writeback: remove nonblocking/encountered_congestion references
Wu Fengguang [Tue, 26 Oct 2010 21:21:26 +0000 (14:21 -0700)]
This removes more dead code that was somehow missed by commit 0d99519efef
(writeback: remove unused nonblocking and congestion checks).  There are
no behavior change except for the removal of two entries from one of the
ext4 tracing interface.

The nonblocking checks in ->writepages are no longer used because the
flusher now prefer to block on get_request_wait() than to skip inodes on
IO congestion.  The latter will lead to more seeky IO.

The nonblocking checks in ->writepage are no longer used because it's
redundant with the WB_SYNC_NONE check.

We no long set ->nonblocking in VM page out and page migration, because
a) it's effectively redundant with WB_SYNC_NONE in current code
b) it's old semantic of "Don't get stuck on request queues" is mis-behavior:
   that would skip some dirty inodes on congestion and page out others, which
   is unfair in terms of LRU age.

Inspired by Christoph Hellwig. Thanks!

Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: David Howells <dhowells@redhat.com>
Cc: Sage Weil <sage@newdream.net>
Cc: Steve French <sfrench@samba.org>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

12 files changed:
fs/afs/write.c
fs/buffer.c
fs/ceph/addr.c
fs/cifs/file.c
fs/gfs2/meta_io.c
fs/nfs/write.c
fs/reiserfs/inode.c
fs/xfs/linux-2.6/xfs_aops.c
include/trace/events/ext4.h
include/trace/events/writeback.h
mm/migrate.c
mm/vmscan.c

index 722743b..15690bb 100644 (file)
@@ -438,7 +438,6 @@ no_more:
  */
 int afs_writepage(struct page *page, struct writeback_control *wbc)
 {
-       struct backing_dev_info *bdi = page->mapping->backing_dev_info;
        struct afs_writeback *wb;
        int ret;
 
@@ -455,8 +454,6 @@ int afs_writepage(struct page *page, struct writeback_control *wbc)
        }
 
        wbc->nr_to_write -= ret;
-       if (wbc->nonblocking && bdi_write_congested(bdi))
-               wbc->encountered_congestion = 1;
 
        _leave(" = 0");
        return 0;
@@ -469,7 +466,6 @@ static int afs_writepages_region(struct address_space *mapping,
                                 struct writeback_control *wbc,
                                 pgoff_t index, pgoff_t end, pgoff_t *_next)
 {
-       struct backing_dev_info *bdi = mapping->backing_dev_info;
        struct afs_writeback *wb;
        struct page *page;
        int ret, n;
@@ -529,11 +525,6 @@ static int afs_writepages_region(struct address_space *mapping,
 
                wbc->nr_to_write -= ret;
 
-               if (wbc->nonblocking && bdi_write_congested(bdi)) {
-                       wbc->encountered_congestion = 1;
-                       break;
-               }
-
                cond_resched();
        } while (index < end && wbc->nr_to_write > 0);
 
@@ -548,24 +539,16 @@ static int afs_writepages_region(struct address_space *mapping,
 int afs_writepages(struct address_space *mapping,
                   struct writeback_control *wbc)
 {
-       struct backing_dev_info *bdi = mapping->backing_dev_info;
        pgoff_t start, end, next;
        int ret;
 
        _enter("");
 
