fallthru: ext2 fallthru support
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From: Valerie Aurora on 4 Aug 2010 18:50 On Wed, Aug 04, 2010 at 04:44:10PM +0200, Miklos Szeredi wrote: > On Tue, 15 Jun 2010, Valerie Aurora wrote: > > Add support for fallthru directory entries to ext2. > > If a previously used ext2 filesystem with is mounted again then > fallthroughs don't appear to work as expected. Stat returns ENOENT > for these entries. > > Can't see anything obviously wrong with the code. Hm, I wrote one test case for this that worked (attached). Can you give me more details on your test case? Thanks, -VAL
From: Miklos Szeredi on 5 Aug 2010 06:40 On Wed, 4 Aug 2010, Valerie Aurora wrote: > --zYM0uCDKw75PZbzx > Content-Type: text/plain; charset=us-ascii > Content-Disposition: inline > > On Wed, Aug 04, 2010 at 04:44:10PM +0200, Miklos Szeredi wrote: > > On Tue, 15 Jun 2010, Valerie Aurora wrote: > > > Add support for fallthru directory entries to ext2. > > > > If a previously used ext2 filesystem with is mounted again then > > fallthroughs don't appear to work as expected. Stat returns ENOENT > > for these entries. > > > > Can't see anything obviously wrong with the code. > > Hm, I wrote one test case for this that worked (attached). Can you > give me more details on your test case? Thanks, uml:~# mount -oloop -r ext3-2.img /mnt/img/ uml:~# mount -oloop -r ext3.img /mnt/img/ uml:~# losetup -f ovl.img uml:~# mmount -b 8 -t ext2 /dev/loop2 /mnt/img/ uml:~# "ls" /mnt/img bunion lost+found union uml:~# "ls" /mnt/img/union 1 2 3 uml:~# "ls" /mnt/img/union/1 a x uml:~# umount /mnt/img/ uml:~# mmount -b 8 -t ext2 /dev/loop2 /mnt/img/ uml:~# ls -l /mnt/img/ total 14 drwxr-xr-x 2 root root 1024 Aug 5 09:56 bunion drwx------ 2 root root 12288 Aug 5 09:41 lost+found drwxr-xr-x 3 root root 1024 Aug 5 09:56 union uml:~# ls -l /mnt/img/union/ ls: cannot access /mnt/img/union/3: No such file or directory ls: cannot access /mnt/img/union/2: No such file or directory total 1 drwxr-xr-x 2 root root 1024 Aug 5 09:56 1 ?????????? ? ? ? ? ? 2 ?????????? ? ? ? ? ? 3 uml:~# ls -l /mnt/img/union/1 ls: cannot access /mnt/img/union/1/a: No such file or directory ls: cannot access /mnt/img/union/1/x: No such file or directory total 0 ?????????? ? ? ? ? ? a ?????????? ? ? ? ? ? x uml:~# Thanks, Miklos -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Miklos Szeredi on 5 Aug 2010 07:20 On Wed, 4 Aug 2010, Valerie Aurora wrote: > > Another idea is to use an internal inode and make all fallthroughs be > > hard links to that. > > > > I think the same would work for whiteouts as well. I don't like the > > fact that whiteouts are invisible even when not mounted as part of a > > union. > > I don't know if this helps, but I just wrote support for removing ext2 > whiteouts and fallthrus using tune2fs and e2fsck. I think this does > what people want from a "visible" whiteout feature without adding more > complexity to the VFS. It also takes away all consideration of race > conditions and dentry conversion that happens with online removal of > whiteouts and fallthrus. > > What are your thoughts on what a visible whiteout/fallthru would look > like? Best would be if it didn't need any modification to filesystems. All this having to upgrade util-linux, e2fsprogs, having incompatible filesystem features is a pain for users (just been through that). What we already have in most filesystems: - extended attributes, e.g. use the system.union.* namespace and denote whiteouts and falltroughs with such an attribute - hard links to make sure a separate inode is not necessary for each whiteout/fallthrough entry - some way for the user to easily identify such files when not mounted as part of a union e.g. make it a symlink pointing to "(deleted)" or whatever Later the extended attributes can also be used for other things like e.g. chmod()/chown() only copying up metadata, not data, and indicating that data is still found on the lower layers. Miklos -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Valerie Aurora on 5 Aug 2010 19:40 On Thu, Aug 05, 2010 at 12:36:55PM +0200, Miklos Szeredi wrote: > On Wed, 4 Aug 2010, Valerie Aurora wrote: > > --zYM0uCDKw75PZbzx > > Content-Type: text/plain; charset=us-ascii > > Content-Disposition: inline > > > > On Wed, Aug 04, 2010 at 04:44:10PM +0200, Miklos Szeredi wrote: > > > On Tue, 15 Jun 2010, Valerie Aurora wrote: > > > > Add