Btrfs: fix inode caching vs tree log

commit 1c70d8fb upstream.

Currently, with inode cache enabled, we will reuse its inode id immediately
after unlinking file, we may hit something like following:

|->iput inode
|->return inode id into inode cache
|->create dir,fsync
|->power off

An easy way to reproduce this problem is:

mkfs.btrfs -f /dev/sdb
mount /dev/sdb /mnt -o inode_cache,commit=100
dd if=/dev/zero of=/mnt/data bs=1M count=10 oflag=sync
inode_id=`ls -i /mnt/data | awk '{print $1}'`
rm -f /mnt/data

i=1
while [ 1 ]
do
        mkdir /mnt/dir_$i
        test1=`stat /mnt/dir_$i | grep Inode: | awk '{print $4}'`
        if [ $test1 -eq $inode_id ]
        then
		dd if=/dev/zero of=/mnt/dir_$i/data bs=1M count=1 oflag=sync
		echo b > /proc/sysrq-trigger
	fi
	sleep 1
        i=$(($i+1))
done

mount /dev/sdb /mnt
umount /dev/sdb
btrfs check /dev/sdb

We fix this problem by adding unlinked inode's id into pinned tree,
and we can not reuse them until committing transaction.
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Wang Shilong <wangsl.fnst@cn.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

fs/btrfs/inode-map.c

@@ -207,24 +207,14 @@ int btrfs_find_free_ino(struct btrfs_root *root, u64 *objectid)
 
 void btrfs_return_ino(struct btrfs_root *root, u64 objectid)
 {
-	struct btrfs_free_space_ctl *ctl = root->free_ino_ctl;
 	struct btrfs_free_space_ctl *pinned = root->free_ino_pinned;
 
 	if (!btrfs_test_opt(root, INODE_MAP_CACHE))
 		return;
-
 again:
 	if (root->cached == BTRFS_CACHE_FINISHED) {
-		__btrfs_add_free_space(ctl, objectid, 1);
+		__btrfs_add_free_space(pinned, objectid, 1);
 	} else {
-		/*
-		 * If we are in the process of caching free ino chunks,
-		 * to avoid adding the same inode number to the free_ino
-		 * tree twice due to cross transaction, we'll leave it
-		 * in the pinned tree until a transaction is committed
-		 * or the caching work is done.
-		 */
-
 		mutex_lock(&root->fs_commit_mutex);
 		spin_lock(&root->cache_lock);
 		if (root->cached == BTRFS_CACHE_FINISHED) {
@@ -236,11 +226,7 @@ void btrfs_return_ino(struct btrfs_root *root, u64 objectid)
 
 		start_caching(root);
 
-		if (objectid <= root->cache_progress ||
-		    objectid >= root->highest_objectid)
-			__btrfs_add_free_space(ctl, objectid, 1);
-		else
-			__btrfs_add_free_space(pinned, objectid, 1);
+		__btrfs_add_free_space(pinned, objectid, 1);
 
 		mutex_unlock(&root->fs_commit_mutex);
 	}