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Message-Id: <1239192016-19857-14-git-send-email-jens.axboe@oracle.com>
Date: Wed, 8 Apr 2009 14:00:16 +0200
From: Jens Axboe <jens.axboe@...cle.com>
To: linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Cc: chris.mason@...cle.com, david@...morbit.com, hch@...radead.org,
akpm@...ux-foundation.org, jack@...e.cz,
Jens Axboe <jens.axboe@...cle.com>
Subject: [PATCH 13/13] writeback: ensure consistency for generic_sync_sb_inodes() with WB_SYNC_ALL
If WB_SYNC_ALL is given, we must block waiting for any bdi/wb to become
available and flush our data. Switch the bdi_list protection to SRCU
instead of RCU so that we can do that.
Signed-off-by: Jens Axboe <jens.axboe@...cle.com>
---
fs/fs-writeback.c | 49 +++++++++++++++++++++++++++++--------------
include/linux/backing-dev.h | 12 ++++++++-
mm/backing-dev.c | 23 ++++++++++++--------
mm/page-writeback.c | 4 +-
4 files changed, 59 insertions(+), 29 deletions(-)
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 1d25d3a..0492399 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -50,11 +50,18 @@ static void generic_sync_wb_inodes(struct bdi_writeback *wb,
* unless they implement their own. Which is somewhat inefficient, as this
* may prevent concurrent writeback against multiple devices.
*/
-static int writeback_acquire(struct bdi_writeback *wb)
+static bool writeback_acquire(struct bdi_writeback *wb, int wait)
{
struct backing_dev_info *bdi = wb->bdi;
- return !test_and_set_bit(wb->nr, &bdi->wb_active);
+ if (!test_and_set_bit(wb->nr, &bdi->wb_active))
+ return 1;
+ if (!wait)
+ return 0;
+
+ wait_on_bit_lock(&bdi->wb_active, wb->nr, bdi_sched_wait,
+ TASK_UNINTERRUPTIBLE);
+ return 1;
}
/**
@@ -82,12 +89,15 @@ static void writeback_release(struct bdi_writeback *wb)
}
static void wb_start_writeback(struct bdi_writeback *wb, struct super_block *sb,
- long nr_pages)
+ long nr_pages, int wait)
{
if (!wb_has_dirty_io(wb))
return;
- if (writeback_acquire(wb)) {
+ /*
+ * Wait is set, block waiting for the device to become available
+ */
+ if (writeback_acquire(wb, wait)) {
wb->nr_pages = nr_pages;
wb->sb = sb;
@@ -100,7 +110,7 @@ static void wb_start_writeback(struct bdi_writeback *wb, struct super_block *sb,
}
int bdi_start_writeback(struct backing_dev_info *bdi, struct super_block *sb,
- long nr_pages)
+ long nr_pages, int wait)
{
struct bdi_writeback *wb;
@@ -114,14 +124,14 @@ int bdi_start_writeback(struct backing_dev_info *bdi, struct super_block *sb,
}
if (!bdi_wblist_needs_lock(bdi))
- wb_start_writeback(&bdi->wb, sb, nr_pages);
+ wb_start_writeback(&bdi->wb, sb, nr_pages, wait);
else {
int idx;
idx = srcu_read_lock(&bdi->srcu);
list_for_each_entry_rcu(wb, &bdi->wb_list, list)
- wb_start_writeback(wb, sb, nr_pages);
+ wb_start_writeback(wb, sb, nr_pages, wait);
srcu_read_unlock(&bdi->srcu, idx);
}
@@ -244,7 +254,7 @@ long wb_do_writeback(struct bdi_writeback *wb)
* pdflush style writeout.
*
*/
- if (writeback_acquire(wb))
+ if (writeback_acquire(wb, 0))
nr_pages = wb_kupdated(wb);
else
nr_pages = wb_writeback(wb);
@@ -295,21 +305,21 @@ int bdi_writeback_task(struct bdi_writeback *wb)
return 0;
}
-void bdi_writeback_all(struct super_block *sb, long nr_pages)
+void bdi_writeback_all(struct super_block *sb, long nr_pages, int wait)
{
struct backing_dev_info *bdi;
+ int idx;
- rcu_read_lock();
-
+ idx = srcu_read_lock(&bdi_srcu);
restart:
list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) {
if (!bdi_has_dirty_io(bdi))
continue;
- if (bdi_start_writeback(bdi, sb, nr_pages))
+ if (bdi_start_writeback(bdi, sb, nr_pages, wait))
goto restart;
}
- rcu_read_unlock();
+ srcu_read_unlock(&bdi_srcu, idx);
}
/*
@@ -828,12 +838,19 @@ void generic_sync_bdi_inodes(struct super_block *sb,
void generic_sync_sb_inodes(struct super_block *sb,
struct writeback_control *wbc)
{
+ const int sync_all = wbc->sync_mode == WB_SYNC_ALL;
+
+ /*
+ * Kick off the specified bdi, if given, or all of them. If sync_all
+ * is true, then this is a blocking operation and we must make sure
+ * to wait for any device that is currently doing a writeback operation.
