reiserfs_write_unlock(inode->i_sb);
         }
-
         goto out;
 }