block: Fix oops in locked_inode_to_wb_and_lock_list() (f759741d) · Commits · 戴 / test

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. 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>

fs/block_dev.c

+2 −6

Original line number	Diff line number	Diff line
		@@ -885,6 +885,8 @@ static void bdev_evict_inode(struct inode *inode)
		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;
		@@ -1875,12 +1877,6 @@ static void __blkdev_put(struct block_device *bdev, fmode_t mode, int for_part)
		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)

include/linux/writeback.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -237,6 +237,7 @@ static inline void inode_attach_wb(struct inode inode, struct page page)
		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;
		}

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