+ */
if (wbc->bdi)
- bdi_start_writeback(wbc->bdi, sb, 0);
+ bdi_start_writeback(wbc->bdi, sb, 0, sync_all);
else
- bdi_writeback_all(sb, 0);
+ bdi_writeback_all(sb, 0, sync_all);
- if (wbc->sync_mode == WB_SYNC_ALL) {
+ if (sync_all) {
struct inode *inode, *old_inode = NULL;
spin_lock(&inode_lock);
diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index c7c1ed6..8ab2429 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -14,6 +14,7 @@
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/srcu.h>
+#include <linux/sched.h>
#include <asm/atomic.h>
struct page;
@@ -105,15 +106,22 @@ int bdi_register(struct backing_dev_info *bdi, struct device *parent,
int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev);
void bdi_unregister(struct backing_dev_info *bdi);
int bdi_start_writeback(struct backing_dev_info *bdi, struct super_block *sb,
- long nr_pages);
+ long nr_pages, int wait);
int bdi_writeback_task(struct bdi_writeback *wb);
-void bdi_writeback_all(struct super_block *sb, long nr_pages);
+void bdi_writeback_all(struct super_block *sb, long nr_pages, int wait);
void bdi_add_default_flusher_task(struct backing_dev_info *bdi);
void bdi_add_flusher_task(struct backing_dev_info *bdi);
int bdi_has_dirty_io(struct backing_dev_info *bdi);
extern spinlock_t bdi_lock;
extern struct list_head bdi_list;
+extern struct srcu_struct bdi_srcu;
+
+static inline int bdi_sched_wait(void *word)
+{
+ schedule();
+ return 0;
+}
static inline int wb_is_default_task(struct bdi_writeback *wb)
{
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 9d6ac11..8ee7b55 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -29,6 +29,7 @@ static struct class *bdi_class;
DEFINE_SPINLOCK(bdi_lock);
LIST_HEAD(bdi_list);
LIST_HEAD(bdi_pending_list);
+struct srcu_struct bdi_srcu;
#ifdef CONFIG_DEBUG_FS
#include <linux/debugfs.h>
@@ -220,10 +221,19 @@ static int __init default_bdi_init(void)
{
int err;
+ err = init_srcu_struct(&bdi_srcu);
+ if (err)
+ return err;
+
err = bdi_init(&default_backing_dev_info);
if (!err)
bdi_register(&default_backing_dev_info, NULL, "default");
+ if (err) {
+ bdi_destroy(&default_backing_dev_info);
+ cleanup_srcu_struct(&bdi_srcu);
+ }
+
return err;
}
subsys_initcall(default_bdi_init);
@@ -473,12 +483,6 @@ static void bdi_add_to_pending(struct rcu_head *head)
wake_up(&default_backing_dev_info.wb.wait);
}
-static int sched_wait(void *word)
-{
- schedule();
- return 0;
-}
-
static void bdi_add_one_flusher_task(struct backing_dev_info *bdi,
int(*func)(struct backing_dev_info *))
{
@@ -513,7 +517,7 @@ static void bdi_add_one_flusher_task(struct backing_dev_info *bdi,
static int flusher_add_helper_block(struct backing_dev_info *bdi)
{
- wait_on_bit_lock(&bdi->state, BDI_pending, sched_wait,
+ wait_on_bit_lock(&bdi->state, BDI_pending, bdi_sched_wait,
TASK_UNINTERRUPTIBLE);
return 0;
}
@@ -620,7 +624,8 @@ static void bdi_wb_shutdown(struct backing_dev_info *bdi)
* If setup is pending, wait for that to complete first
* Make sure nobody finds us on the bdi_list anymore
*/
- wait_on_bit(&bdi->state, BDI_pending, sched_wait, TASK_UNINTERRUPTIBLE);
+ wait_on_bit(&bdi->state, BDI_pending, bdi_sched_wait,
+ TASK_UNINTERRUPTIBLE);
/*
* Make sure nobody finds us on the bdi_list anymore
@@ -633,7 +638,7 @@ static void bdi_wb_shutdown(struct backing_dev_info *bdi)
* Now make sure that anybody who is currently looking at us from
* the bdi_list iteration have exited.
*/
- synchronize_rcu();
+ synchronize_srcu(&bdi_srcu);
/*
* Finally, kill the kernel threads. We don't need to be RCU
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index e71e3c2..bac4ad6 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -581,7 +581,7 @@ static void balance_dirty_pages(struct address_space *mapping)
(!laptop_mode && (global_page_state(NR_FILE_DIRTY)
+ global_page_state(NR_UNSTABLE_NFS)
> background_thresh)))
- bdi_start_writeback(bdi, NULL, 0);
+ bdi_start_writeback(bdi, NULL, 0, 0);
}
void set_page_dirty_balance(struct page *page, int page_mkwrite)
@@ -675,7 +675,7 @@ int wakeup_flusher_threads(long nr_pages)
if (nr_pages == 0)
nr_pages = global_page_state(NR_FILE_DIRTY) +
global_page_state(NR_UNSTABLE_NFS);
- bdi_writeback_all(NULL, nr_pages);
+ bdi_writeback_all(NULL, nr_pages, 0);
return 0;
}
--
1.6.2.2.446.gfbdc0
--
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