On Sun, Jul 20, 2008 at 11:08:25PM -0600, Andreas Dilger wrote: > On Jul 18, 2008 08:37 -0400, Theodore Ts'o wrote: > > On Fri, Jul 18, 2008 at 05:41:30PM +0530, Aneesh Kumar K.V wrote: > > > With fallocate FALLOC_FL_KEEP_SIZE option, when we write to prealloc > > > space and if we hit ENOSPC when trying to insert the extent, > > > we actually zero out the extent. That means we can have blocks > > > outside i_size for an inode. > > To clarify, doesn't FALLOC_FL_KEEP_SIZE put the extent beyond i_size, > regardless of whether the ENOSPC problem is hit? But the extent in that case would be marked as uninit using the extent len. So e2fsck can check for that. > > > > I guess e2fsck currently doesn't handle this. Or should we fix kernel > > > to update i_size to the right value if we do a zero out of the extent ? > > > > > > With fallocate if the prealloc area is small we also aggressively zeroout. > > > This was needed so that a random write pattern on falloc area doesn't > > > results in too many extents. That also can result in the above > > > error on fsck. > > > > It would seem to me that e2fsck should be fixed to not complain about > > blocks outside of i_size, *if* the blocks in question are marked as > > being unitialized. > > Yes, I think that is the right approach. That is fine for extents marked uninit. But when we zero out we zero out the full extent. So that means a write of few bytes can result in blocks being zeroed out outside i_size. My question was how e2fsck can handle this. Because the extent will no more be marked as uninit and there would be blocks outside i_size all carrying zero. > > > I suppose the other hack we could do is have e2fsck check the blocks > > that are outside of i_size, and if they are all zero and extents are > > involved, that it's a case of pre-allocated blocks that needed to be > > zero'ed for some reason, as opposed to a corrupted i_size. That seems > > to be a really gross hack, though. > > Yuck, with the added problem that there is no guarantee that these > data blocks ARE all zero. > -aneesh -- 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
