diff mbox

[RESEND] vfs: re-implement writeback_inodes_sb(_nr)_if_idle() and rename them

Message ID 50D2E3DF.4010105@cn.fujitsu.com
State Accepted, archived
Headers show

Commit Message

Miao Xie Dec. 20, 2012, 10:09 a.m. UTC 
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. In order to
  fix the problem, ext4 and btrfs implemented their own writeback functions
  instead of writeback_inodes_sb(_nr)_if_idle(), but it introduced the redundant
  code, it is better to implement a new writeback_inodes_sb(_nr)_if_idle().

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@cn.fujitsu.com>
---
 fs/btrfs/extent-tree.c    | 20 +++-----------------
 fs/ext4/inode.c           |  8 ++------
 fs/fs-writeback.c         | 45 ++++++++++++++++++++-------------------------
 include/linux/writeback.h |  6 +++---
 4 files changed, 28 insertions(+), 51 deletions(-)

Comments

David Sterba Dec. 28, 2012, 2:33 p.m. UTC | #1 
On Thu, Dec 20, 2012 at 06:09:35PM +0800, Miao Xie wrote:
> --- a/fs/fs-writeback.c
> +++ b/fs/fs-writeback.c
> @@ -1314,7 +1314,6 @@ 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);

Why do you remove the export? writeback_inodes_sb is exported as well.

Originally the _nr variant has been introduced for btrfs
(3259f8bed2f0f57c2fdcdac1b510c3fa319ef97e) and there are no other users
now, so from that point it would make sense. From the other side, the
change is not strictly necessary for this patch and keeps the writeback
API a bit more flexible. I vote for keeping it.

Otherwise (for the btrfs part),
Tested-by: David Sterba <dsterba@suse.cz>


thanks,
david
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Miao Xie Jan. 10, 2013, 3:24 a.m. UTC | #2 
On Fri, 28 Dec 2012 15:33:38 +0100, David Sterba wrote:
> On Thu, Dec 20, 2012 at 06:09:35PM +0800, Miao Xie wrote:
>> --- a/fs/fs-writeback.c
>> +++ b/fs/fs-writeback.c
>> @@ -1314,7 +1314,6 @@ 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);
> 
> Why do you remove the export? writeback_inodes_sb is exported as well.

As you said below, there is no user now.

> Originally the _nr variant has been introduced for btrfs
> (3259f8bed2f0f57c2fdcdac1b510c3fa319ef97e) and there are no other users
> now, so from that point it would make sense. From the other side, the
> change is not strictly necessary for this patch and keeps the writeback
> API a bit more flexible. I vote for keeping it.

Maybe you are right, I'll send out a new one.

> Otherwise (for the btrfs part),
> Tested-by: David Sterba <dsterba@suse.cz>

Thanks for your test and review.
Miao

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diff mbox

Patch

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index d133edf..994e18e 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -3689,20 +3689,6 @@  static int can_overcommit(struct btrfs_root *root,
 	return 0;
 }
 
-static int writeback_inodes_sb_nr_if_idle_safe(struct super_block *sb,
-					       unsigned long nr_pages,
-					       enum wb_reason reason)
-{
-	if (!writeback_in_progress(sb->s_bdi) &&
-	    down_read_trylock(&sb->s_umount)) {
-		writeback_inodes_sb_nr(sb, nr_pages, reason);
-		up_read(&sb->s_umount);
-		return 1;
-	}
-
-	return 0;
-}
-
 /*
  * shrink metadata reservation for delalloc
  */
@@ -3735,9 +3721,9 @@  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_safe(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);
 
 		/*
 		 * We need to wait for the async pages to actually start before
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index b3c243b..f82d60e 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -2465,12 +2465,8 @@  static int ext4_nonda_switch(struct super_block *sb)
 	/*
 	 * Start pushing delalloc when 1/2 of free blocks are dirty.
 	 */
-	if (dirty_blocks && (free_blocks < 2 * dirty_blocks) &&
-	    !writeback_in_progress(sb->s_bdi) &&
-	    down_read_trylock(&sb->s_umount)) {
-		writeback_inodes_sb(sb, WB_REASON_FS_FREE_SPACE);
-		up_read(&sb->s_umount);
-	}
+	if (dirty_blocks && (free_blocks < 2 * dirty_blocks))
+		try_to_writeback_inodes_sb(sb, WB_REASON_FS_FREE_SPACE);
 
 	if (2 * free_blocks < 3 * dirty_blocks ||
 		free_blocks < (dirty_blocks + EXT4_FREECLUSTERS_WATERMARK)) {
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 3e3422f..9a04ef2 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -1314,7 +1314,6 @@  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
@@ -1332,47 +1331,43 @@  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);