From 692ebd17c2905313fff3c504c249c6a0faad16ec Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Tue, 21 Sep 2010 11:51:01 +0200 Subject: [PATCH] bdi: Fix warnings in __mark_inode_dirty for /dev/zero and friends Inodes of devices such as /dev/zero can get dirty for example via utime(2) syscall or due to atime update. Backing device of such inodes (zero_bdi, etc.) is however unable to handle dirty inodes and thus __mark_inode_dirty complains. In fact, inode should be rather dirtied against backing device of the filesystem holding it. This is generally a good rule except for filesystems such as 'bdev' or 'mtd_inodefs'. Inodes in these pseudofilesystems are referenced from ordinary filesystem inodes and carry mapping with real data of the device. Thus for these inodes we have to use inode->i_mapping->backing_dev_info as we did so far. We distinguish these filesystems by checking whether sb->s_bdi points to a non-trivial backing device or not. Example: Assume we have an ext3 filesystem on /dev/sda1 mounted on /. There's a device inode A described by a path "/dev/sdb" on this filesystem. This inode will be dirtied against backing device "8:0" after this patch. bdev filesystem contains block device inode B coupled with our inode A. When someone modifies a page of /dev/sdb, it's B that gets dirtied and the dirtying happens against the backing device "8:16". Thus both inodes get filed to a correct bdi list. Cc: stable@kernel.org Signed-off-by: Jan Kara Signed-off-by: Jens Axboe --- fs/fs-writeback.c | 23 +++++++++++++++++++++-- 1 file changed, 21 insertions(+), 2 deletions(-) diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index 81e086d8aa57..5581122bd2c0 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -52,8 +52,6 @@ struct wb_writeback_work { #define CREATE_TRACE_POINTS #include -#define inode_to_bdi(inode) ((inode)->i_mapping->backing_dev_info) - /* * We don't actually have pdflush, but this one is exported though /proc... */ @@ -71,6 +69,27 @@ int writeback_in_progress(struct backing_dev_info *bdi) return test_bit(BDI_writeback_running, &bdi->state); } +static inline struct backing_dev_info *inode_to_bdi(struct inode *inode) +{ + struct super_block *sb = inode->i_sb; + struct backing_dev_info *bdi = inode->i_mapping->backing_dev_info; + + /* + * For inodes on standard filesystems, we use superblock's bdi. For + * inodes on virtual filesystems, we want to use inode mapping's bdi + * because they can possibly point to something useful (think about + * block_dev filesystem). + */ + if (sb->s_bdi && sb->s_bdi != &noop_backing_dev_info) { + /* Some device inodes could play dirty tricks. Catch them... */ + WARN(bdi != sb->s_bdi && bdi_cap_writeback_dirty(bdi), + "Dirtiable inode bdi %s != sb bdi %s\n", + bdi->name, sb->s_bdi->name); + return sb->s_bdi; + } + return bdi; +} + static void bdi_queue_work(struct backing_dev_info *bdi, struct wb_writeback_work *work) {