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From: Artem Bityutskiy <dedekind1@gmail.com>
To: Jens Axboe <axboe@kernel.dk>
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCHv4 09/14] writeback: restructure bdi forker loop a little
Date: Fri, 23 Jul 2010 18:05:49 +0300	[thread overview]
Message-ID: <1279897554-1526-10-git-send-email-dedekind1@gmail.com> (raw)
In-Reply-To: <1279897554-1526-1-git-send-email-dedekind1@gmail.com>

From: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

This patch re-structures the loop which walks bdi a little. This is just a
micro-step towards the coming change where the forker thread will kill the bdi
threads. It should simplify reviewing the following changes, which would
otherwise be larger.

This patch also adds the 'bdi_cap_flush_forker(bdi)' condition check to the
loop. The reason for this is that the forker thread can start _before_ the
'BDI_registered' flag is set (see 'bdi_register()'), so the WARN() statement
will fire for the default bdi. I observed this warning at boot-up.

This patch also amends comments a little.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 mm/backing-dev.c |   28 +++++++++++++++++-----------
 1 files changed, 17 insertions(+), 11 deletions(-)

diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 672c17b..b788b8e 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -348,25 +348,31 @@ static int bdi_forker_thread(void *ptr)
 		 * a thread registered. If so, set that up.
 		 */
 		list_for_each_entry(bdi, &bdi_list, bdi_list) {
-			if (!bdi_cap_writeback_dirty(bdi))
-				continue;
-			if (bdi->wb.task)
-				continue;
-			if (list_empty(&bdi->work_list) &&
-			    !bdi_has_dirty_io(bdi))
+			bool have_dirty_io;
+
+			if (!bdi_cap_writeback_dirty(bdi) ||
+			     bdi_cap_flush_forker(bdi))
 				continue;
 
 			WARN(!test_bit(BDI_registered, &bdi->state),
 			     "bdi %p/%s is not registered!\n", bdi, bdi->name);
 
-			fork = true;
+			have_dirty_io = !list_empty(&bdi->work_list) ||
+					wb_has_dirty_io(&bdi->wb);
 
 			/*
-			 * Set the pending bit - if someone will try to
-			 * unregister this bdi - it'll wait on this bit.
+			 * If the bdi has work to do, but the thread does not
+			 * exist - create it.
 			 */
-			set_bit(BDI_pending, &bdi->state);
-			break;
+			if (!bdi->wb.task && have_dirty_io) {
+				/*
+				 * Set the pending bit - if someone will try to
+				 * unregister this bdi - it'll wait on this bit.
+				 */
+				set_bit(BDI_pending, &bdi->state);
+				fork = true;
+				break;
+			}
 		}
 		spin_unlock_bh(&bdi_lock);
 
-- 
1.7.1.1


  parent reply	other threads:[~2010-07-23 15:09 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-07-23 15:05 [PATCHv4 00/14] kill unnecessary bdi wakeups + cleanups Artem Bityutskiy
2010-07-23 15:05 ` [PATCHv4 01/14] writeback: harmonize writeback threads naming Artem Bityutskiy
2010-07-23 15:05 ` [PATCHv4 02/14] writeback: fix possible race when creating bdi threads Artem Bityutskiy
2010-07-23 15:05 ` [PATCHv4 03/14] writeback: do not lose wake-ups in the forker thread - 1 Artem Bityutskiy
2010-07-23 15:05 ` [PATCHv4 04/14] writeback: do not lose wake-ups in the forker thread - 2 Artem Bityutskiy
2010-07-23 15:05 ` [PATCHv4 05/14] writeback: do not lose wake-ups in bdi threads Artem Bityutskiy
2010-07-23 15:05 ` [PATCHv4 06/14] writeback: simplify bdi code a little Artem Bityutskiy
2010-07-23 15:05 ` [PATCHv4 07/14] writeback: do not remove bdi from bdi_list Artem Bityutskiy
2010-07-23 15:05 ` [PATCHv4 08/14] writeback: move last_active to bdi Artem Bityutskiy
2010-07-23 15:05 ` Artem Bityutskiy [this message]
2010-07-23 15:05 ` [PATCHv4 10/14] writeback: move bdi threads exiting logic to the forker thread Artem Bityutskiy
2010-07-23 16:23   ` Christoph Hellwig
2010-07-24  5:55     ` Artem Bityutskiy
2010-07-24  5:55       ` Artem Bityutskiy
2010-07-23 15:05 ` [PATCHv4 11/14] writeback: prevent unnecessary bdi threads wakeups Artem Bityutskiy
2010-07-23 15:05 ` [PATCHv4 12/14] writeback: optimize periodic bdi thread wakeups Artem Bityutskiy
2010-07-23 16:28   ` Christoph Hellwig
2010-07-24  6:00     ` Artem Bityutskiy
2010-07-23 15:05 ` [PATCHv4 13/14] writeback: remove unnecessary init_timer call Artem Bityutskiy
2010-07-23 16:28   ` Christoph Hellwig
2010-07-23 15:05 ` [PATCHv4 14/14] writeback: add new tracepoints Artem Bityutskiy
2010-07-23 16:29   ` Christoph Hellwig
2010-07-24  6:01     ` Artem Bityutskiy

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