[PATCH] Kill PF_SYNCWRITE flag

A process flag to indicate whether we are doing sync io is incredibly
ugly. It also causes performance problems when one does a lot of async
io and then proceeds to sync it. Part of the io will go out as async,
and the other part as sync. This causes a disconnect between the
previously submitted io and the synced io. For io schedulers such as CFQ,
this will cause us lost merges and suboptimal behaviour in scheduling.

Remove PF_SYNCWRITE completely from the fsync/msync paths, and let
the O_DIRECT path just directly indicate that the writes are sync
by using WRITE_SYNC instead.

Signed-off-by: Jens Axboe <axboe@suse.de>

1 files changed, 0 insertions, 2 deletions

diff --git a/fs/buffer.c b/fs/buffer.c
index 23f1f3a68077..373bb6292bdc 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -331,7 +331,6 @@ long do_fsync(struct file *file, int datasync)
                 goto out;
         }
 
-        current->flags |= PF_SYNCWRITE;
         ret = filemap_fdatawrite(mapping);
 
         /*
@@ -346,7 +345,6 @@ long do_fsync(struct file *file, int datasync)
         err = filemap_fdatawait(mapping);
         if (!ret)
                 ret = err;
-        current->flags &= ~PF_SYNCWRITE;
 out:
         return ret;
 }