-       if (wbc->nonblocking && bdi_write_congested(bdi)) {
-               wbc->encountered_congestion = 1;
-               _leave(" = 0 [congest]");
-               return 0;
-       }
-
        if (wbc->range_cyclic) {
                start = mapping->writeback_index;
                end = -1;
                ret = afs_writepages_region(mapping, wbc, start, end, &next);
-               if (start > 0 && wbc->nr_to_write > 0 && ret == 0 &&
-                   !(wbc->nonblocking && wbc->encountered_congestion))
+               if (start > 0 && wbc->nr_to_write > 0 && ret == 0)
                        ret = afs_writepages_region(mapping, wbc, 0, start,
                                                    &next);
                mapping->writeback_index = next;
index 7f0b9b0..ec21a92 100644 (file)
@@ -1706,7 +1706,7 @@ static int __block_write_full_page(struct inode *inode, struct page *page,
                 * and kswapd activity, but those code paths have their own
                 * higher-level throttling.
                 */
-               if (wbc->sync_mode != WB_SYNC_NONE || !wbc->nonblocking) {
+               if (wbc->sync_mode != WB_SYNC_NONE) {
                        lock_buffer(bh);
                } else if (!trylock_buffer(bh)) {
                        redirty_page_for_writepage(wbc, page);
index 51bcc5c..e9c874a 100644 (file)
@@ -591,7 +591,6 @@ static int ceph_writepages_start(struct address_space *mapping,
                                 struct writeback_control *wbc)
 {
        struct inode *inode = mapping->host;
-       struct backing_dev_info *bdi = mapping->backing_dev_info;
        struct ceph_inode_info *ci = ceph_inode(inode);
        struct ceph_fs_client *fsc;
        pgoff_t index, start, end;
@@ -633,13 +632,6 @@ static int ceph_writepages_start(struct address_space *mapping,
 
        pagevec_init(&pvec, 0);
 
-       /* ?? */
-       if (wbc->nonblocking && bdi_write_congested(bdi)) {
-               dout(" writepages congested\n");
-               wbc->encountered_congestion = 1;
-               goto out_final;
-       }
-
        /* where to start/end? */
        if (wbc->range_cyclic) {
                start = mapping->writeback_index; /* Start from prev offset */
@@ -885,7 +877,6 @@ out:
                rc = 0;  /* vfs expects us to return 0 */
        ceph_put_snap_context(snapc);
        dout("writepages done, rc = %d\n", rc);
-out_final:
        return rc;
 }
 
index 8c81e7b..45af003 100644 (file)
@@ -1303,7 +1303,6 @@ static int cifs_partialpagewrite(struct page *page, unsigned from, unsigned to)
 static int cifs_writepages(struct address_space *mapping,
                           struct writeback_control *wbc)
 {
-       struct backing_dev_info *bdi = mapping->backing_dev_info;
        unsigned int bytes_to_write;
        unsigned int bytes_written;
        struct cifs_sb_info *cifs_sb;
@@ -1326,15 +1325,6 @@ static int cifs_writepages(struct address_space *mapping,
        int scanned = 0;
        int xid, long_op;
 
-       /*
-        * BB: Is this meaningful for a non-block-device file system?
-        * If it is, we should test it again after we do I/O
-        */
-       if (wbc->nonblocking && bdi_write_congested(bdi)) {
-               wbc->encountered_congestion = 1;
-               return 0;
-       }
-
        cifs_sb = CIFS_SB(mapping->host->i_sb);
 
        /*
index f3b071f..939739c 100644 (file)
@@ -55,7 +55,7 @@ static int gfs2_aspace_writepage(struct page *page, struct writeback_control *wb
                 * activity, but those code paths have their own higher-level
                 * throttling.
                 */
-               if (wbc->sync_mode != WB_SYNC_NONE || !wbc->nonblocking) {
+               if (wbc->sync_mode != WB_SYNC_NONE) {
                        lock_buffer(bh);
                } else if (!trylock_buffer(bh)) {
                        redirty_page_for_writepage(wbc, page);
index 605e292..4c14c17 100644 (file)
@@ -290,9 +290,7 @@ static int nfs_do_writepage(struct page *page, struct writeback_control *wbc, st
        nfs_add_stats(inode, NFSIOS_WRITEPAGES, 1);
 
