On Wed 29-09-10 10:19:36, Christoph Hellwig wrote: > --- > From: Christoph Hellwig <[email protected]> > Subject: [PATCH] writeback: always use sb->s_bdi for writeback purposes > ... > The one exception for now is the block device filesystem which really > wants different writeback contexts for it's different (internal) inodes > to handle the writeout more efficiently. For now we do this with > a hack in fs-writeback.c because we're so late in the cycle, but in > the future I plan to replace this with a superblock method that allows > for multiple writeback contexts per filesystem. Another exception I know about is mtd_inodefs filesystem (drivers/mtd/mtdchar.c).
> Signed-off-by: Christoph Hellwig <[email protected]> > > Index: linux-2.6/fs/fs-writeback.c > =================================================================== > --- linux-2.6.orig/fs/fs-writeback.c 2010-09-29 16:58:41.750557721 +0900 > +++ linux-2.6/fs/fs-writeback.c 2010-09-29 17:11:35.040557719 +0900 > @@ -72,22 +72,10 @@ int writeback_in_progress(struct backing > 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; > + if (strcmp(sb->s_type->name, "bdev") == 0) > + return inode->i_mapping->backing_dev_info; > + return sb->s_bdi; So at least here you'd need also add a similar exception for "mtd_inodefs". Because of these exeptions I've chosen the (sb->s_bdi && sb->s_bdi != &noop_backing_dev_info) check rather than your exception based check. All in all I don't care much what ends up in the kernel as it's just a temporary solution... Also I've added the warning to catch situations where inodes would get filed to a different backing device after the patch. So far the reported warnings were harmless but still I'm more comfortable when it's there because otherwise we can so easily miss some device-driver-invented filesystem like mtd_inodefs which would break silently after the change... Honza -- Jan Kara <[email protected]> SUSE Labs, CR _______________________________________________ kernel mailing list [email protected] https://admin.fedoraproject.org/mailman/listinfo/kernel
