block: Fix oops in locked_inode_to_wb_and_lock_list()
When block device is closed, we call inode_detach_wb() in __blkdev_put()
which sets inode->i_wb to NULL. That is contrary to expectations that
inode->i_wb stays valid once set during the whole inode's lifetime and
leads to oops in wb_get() in locked_inode_to_wb_and_lock_list() because
inode_to_wb() returned NULL.
The reason why we called inode_detach_wb() is not valid anymore though.
BDI is guaranteed to stay along until we call bdi_put() from
bdev_evict_inode() so we can postpone calling inode_detach_wb() to that
moment.
Also add a warning to catch if someone uses inode_detach_wb() in a
dangerous way.
Change-Id: Idd7ddbc8120381b1649c4f82e2e8447c66b7ae4c
Reported-by: Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jens Axboe <axboe@fb.com>
Git-commit: f759741d9d913eb57784a94b9bca78b376fc26a9
Git-repo: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git
Signed-off-by: Ritesh Harjani <riteshh@codeaurora.org>
diff --git a/fs/block_dev.c b/fs/block_dev.c
index 8a55e84..9900693 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -629,6 +629,8 @@
spin_lock(&bdev_lock);
list_del_init(&bdev->bd_list);
spin_unlock(&bdev_lock);
+ /* Detach inode from wb early as bdi_put() may free bdi->wb */
+ inode_detach_wb(inode);
if (bdev->bd_bdi != &noop_backing_dev_info) {
bdi_put(bdev->bd_bdi);
bdev->bd_bdi = &noop_backing_dev_info;
@@ -1618,12 +1620,6 @@
kill_bdev(bdev);
bdev_write_inode(bdev);
- /*
- * Detaching bdev inode from its wb in __destroy_inode()
- * is too late: the queue which embeds its bdi (along with
- * root wb) can be gone as soon as we put_disk() below.
- */
- inode_detach_wb(bdev->bd_inode);
}
if (bdev->bd_contains == bdev) {
if (disk->fops->release)
diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index 797100e..9a8eb83 100644
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -224,6 +224,7 @@
static inline void inode_detach_wb(struct inode *inode)
{
if (inode->i_wb) {
+ WARN_ON_ONCE(!(inode->i_state & I_CLEAR));
wb_put(inode->i_wb);
inode->i_wb = NULL;
}