        nfs_pageio_cond_complete(pgio, page->index);
-       ret = nfs_page_async_flush(pgio, page,
-                       wbc->sync_mode == WB_SYNC_NONE ||
-                       wbc->nonblocking != 0);
+       ret = nfs_page_async_flush(pgio, page, wbc->sync_mode == WB_SYNC_NONE);
        if (ret == -EAGAIN) {
                redirty_page_for_writepage(wbc, page);
                ret = 0;
index caa7583..c1f9389 100644 (file)
@@ -2438,7 +2438,7 @@ static int reiserfs_write_full_page(struct page *page,
                /* from this point on, we know the buffer is mapped to a
                 * real block and not a direct item
                 */
-               if (wbc->sync_mode != WB_SYNC_NONE || !wbc->nonblocking) {
+               if (wbc->sync_mode != WB_SYNC_NONE) {
                        lock_buffer(bh);
                } else {
                        if (!trylock_buffer(bh)) {
index b552f81..c9af48f 100644 (file)
@@ -1139,8 +1139,7 @@ xfs_vm_writepage(
                                type = IO_DELAY;
                                flags = BMAPI_ALLOCATE;
 
-                               if (wbc->sync_mode == WB_SYNC_NONE &&
-                                   wbc->nonblocking)
+                               if (wbc->sync_mode == WB_SYNC_NONE)
                                        flags |= BMAPI_TRYLOCK;
                        }
 
index 01e9e00..6bcb006 100644 (file)
@@ -242,18 +242,20 @@ TRACE_EVENT(ext4_da_writepages,
                __entry->pages_skipped  = wbc->pages_skipped;
                __entry->range_start    = wbc->range_start;
                __entry->range_end      = wbc->range_end;
-               __entry->nonblocking    = wbc->nonblocking;
                __entry->for_kupdate    = wbc->for_kupdate;
                __entry->for_reclaim    = wbc->for_reclaim;
                __entry->range_cyclic   = wbc->range_cyclic;
                __entry->writeback_index = inode->i_mapping->writeback_index;
        ),
 
-       TP_printk("dev %s ino %lu nr_to_write %ld pages_skipped %ld range_start %llu range_end %llu nonblocking %d for_kupdate %d for_reclaim %d range_cyclic %d writeback_index %lu",
+       TP_printk("dev %s ino %lu nr_to_write %ld pages_skipped %ld "
+                 "range_start %llu range_end %llu "
+                 "for_kupdate %d for_reclaim %d "
+                 "range_cyclic %d writeback_index %lu",
                  jbd2_dev_to_name(__entry->dev),
                  (unsigned long) __entry->ino, __entry->nr_to_write,
                  __entry->pages_skipped, __entry->range_start,
-                 __entry->range_end, __entry->nonblocking,
+                 __entry->range_end,
                  __entry->for_kupdate, __entry->for_reclaim,
                  __entry->range_cyclic,
                  (unsigned long) __entry->writeback_index)
index f345f66..0bb01ab 100644 (file)
@@ -96,8 +96,6 @@ DECLARE_EVENT_CLASS(wbc_class,
                __field(long, nr_to_write)
                __field(long, pages_skipped)
                __field(int, sync_mode)
-               __field(int, nonblocking)
-               __field(int, encountered_congestion)
                __field(int, for_kupdate)
                __field(int, for_background)
                __field(int, for_reclaim)
index f8c9bcc..d917ac3 100644 (file)
@@ -497,7 +497,6 @@ static int writeout(struct address_space *mapping, struct page *page)
                .nr_to_write = 1,
                .range_start = 0,
                .range_end = LLONG_MAX,
-               .nonblocking = 1,
                .for_reclaim = 1
        };
        int rc;
index b94c946..6cbc1aa 100644 (file)
@@ -376,7 +376,6 @@ static pageout_t pageout(struct page *page, struct address_space *mapping,
                        .nr_to_write = SWAP_CLUSTER_MAX,
                        .range_start = 0,
                        .range_end = LLONG_MAX,
-                       .nonblocking = 1,
                        .for_reclaim = 1,
                };