support for fallthru directory entries to ext2. > > > > > > If a previously used ext2 filesystem with is mounted again then > > > fallthroughs don't appear to work as expected. Stat returns ENOENT > > > for these entries. > > > > > > Can't see anything obviously wrong with the code. > > > > Hm, I wrote one test case for this that worked (attached). Can you > > give me more details on your test case? Thanks, Cool, thanks. Yes, I suppose the fallthrus should be ignored if they don't fall through to anything. If I do a proper lookup for d_ino, I can kill two birds with one stone, since that will tell us whether there is anything below the fallthru and thus whether to return this directory entry. -VAL > uml:~# mount -oloop -r ext3-2.img /mnt/img/ > uml:~# mount -oloop -r ext3.img /mnt/img/ > uml:~# losetup -f ovl.img > uml:~# mmount -b 8 -t ext2 /dev/loop2 /mnt/img/ > uml:~# "ls" /mnt/img > bunion lost+found union > uml:~# "ls" /mnt/img/union > 1 2 3 > uml:~# "ls" /mnt/img/union/1 > a x > uml:~# umount /mnt/img/ > uml:~# mmount -b 8 -t ext2 /dev/loop2 /mnt/img/ > uml:~# ls -l /mnt/img/ > total 14 > drwxr-xr-x 2 root root 1024 Aug 5 09:56 bunion > drwx------ 2 root root 12288 Aug 5 09:41 lost+found > drwxr-xr-x 3 root root 1024 Aug 5 09:56 union > uml:~# ls -l /mnt/img/union/ > ls: cannot access /mnt/img/union/3: No such file or directory > ls: cannot access /mnt/img/union/2: No such file or directory > total 1 > drwxr-xr-x 2 root root 1024 Aug 5 09:56 1 > ?????????? ? ? ? ? ? 2 > ?????????? ? ? ? ? ? 3 > uml:~# ls -l /mnt/img/union/1 > ls: cannot access /mnt/img/union/1/a: No such file or directory > ls: cannot access /mnt/img/union/1/x: No such file or directory > total 0 > ?????????? ? ? ? ? ? a > ?????????? ? ? ? ? ? x > uml:~# > > Thanks, > Miklos -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Miklos Szeredi on 6 Aug 2010 04:20 On Thu, 5 Aug 2010, Valerie Aurora wrote: > On Thu, Aug 05, 2010 at 12:36:55PM +0200, Miklos Szeredi wrote: > > On Wed, 4 Aug 2010, Valerie Aurora wrote: > > > --zYM0uCDKw75PZbzx > > > Content-Type: text/plain; charset=us-ascii > > > Content-Disposition: inline > > > > > > On Wed, Aug 04, 2010 at 04:44:10PM +0200, Miklos Szeredi wrote: > > > > On Tue, 15 Jun 2010, Valerie Aurora wrote: > > > > > Add support for fallthru directory entries to ext2. > > > > > > > > If a previously used ext2 filesystem with is mounted again then > > > > fallthroughs don't appear to work as expected. Stat returns ENOENT > > > > for these entries. > > > > > > > > Can't see anything obviously wrong with the code. > > > > > > Hm, I wrote one test case for this that worked (attached). Can you > > > give me more details on your test case? Thanks, > > Cool, thanks. Yes, I suppose the fallthrus should be ignored if they > don't fall through to anything. That's not the case here. They _should_ fall through to ext3.img, yet apparently after ovl.img being mounted again they don't seem to work. Note, ovl.img starts out as a completely empty filesystem. The difference between your test case and mine mitght be that yours not only reads the directory but stats the files as well, while mine does not. Thanks, Miklos > > > uml:~# mount -oloop -r ext3-2.img /mnt/img/ > > uml:~# mount -oloop -r ext3.img /mnt/img/ > > uml:~# losetup -f ovl.img > > uml:~# mmount -b 8 -t ext2 /dev/loop2 /mnt/img/ > > uml:~# "ls" /mnt/img > > bunion lost+found union > > uml:~# "ls" /mnt/img/union > > 1 2 3 > > uml:~# "ls" /mnt/img/union/1 > > a x > > uml:~# umount /mnt/img/ > > uml:~# mmount -b 8 -t ext2 /dev/loop2 /mnt/img/ > > uml:~# ls -l /mnt/img/ > > total 14 > > drwxr-xr-x 2 root root 1024 Aug 5 09:56 bunion > > drwx------ 2 root root 12288 Aug 5 09:41 lost+found > > drwxr-xr-x 3 root root 1024 Aug 5 09:56 union > > uml:~# ls -l /mnt/img/union/ > > ls: cannot access /mnt/img/union/3: No such file or directory > > ls: cannot access /mnt/img/union/2: No such file or directory > > total 1 > > drwxr-xr-x 2 root root 1024 Aug 5 09:56 1 > > ?????????? ? ? ? ? ? 2 > > ?????????? ? ? ? ? ? 3 > > uml:~# ls -l /mnt/img/union/1 > > ls: cannot access /mnt/img/union/1/a: No such file or directory > > ls: cannot access /mnt/img/union/1/x: No such file or directory > > total 0 > > ?????????? ? ? ? ? ? a > > ?????????? ? ? ? ? ? x > > uml:~# > > > > Thanks, > > Miklos > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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