Re: ext2 readdir/lookup/check_page behavior
On Nov 14, 2006 13:38 -0600, Eric Sandeen wrote: > Andreas Dilger wrote: > > It would make sense to fix ext2 in the same way. > > I'd suggest bailing out "early" == min(i_size >> blocksize, i_blocks). > > The i_blocks count is an upper limit, because it includes the overhead of > > indirect blocks. Directories cannot be sparse. > > so we could either a) keep processing pages based on i_size, until we > have passed i_blocks, or b) if i_size & i_blocks don't match, > immediately bail out because we know we have found a corrupted inode > (vs. a "normal" unreadable block...) Do we already ext3_error() in this case? That allows the admin to determine the behaviour already. If it is errors=continue or errors=remount-ro then we should continue I think. We might consider the inode fatally corrupted if (i_blocks << 9 < i_size || i_blocks > i_size >> (blockbits - 8) + /* blocks */ i_size >> (blockbits * 2 - 8 - 2) + /* indirect */ i_size >> (blockbits * 3 - 8 - 2) + /* dindirect */ i_size >> (blockbits * 4 - 8 - 2)) /* tindirect */ I think... Trying to account for indirect blocks. It is already given a 100% margin (-8 instead of -9) to cover rounding, EA blocks, some small bugs in block counting, extents format, etc. FYI, the "-2" is 4 bytes/addr. Cheers, Andreas -- Andreas Dilger Principal Software Engineer Cluster File Systems, Inc. - To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: ext2 readdir/lookup/check_page behavior
Andreas Dilger wrote: > On Nov 14, 2006 09:25 -0600, Eric Sandeen wrote: >> has an image with a corrupt directory inode - despite having only 4 blocks, >> it has an extremely large i_size. >> >> It seems odd to me that readdir bails out with an error on the first bad >> page, while lookup keeps trying. Shouldn't these be consistent? And if >> so, which is the desired behavior? > > I'd prefer that readdir _should_ return all of the valid directory blocks > it can find. Otherwise, it makes on average 1/2 of the files in that dir > inaccessible. in the very rare case of corruption, yes... although if ext2 is mounted with anything other than errors=continue the fs is going to turn somewhat useless shortly thereafter anyway. >> Or, perhaps a check high up that says if i_size doesn't correlate to >> i_blocks, this inode is corrupt, and bail out early. > > We did that for ext3, no? Yes, this is similar. In that case we kept trying bad pages until we had exceeded the block count, IIRC. I was considering the possibility of checking blocks vs. size right at the top (ext3_readdir or lookup) and if they don't correspond, don't even bother because the information we're starting with is known to be bad. Looking at this one I wonder if the ext3 fix was too specific/targeted - I'll double check it. > It would make sense to fix ext2 in the same way. > I'd suggest bailing out "early" == min(i_size >> blocksize, i_blocks). > The i_blocks count is an upper limit, because it includes the overhead of > indirect blocks. Directories cannot be sparse. so we could either a) keep processing pages based on i_size, until we have passed i_blocks, or b) if i_size & i_blocks don't match, immediately bail out because we know we have found a corrupted inode (vs. a "normal" unreadable block...) -Eric - To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: ext2 readdir/lookup/check_page behavior
On Nov 14, 2006 09:25 -0600, Eric Sandeen wrote: > has an image with a corrupt directory inode - despite having only 4 blocks, > it has an extremely large i_size. > > It seems odd to me that readdir bails out with an error on the first bad > page, while lookup keeps trying. Shouldn't these be consistent? And if > so, which is the desired behavior? I'd prefer that readdir _should_ return all of the valid directory blocks it can find. Otherwise, it makes on average 1/2 of the files in that dir inaccessible. > Or, perhaps a check high up that says if i_size doesn't correlate to > i_blocks, this inode is corrupt, and bail out early. We did that for ext3, no? It would make sense to fix ext2 in the same way. I'd suggest bailing out "early" == min(i_size >> blocksize, i_blocks). The i_blocks count is an upper limit, because it includes the overhead of indirect blocks. Directories cannot be sparse. Cheers, Andreas -- Andreas Dilger Principal Software Engineer Cluster File Systems, Inc. - To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
