[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/fs-writeback.c b/fs/fs-writeback.c
index 6db95cf3aaa2..031b27a4bc9a 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -623,7 +623,6 @@ int generic_osync_inode(struct inode *inode, struct address_space *mapping, int
         int need_write_inode_now = 0;
         int err2;
 
-        current->flags |= PF_SYNCWRITE;
         if (what & OSYNC_DATA)
                 err = filemap_fdatawrite(mapping);
         if (what & (OSYNC_METADATA|OSYNC_DATA)) {
@@ -636,7 +635,6 @@ int generic_osync_inode(struct inode *inode, struct address_space *mapping, int
                 if (!err)
                         err = err2;
         }
-        current->flags &= ~PF_SYNCWRITE;
 
         spin_lock(&inode_lock);
         if ((inode->i_state & I_DIRTY) &&