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-btrfsm=133540923510561w=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 mi...@cn.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