path: root/fs/fs-writeback.c
diff options
authorJan Kara <jack@suse.cz>2010-09-21 11:51:01 +0200
committerJens Axboe <jaxboe@fusionio.com>2010-09-22 09:48:47 +0200
commit692ebd17c2905313fff3c504c249c6a0faad16ec (patch)
tree656c80512505d5b117bd01e25d66d88d7cfe9851 /fs/fs-writeback.c
parent371d217ee1ff8b418b8f73fb2a34990f951ec2d4 (diff)
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 <jack@suse.cz> Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Diffstat (limited to 'fs/fs-writeback.c')
1 files changed, 21 insertions, 2 deletions
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 81e086d8aa5..5581122bd2c 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -52,8 +52,6 @@ struct wb_writeback_work {
#include <trace/events/writeback.h>
-#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)