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Date: Tue, 13 Dec 2011 19:33:03 +0800
From: Wu Fengguang <fengguang.wu@...el.com>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: linux-fsdevel@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: [GIT PULL] writeback fixes for 3.2-rc6
Linus,
Please pull 5 writeback fixes, thanks!
- abort write(2) on SIGKILL
- 2 patches to keep system responsive on stalled NFS mount
- 2 comment fixes
The following changes since commit 8748dfae379573cdbea4e765b55e608a1764f918:
Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/aegl/linux (2011-11-28 16:37:35 -0800)
are available in the git repository at:
git://git.kernel.org/pub/scm/linux/kernel/git/wfg/linux.git writeback-for-linus
Jan Kara (1):
fs: Make write(2) interruptible by a fatal signal
Marcos Paulo de Souza (1):
writeback: Fix issue on make htmldocs
Wu Fengguang (3):
writeback: comment on the bdi dirty threshold
writeback: permit through good bdi even when global dirty exceeded
writeback: set max_pause to lowest value on zero bdi_dirty
fs/fs-writeback.c | 5 +++++
mm/filemap.c | 6 ++++--
mm/page-writeback.c | 32 ++++++++++++++++++++++++++++----
3 files changed, 37 insertions(+), 6 deletions(-)
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 73c3992..ac86f8b 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -156,6 +156,7 @@ __bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
* bdi_start_writeback - start writeback
* @bdi: the backing device to write from
* @nr_pages: the number of pages to write
+ * @reason: reason why some writeback work was initiated
*
* Description:
* This does WB_SYNC_NONE opportunistic writeback. The IO is only
@@ -1223,6 +1224,7 @@ static void wait_sb_inodes(struct super_block *sb)
* writeback_inodes_sb_nr - writeback dirty inodes from given super_block
* @sb: the superblock
* @nr: the number of pages to write
+ * @reason: reason why some writeback work initiated
*
* Start writeback on some inodes on this super_block. No guarantees are made
* on how many (if any) will be written, and this function does not wait
@@ -1251,6 +1253,7 @@ EXPORT_SYMBOL(writeback_inodes_sb_nr);
/**
* writeback_inodes_sb - writeback dirty inodes from given super_block
* @sb: the superblock
+ * @reason: reason why some writeback work was initiated
*
* Start writeback on some inodes on this super_block. No guarantees are made
* on how many (if any) will be written, and this function does not wait
@@ -1265,6 +1268,7 @@ EXPORT_SYMBOL(writeback_inodes_sb);
/**
* writeback_inodes_sb_if_idle - start writeback if none underway
* @sb: the superblock
+ * @reason: reason why some writeback work was initiated
*
* Invoke writeback_inodes_sb if no writeback is currently underway.
* Returns 1 if writeback was started, 0 if not.
@@ -1285,6 +1289,7 @@ EXPORT_SYMBOL(writeback_inodes_sb_if_idle);
* writeback_inodes_sb_if_idle - start writeback if none underway
* @sb: the superblock
* @nr: the number of pages to write
+ * @reason: reason why some writeback work was initiated
*
* Invoke writeback_inodes_sb if no writeback is currently underway.
* Returns 1 if writeback was started, 0 if not.
diff --git a/mm/filemap.c b/mm/filemap.c
index c0018f2..c106d3b 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2407,7 +2407,6 @@ static ssize_t generic_perform_write(struct file *file,
iov_iter_count(i));
again:
-
/*
* Bring in the user page that we will copy from _first_.
* Otherwise there's a nasty deadlock on copying from the
@@ -2463,7 +2462,10 @@ again:
written += copied;
balance_dirty_pages_ratelimited(mapping);
-
+ if (fatal_signal_pending(current)) {
+ status = -EINTR;
+ break;
+ }
} while (iov_iter_count(i));
return written ? written : status;
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 7125248..50f0824 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -411,8 +411,13 @@ void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty)
*
* Returns @bdi's dirty limit in pages. The term "dirty" in the context of
* dirty balancing includes all PG_dirty, PG_writeback and NFS unstable pages.
- * And the "limit" in the name is not seriously taken as hard limit in
- * balance_dirty_pages().
+ *
+ * Note that balance_dirty_pages() will only seriously take it as a hard limit
+ * when sleeping max_pause per page is not enough to keep the dirty pages under
+ * control. For example, when the device is completely stalled due to some error
+ * conditions, or when there are 1000 dd tasks writing to a slow 10MB/s USB key.
+ * In the other normal situations, it acts more gently by throttling the tasks
+ * more (rather than completely block them) when the bdi dirty pages go high.
*
* It allocates high/low dirty limits to fast/slow devices, in order to prevent
* - starving fast devices
@@ -594,6 +599,13 @@ static unsigned long bdi_position_ratio(struct backing_dev_info *bdi,
*/
if (unlikely(bdi_thresh > thresh))
bdi_thresh = thresh;
+ /*
+ * It's very possible that bdi_thresh is close to 0 not because the
+ * device is slow, but that it has remained inactive for long time.
+ * Honour such devices a reasonable good (hopefully IO efficient)
+ * threshold, so that the occasional writes won't be blocked and active
+ * writes can rampup the threshold quickly.
+ */
bdi_thresh = max(bdi_thresh, (limit - dirty) / 8);
/*
* scale global setpoint to bdi's:
@@ -977,8 +989,7 @@ static unsigned long bdi_max_pause(struct backing_dev_info *bdi,
*
* 8 serves as the safety ratio.
*/
- if (bdi_dirty)
- t = min(t, bdi_dirty * HZ / (8 * bw + 1));
+ t = min(t, bdi_dirty * HZ / (8 * bw + 1));
/*
* The pause time will be settled within range (max_pause/4, max_pause).
@@ -1136,6 +1147,19 @@ pause:
if (task_ratelimit)
break;
+ /*
+ * In the case of an unresponding NFS server and the NFS dirty
+ * pages exceeds dirty_thresh, give the other good bdi's a pipe
+ * to go through, so that tasks on them still remain responsive.
+ *
+ * In theory 1 page is enough to keep the comsumer-producer
+ * pipe going: the flusher cleans 1 page => the task dirties 1
+ * more page. However bdi_dirty has accounting errors. So use
+ * the larger and more IO friendly bdi_stat_error.
+ */
+ if (bdi_dirty <= bdi_stat_error(bdi))
+ break;
+
if (fatal_signal_pending(current))
break;
}
--
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