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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 /scripts
parent371d217ee1ff8b418b8f73fb2a34990f951ec2d4 (diff)
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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>
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