Theodore Ts'o <tytso@xxxxxxx> writes: > Dimitry Monakhov discovered an edge case where it was possible for the > EXT4_EOFBLOCKS_FL flag could get cleared unnecessarily. This is true; > I have a test case that can be exercised via downloading and > decompressing the file: > > wget ftp://ftp.kernel.org/pub/linux/kernel/people/tytso/ext4-testcases/eofblocks-fl-test-case.img.bz2 > bunzip2 eofblocks-fl-test-case.img > dd if=/dev/zero of=eofblocks-fl-test-case.img bs=1k seek=17925 bs=1k count=1 conv=notrunc > > However, triggering it in real life is highly unlikely since it > requires an extremely fragmented sparse file with a hole in exactly > the right place in the extent tree. (It actually took quite a bit of This condition was triggered during fsstress test. So I consider it as rare but possible in real life. Nor than less it is better to fix it now, than fix it in response from a midnight call from some crazy customer :) > work to generate this test case.) Still, it's nice to get even > extreme corner cases to be correct, so this patch makes sure that we > don't clear the EXT4_EOFBLOCKS_FL incorrectly even in this corner > case. > > Signed-off-by: "Theodore Ts'o" <tytso@xxxxxxx> > --- > fs/ext4/extents.c | 18 +++++++++++++++--- > 1 files changed, 15 insertions(+), 3 deletions(-) > > diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c > index aeec5c7..c7c304f 100644 > --- a/fs/ext4/extents.c > +++ b/fs/ext4/extents.c > @@ -3319,7 +3319,7 @@ int ext4_ext_map_blocks(handle_t *handle, struct inode *inode, > struct ext4_extent_header *eh; > struct ext4_extent newex, *ex, *last_ex; > ext4_fsblk_t newblock; > - int err = 0, depth, ret, cache_type; > + int i, err = 0, depth, ret, cache_type; > unsigned int allocated = 0; > struct ext4_allocation_request ar; > ext4_io_end_t *io = EXT4_I(inode)->cur_aio_dio; > @@ -3508,8 +3508,20 @@ int ext4_ext_map_blocks(handle_t *handle, struct inode *inode, > goto out2; > } > last_ex = EXT_LAST_EXTENT(eh); > - if (map->m_lblk + ar.len > le32_to_cpu(last_ex->ee_block) > - + ext4_ext_get_actual_len(last_ex)) > + /* > + * If the current leaf block was reached by looking at > + * the last index block all the way down the tree, and > + * we are extending the inode beyond the last extent > + * in the current leaf block, then clear the > + * EOFBLOCKS_FL flag. > + */ > + for (i=depth-1; i >= 0; i--) { > + if (path[i].p_idx != EXT_LAST_INDEX(path[i].p_hdr)) > + break; This approach definitely looks better. > + } > + if ((i < 0) && > + (map->m_lblk + ar.len > le32_to_cpu(last_ex->ee_block) + > + ext4_ext_get_actual_len(last_ex))) > ext4_clear_inode_flag(inode, EXT4_INODE_EOFBLOCKS); > } > err = ext4_ext_insert_extent(handle, inode, path, &newex, flags); -- 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
