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Message-ID: <503DB3E8.1000308@cn.fujitsu.com>
Date: Wed, 29 Aug 2012 14:17:12 +0800
From: Miao Xie <miaox@...fujitsu.com>
To: Linux Kernel <linux-kernel@...r.kernel.org>,
Linux Btrfs <linux-btrfs@...r.kernel.org>,
Linux Fsdevel <linux-fsdevel@...r.kernel.org>,
Linux Ext4 <linux-ext4@...r.kernel.org>
CC: viro <viro@...iv.linux.org.uk>,
Christoph Hellwig <hch@...radead.org>,
Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 1/2 RESEND] vfs: re-implement writeback_inodes_sb(_nr)_if_idle()
and rename them
writeback_inodes_sb(_nr)_if_idle() is re-implemented by replacing down_read()
with down_read_trylock() because
- If ->s_umount is write locked, then the sb is not idle. That is
writeback_inodes_sb(_nr)_if_idle() needn't wait for the lock.
- writeback_inodes_sb(_nr)_if_idle() grabs s_umount lock when it want to start
writeback, it may bring us deadlock problem when doing umount.
(Ex. Btrfs has such a problem, see the following URL
http://marc.info/?l=linux-btrfs&m=133540923510561&w=2)
The name of these two functions is cumbersome, so rename them to
try_to_writeback_inodes_sb(_nr).
This idea came from Christoph Hellwig.
Some code is from the patch of Kamal Mostafa.
Signed-off-by: Miao Xie <miaox@...fujitsu.com>
---
Many users who use btrfs met the deadlock problem caused by writeback_inodes_sb(_nr)_if_idle(),
so I send this patch again and hope it will be received as soon as possible if nobody objects.
---
fs/btrfs/extent-tree.c | 4 ++--
fs/ext4/inode.c | 2 +-
fs/fs-writeback.c | 45 ++++++++++++++++++++-------------------------
include/linux/writeback.h | 6 +++---
4 files changed, 26 insertions(+), 31 deletions(-)
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 4e1b153..175d802 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -3706,8 +3706,8 @@ static void shrink_delalloc(struct btrfs_root *root, u64 to_reclaim, u64 orig,
while (delalloc_bytes && loops < 3) {
max_reclaim = min(delalloc_bytes, to_reclaim);
nr_pages = max_reclaim >> PAGE_CACHE_SHIFT;
- writeback_inodes_sb_nr_if_idle(root->fs_info->sb, nr_pages,
- WB_REASON_FS_FREE_SPACE);
+ try_to_writeback_inodes_sb_nr(root->fs_info->sb, nr_pages,
+ WB_REASON_FS_FREE_SPACE);
spin_lock(&space_info->lock);
if (space_info->bytes_used + space_info->bytes_reserved +
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index dff171c..33ff5b5 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -2476,7 +2476,7 @@ static int ext4_nonda_switch(struct super_block *sb)
* start pushing delalloc when 1/2 of free blocks are dirty.
*/
if (free_blocks < 2 * dirty_blocks)
- writeback_inodes_sb_if_idle(sb, WB_REASON_FS_FREE_SPACE);
+ try_to_writeback_inodes_sb(sb, WB_REASON_FS_FREE_SPACE);
return 0;
}
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index be3efc4..20a3509 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -1316,7 +1316,6 @@ void writeback_inodes_sb_nr(struct super_block *sb,
bdi_queue_work(sb->s_bdi, &work);
wait_for_completion(&done);
}
-EXPORT_SYMBOL(writeback_inodes_sb_nr);
/**
* writeback_inodes_sb - writeback dirty inodes from given super_block
@@ -1334,47 +1333,43 @@ void writeback_inodes_sb(struct super_block *sb, enum wb_reason reason)
EXPORT_SYMBOL(writeback_inodes_sb);
/**
- * writeback_inodes_sb_if_idle - start writeback if none underway
+ * try_to_writeback_inodes_sb_nr - try to start writeback if none underway
* @sb: the superblock
- * @reason: reason why some writeback work was initiated
+ * @nr: the number of pages to write
+ * @reason: the reason of writeback
*
- * Invoke writeback_inodes_sb if no writeback is currently underway.
+ * Invoke writeback_inodes_sb_nr if no writeback is currently underway.
* Returns 1 if writeback was started, 0 if not.
*/
-int writeback_inodes_sb_if_idle(struct super_block *sb, enum wb_reason reason)
+int try_to_writeback_inodes_sb_nr(struct super_block *sb,
+ unsigned long nr,
+ enum wb_reason reason)
{
- if (!writeback_in_progress(sb->s_bdi)) {
- down_read(&sb->s_umount);
- writeback_inodes_sb(sb, reason);
- up_read(&sb->s_umount);
+ if (writeback_in_progress(sb->s_bdi))
return 1;
- } else
+
+ if (!down_read_trylock(&sb->s_umount))
return 0;
+
+ writeback_inodes_sb_nr(sb, nr, reason);
+ up_read(&sb->s_umount);
+ return 1;
}
-EXPORT_SYMBOL(writeback_inodes_sb_if_idle);
+EXPORT_SYMBOL(try_to_writeback_inodes_sb_nr);
/**
- * writeback_inodes_sb_nr_if_idle - start writeback if none underway
+ * try_to_writeback_inodes_sb - try to 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.
+ * Implement by try_to_writeback_inodes_sb_nr()
* Returns 1 if writeback was started, 0 if not.
*/
-int writeback_inodes_sb_nr_if_idle(struct super_block *sb,
- unsigned long nr,
- enum wb_reason reason)
+int try_to_writeback_inodes_sb(struct super_block *sb, enum wb_reason reason)
{
- if (!writeback_in_progress(sb->s_bdi)) {
- down_read(&sb->s_umount);
- writeback_inodes_sb_nr(sb, nr, reason);
- up_read(&sb->s_umount);
- return 1;
- } else
- return 0;
+ return try_to_writeback_inodes_sb_nr(sb, get_nr_dirty_pages(), reason);
}
-EXPORT_SYMBOL(writeback_inodes_sb_nr_if_idle);
+EXPORT_SYMBOL(try_to_writeback_inodes_sb);
/**
* sync_inodes_sb - sync sb inode pages
diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index 50c3e8f..ecdd0e0 100644
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -87,9 +87,9 @@ int inode_wait(void *);
void writeback_inodes_sb(struct super_block *, enum wb_reason reason);
void writeback_inodes_sb_nr(struct super_block *, unsigned long nr,
enum wb_reason reason);
-int writeback_inodes_sb_if_idle(struct super_block *, enum wb_reason reason);
-int writeback_inodes_sb_nr_if_idle(struct super_block *, unsigned long nr,
- enum wb_reason reason);
+int try_to_writeback_inodes_sb(struct super_block *, enum wb_reason reason);
+int try_to_writeback_inodes_sb_nr(struct super_block *, unsigned long nr,
+ enum wb_reason reason);
void sync_inodes_sb(struct super_block *);
long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages,
enum wb_reason reason);
--
1.6.5.2
--
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