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Date: Mon, 18 Jul 2011 17:34:09 +1000
From: Stephen Rothwell <sfr@...b.auug.org.au>
To: Wu Fengguang <fengguang.wu@...el.com>
Cc: linux-next@...r.kernel.org, linux-kernel@...r.kernel.org,
Dave Chinner <dchinner@...hat.com>,
Christoph Hellwig <hch@...radead.org>,
Al Viro <viro@...IV.linux.org.uk>
Subject: linux-next: manual merge of the writeback tree with the vfs tree
Hi Wu,
Today's linux-next merge of the writeback tree got a conflict in
fs/fs-writeback.c between commit dffe5a6c5214 ("superblock: move
pin_sb_for_writeback() to fs/super.c") from the vfs tree and commits
f758eeabeb96 ("writeback: split inode_wb_list_lock into
bdi_writeback.list_lock") and d46db3d58233 ("writeback: make
writeback_control.nr_to_write straight") from the writeback tree.
I fixed it up (I think - see below) and can carry the fix as necessary.
--
Cheers,
Stephen Rothwell sfr@...b.auug.org.au
diff --cc fs/fs-writeback.c
index b8c507c,6d49439..0000000
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@@ -460,6 -480,63 +480,37 @@@ writeback_single_inode(struct inode *in
return ret;
}
-/*
- * For background writeback the caller does not have the sb pinned
- * before calling writeback. So make sure that we do pin it, so it doesn't
- * go away while we are writing inodes from it.
- */
-static bool pin_sb_for_writeback(struct super_block *sb)
-{
- spin_lock(&sb_lock);
- if (list_empty(&sb->s_instances)) {
- spin_unlock(&sb_lock);
- return false;
- }
-
- sb->s_count++;
- spin_unlock(&sb_lock);
-
- if (down_read_trylock(&sb->s_umount)) {
- if (sb->s_root)
- return true;
- up_read(&sb->s_umount);
- }
-
- put_super(sb);
- return false;
-}
-
+ static long writeback_chunk_size(struct backing_dev_info *bdi,
+ struct wb_writeback_work *work)
+ {
+ long pages;
+
+ /*
+ * WB_SYNC_ALL mode does livelock avoidance by syncing dirty
+ * inodes/pages in one big loop. Setting wbc.nr_to_write=LONG_MAX
+ * here avoids calling into writeback_inodes_wb() more than once.
+ *
+ * The intended call sequence for WB_SYNC_ALL writeback is:
+ *
+ * wb_writeback()
+ * writeback_sb_inodes() <== called only once
+ * write_cache_pages() <== called once for each inode
+ * (quickly) tag currently dirty pages
+ * (maybe slowly) sync all tagged pages
+ */
+ if (work->sync_mode == WB_SYNC_ALL || work->tagged_writepages)
+ pages = LONG_MAX;
+ else {
+ pages = min(bdi->avg_write_bandwidth / 2,
+ global_dirty_limit / DIRTY_SCOPE);
+ pages = min(pages, work->nr_pages);
+ pages = round_down(pages + MIN_WRITEBACK_PAGES,
+ MIN_WRITEBACK_PAGES);
+ }
+
+ return pages;
+ }
+
/*
* Write a portion of b_io inodes which belong to @sb.
*
@@@ -559,40 -643,41 +617,41 @@@ static long __writeback_inodes_wb(struc
struct inode *inode = wb_inode(wb->b_io.prev);
struct super_block *sb = inode->i_sb;
- if (!pin_sb_for_writeback(sb)) {
+ if (!grab_super_passive(sb)) {
- requeue_io(inode);
+ requeue_io(inode, wb);
continue;
}
- ret = writeback_sb_inodes(sb, wb, wbc, false);
+ wrote += writeback_sb_inodes(sb, wb, work);
drop_super(sb);
- if (ret)
- break;
+ /* refer to the same tests at the end of writeback_sb_inodes */
+ if (wrote) {
+ if (time_is_before_jiffies(start_time + HZ / 10UL))
+ break;
+ if (work->nr_pages <= 0)
+ break;
+ }
}
- spin_unlock(&inode_wb_list_lock);
/* Leave any unwritten inodes on b_io */
+ return wrote;
}
- static void __writeback_inodes_sb(struct super_block *sb,
- struct bdi_writeback *wb, struct writeback_control *wbc)
+ long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages)
{
- WARN_ON(!rwsem_is_locked(&sb->s_umount));
+ struct wb_writeback_work work = {
+ .nr_pages = nr_pages,
+ .sync_mode = WB_SYNC_NONE,
+ .range_cyclic = 1,
+ };
- spin_lock(&inode_wb_list_lock);
- if (!wbc->for_kupdate || list_empty(&wb->b_io))
- queue_io(wb, wbc->older_than_this);
- writeback_sb_inodes(sb, wb, wbc, true);
- spin_unlock(&inode_wb_list_lock);
- }
+ spin_lock(&wb->list_lock);
+ if (list_empty(&wb->b_io))
+ queue_io(wb, NULL);
+ __writeback_inodes_wb(wb, &work);
+ spin_unlock(&wb->list_lock);
- /*
- * The maximum number of pages to writeout in a single bdi flush/kupdate
- * operation. We do this so we don't hold I_SYNC against an inode for
- * enormous amounts of time, which would block a userspace task which has
- * been forced to throttle against that inode. Also, the code reevaluates
- * the dirty each time it has written this many pages.
- */
- #define MAX_WRITEBACK_PAGES 1024
+ return nr_pages - work.nr_pages;
+ }
static inline bool over_bground_thresh(void)
{
--
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