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Commit 90b65ff2 authored by Jan Kara's avatar Jan Kara Committed by Gerrit - the friendly Code Review server
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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: default avatarThiago Jung Bauermann <bauerman@linux.vnet.ibm.com>
Acked-by: default avatarTejun Heo <tj@kernel.org>
Signed-off-by: default avatarJan Kara <jack@suse.cz>
Signed-off-by: default avatarJens 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: default avatarRitesh Harjani <riteshh@codeaurora.org>
parent d8b63b69

fs/block_dev.c

+2 −6
Original line number Original line Diff line number Diff line
@@ -629,6 +629,8 @@ static void bdev_evict_inode(struct inode *inode) 
	spin_lock(&bdev_lock);

	spin_lock(&bdev_lock);

	list_del_init(&bdev->bd_list);

	list_del_init(&bdev->bd_list);

	spin_unlock(&bdev_lock);

	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) {

	if (bdev->bd_bdi != &noop_backing_dev_info) {

		bdi_put(bdev->bd_bdi);

		bdi_put(bdev->bd_bdi);

		bdev->bd_bdi = &noop_backing_dev_info;

		bdev->bd_bdi = &noop_backing_dev_info;
@@ -1618,12 +1620,6 @@ static void __blkdev_put(struct block_device *bdev, fmode_t mode, int for_part) 
		kill_bdev(bdev);

		kill_bdev(bdev);





		bdev_write_inode(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 (bdev->bd_contains == bdev) {

		if (disk->fops->release)

		if (disk->fops->release)

include/linux/writeback.h

+1 −0
Original line number Original line Diff line number Diff line
@@ -224,6 +224,7 @@ static inline void inode_attach_wb(struct inode *inode, struct page *page) 
static inline void inode_detach_wb(struct inode *inode)

static inline void inode_detach_wb(struct inode *inode)

{

{

	if (inode->i_wb) {

	if (inode->i_wb) {

		WARN_ON_ONCE(!(inode->i_state & I_CLEAR));

		wb_put(inode->i_wb);

		wb_put(inode->i_wb);

		inode->i_wb = NULL;

		inode->i_wb = NULL;

	}

	}