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Message-ID: <20090309045953.GA26853@skywalker> Date: Mon, 9 Mar 2009 10:29:53 +0530 From: "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com> To: Eric Sandeen <sandeen@...hat.com> Cc: ext4 development <linux-ext4@...r.kernel.org>, David Dindorp <ddi@...ex.dk> Subject: Re: [PATCH] fix header check in ext4_ext_search_right() for deep extent trees. On Fri, Mar 06, 2009 at 02:50:51PM -0600, Eric Sandeen wrote: > This should resolve kernel.org bugzilla 12821 > > I've not actually crafted a workload to exercise this code; > this is from inspection... > > The ext4_ext_search_right() function is confusing; it uses a > "depth" variable which is 0 at the root and maximum at the leaves, > but the on-disk metadata uses a "depth" (actually eh_depth) which > is opposite: maximum at the root, and 0 at the leaves. > > The ext4_ext_check_header() function is given a depth and checks > the header agaisnt that depth; it expects the on-disk semantics, > but we are giving it the opposite in the while loop in this > function. We should be giving it the on-disk notion of "depth" > which we can get from (p_depth - depth) - and if you look, the last > (more commonly hit) call to ext4_ext_check_header() does just this. Correct. Few lines below we are passing the right depth when verifying the leaf blocks. So I guess it was a coding error. > > Sending in the wrong depth results in (incorrect) messages > about corruption: > > EXT4-fs error (device sdb1): ext4_ext_search_right: bad header > in inode #2621457: unexpected eh_depth - magic f30a, entries 340, > max 340(0), depth 1(2) > > Reported-by: David Dindorp <ddi@...ex.dk> > Signed-off-by: Eric Sandeen <sandeen@...hat.com> Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com> > -- > > Index: linux-2.6/fs/ext4/extents.c > =================================================================== > --- linux-2.6.orig/fs/ext4/extents.c > +++ linux-2.6/fs/ext4/extents.c > @@ -1122,7 +1122,8 @@ ext4_ext_search_right(struct inode *inod > struct ext4_extent_idx *ix; > struct ext4_extent *ex; > ext4_fsblk_t block; > - int depth, ee_len; > + int depth; /* Note, NOT eh_depth; depth from top of tree */ > + int ee_len; > > BUG_ON(path == NULL); > depth = path->p_depth; > @@ -1179,7 +1180,8 @@ got_index: > if (bh == NULL) > return -EIO; > eh = ext_block_hdr(bh); > - if (ext4_ext_check_header(inode, eh, depth)) { > + /* subtract from p_depth to get proper eh_depth */ > + if (ext4_ext_check_header(inode, eh, path->p_depth - depth)) { > put_bh(bh); > return -EIO; > } > -aneesh -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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