On Wed 12-03-08 02:42:46, Duane Griffin wrote: > On Tue, Mar 11, 2008 at 04:11:23PM +0100, Jan Kara wrote: > > Actually, this is nastier than it looks - currently fs, asks > > ext3_sb_getblk() for block 'a' and it gets buffer head with b_blocknr == 'b' > > instead. > > Note that it will be a different device as well, in the case of an > external journal. > > > So when remounting you'd have to rewrite these buffers with > > original block numbers which is not really possible. So I think > > remapping will have to be solved differently, like providing buffer > > head with correct b_blocknr but taking care when reading data to it and > > reading them from elsewhere. Actually, this has to be done anyway > > because JBD escapes data in the journal and you have to do unescaping > > when reading data... > > Hmm, I'll think about this and try to get something working. As a quick > proof-of-concept hack, getting both buffers then overwriting the fs > block's data with the unescaped journal data should do the trick, right? Yes, it should, but you should take care for users that do things like: getblk(a) ll_rw_block(READ, a) or even getblk(a) submit_bh(a) I'm not sure if there are any in ext3/ext4 but it definitely needs checking. Honza -- Jan Kara <jack@xxxxxxx> SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
