nfs: remove congestion_end()

These patches aim to improve balance_dirty_pages() and directly address three
issues:
  1) inter device starvation
  2) stacked device deadlocks
  3) inter process starvation

1 and 2 are a direct result from removing the global dirty limit and using
per device dirty limits. By giving each device its own dirty limit is will
no longer starve another device, and the cyclic dependancy on the dirty limit
is broken.

In order to efficiently distribute the dirty limit across the independant
devices a floating proportion is used, this will allocate a share of the total
limit proportional to the device's recent activity.

3 is done by also scaling the dirty limit proportional to the current task's
recent dirty rate.

This patch:

nfs: remove congestion_end().  It's redundant, clear_bdi_congested() already
wakes the waiters.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
Cc: "J. Bruce Fields" <bfields@fieldses.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index e2bb66c34406d7cc6dc61b0557e0017166575dc8..82d7ee98c675da31aec4161512711f2ec5b9e5b3 100644 (file)
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -242,10 +242,8 @@ static void nfs_end_page_writeback(struct page *page)
        struct nfs_server *nfss = NFS_SERVER(inode);
 
        end_page_writeback(page);
-       if (atomic_long_dec_return(&nfss->writeback) < NFS_CONGESTION_OFF_THRESH) {
+       if (atomic_long_dec_return(&nfss->writeback) < NFS_CONGESTION_OFF_THRESH)
                clear_bdi_congested(&nfss->backing_dev_info, WRITE);
-               congestion_end(WRITE);
-       }
 }
 
 /*

diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index 7011d6255593dda940f859ab02e89e505d1a57ae..210933c336f54300ed69ab02a99d027fb83664f7 100644 (file)
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -93,7 +93,6 @@ static inline int bdi_rw_congested(struct backing_dev_info *bdi)
 void clear_bdi_congested(struct backing_dev_info *bdi, int rw);
 void set_bdi_congested(struct backing_dev_info *bdi, int rw);
 long congestion_wait(int rw, long timeout);
-void congestion_end(int rw);
 
 #define bdi_cap_writeback_dirty(bdi) \
        (!((bdi)->capabilities & BDI_CAP_NO_WRITEBACK))

diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index f50a2811f9dc86b876d24e75333558583c075f1d..841901a955955a8be07b88a5e75658743c0af5ef 100644 (file)
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -54,16 +54,3 @@ long congestion_wait(int rw, long timeout)
        return ret;
 }
 EXPORT_SYMBOL(congestion_wait);
-
-/**
- * congestion_end - wake up sleepers on a congested backing_dev_info
- * @rw: READ or WRITE
- */
-void congestion_end(int rw)
-{
-       wait_queue_head_t *wqh = &congestion_wqh[rw];
-
-       if (waitqueue_active(wqh))
-               wake_up(wqh);
-}
-EXPORT_SYMBOL(congestion_end);