[PATCH 11/13] block: Fix oops in locked_inode_to_wb_and_lock_list()
From: Jan Kara <jack@suse.cz>
Date: 2017-02-21 17:09:56
Subsystem:
filesystems (vfs and infrastructure), page cache, the rest · Maintainers:
Alexander Viro, Christian Brauner, Matthew Wilcox, Linus Torvalds
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 <redacted> Signed-off-by: Jan Kara <jack@suse.cz> --- fs/block_dev.c | 8 ++------ include/linux/writeback.h | 1 + 2 files changed, 3 insertions(+), 6 deletions(-)
diff --git a/fs/block_dev.c b/fs/block_dev.c
index 68e855fdce58..a0a8a000bdde 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c@@ -884,6 +884,8 @@ 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); }
@@ -1874,12 +1876,6 @@ 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)
diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index 5527d910ba3d..f1af3f67ce5a 100644
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h@@ -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; }
--
2.10.2