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Date: Sun, 22 May 2011 20:38:27 +0800
From: Yongqiang Yang <xiaoqiangnk@...il.com>
To: Dave Chinner <david@...morbit.com>
Cc: josef@...hat.com, sandeen@...hat.com, xfs@....sgi.com,
linux-ext4@...r.kernel.org
Subject: Re: [PATCH v2] xfstests:Make 225 compare map and fiemap at each block.
Hi Dave,
Thank you for your review. I will resend it.
On Thu, May 19, 2011 at 7:12 PM, Dave Chinner <david@...morbit.com> wrote:
> On Thu, May 19, 2011 at 03:21:05PM +0800, Yongqiang Yang wrote:
>> Due to my carelessness, I induced a ugly patch to ext4's fiemap, but
>> 225 could not find it. So I looked into the 225 and could not figure out
>> logic in compare_map_and_fiemap(), which seemed to mix extents with
>> blocks. Then I made 225 compare map and fiemap at each block, the new
>> 225 can find another bug in ext4 with 1k block.
>>
>> The new 225 works well on ext3, ext4 and xfs with both 1K and 4K block.
>
> The change log could do with some work. What cases did 225 not
> cover, what new cases does it cover, what are the impacts of the
> change, what bugs were fixed, etc. "I didn't understand the existing
> code so I rewrote it" isn't very useful to someone trying to
> understand why the changes were made in a couple of years time....
>
>>
>> Signed-off-by: Yongqiang Yang <xiaoqiangnk@...il.com>
>> ---
>> v1->v2:
>> Josef <josef@...hat.com> reviewed the v1 patch and pointed out the bug which
>> made xfs not work and several coding styles.
>>
>> According to reply from Josef, I
>> fixed the bug which added ';' after an if statement.
>> removed the trailing whitespace.
>>
>> Apart from things above, I
>> made check_weird_fs_hole() verify bytes read by pread().
>>
>> src/fiemap-tester.c | 251 ++++++++++++++++++++++++++++-----------------------
>> 1 files changed, 140 insertions(+), 111 deletions(-)
>>
>> diff --git a/src/fiemap-tester.c b/src/fiemap-tester.c
>> index 1663f84..319a9bb 100644
>> --- a/src/fiemap-tester.c
>> +++ b/src/fiemap-tester.c
>> @@ -14,6 +14,9 @@
>> * You should have received a copy of the GNU General Public License
>> * along with this program; if not, write the Free Software Foundation,
>> * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
>> + *
>> + * Compare map and fiemap at each block,
>> + * Yongqiang Yang <xiaoqiangnk@...il.com>, 2011
>> */
>
> Changelogs belong in the repository commit message, not the code.
>
>> #include <stdio.h>
>> @@ -57,7 +60,7 @@ generate_file_mapping(int blocks, int prealloc)
>> int num_types = 2, cur_block = 0;
>> int i = 0;
>>
>> - map = malloc(sizeof(char) * blocks);
>> + map = malloc(sizeof(char) * (blocks + 1));
>
> What is the bug this is fixing? Nothing in the change log tells me
> why this is being done....
>
>> if (!map)
>> return NULL;
>>
>> @@ -81,6 +84,7 @@ generate_file_mapping(int blocks, int prealloc)
>> cur_block++;
>> }
>>
>> + map[blocks] = 0;
>
> Why is this necessary?
If there are any errors, map is printed out as a string.
>
>> return map;
>> }
>>
>> @@ -247,55 +251,36 @@ check_flags(struct fiemap *fiemap, int blocksize)
>> }
>>
>> static int
>> -check_data(struct fiemap *fiemap, __u64 logical_offset, int blocksize,
>> +check_data(struct fiemap_extent *extent , __u64 logical_offset, int blocksize,
>> int last, int prealloc)
>
> Perhaps adding a comment explaing what the function is actually
> checking is in order seeing as you just changed it...
>
> ....
>> @@ -306,7 +291,7 @@ static int
>> check_weird_fs_hole(int fd, __u64 logical_offset, int blocksize)
>> {
>> static int warning_printed = 0;
>> - int block, i;
>> + int block, i, count;
>> size_t buf_len = sizeof(char) * blocksize;
>> char *buf;
>>
>> @@ -330,15 +315,16 @@ check_weird_fs_hole(int fd, __u64 logical_offset, int blocksize)
>> return -1;
>> }
>>
>> - if (pread(fd, buf, buf_len, (off_t)logical_offset) < 0) {
>> + count = pread(fd, buf, buf_len, (off_t)logical_offset);
>> + if (count < 0) {
>> perror("Error reading from file");
>> free(buf);
>> return -1;
>> }
>>
>> - for (i = 0; i < buf_len; i++) {
>> + for (i = 0; i < count; i++) {
>
> What bug in the test is this fixing? Surely a short read indicates
> a filesystem problem? Only checking the bytes returned instead of
> the entire hole region will hide the fact that the read didn't cover
> the range that was asked for and so we haven't validated the entire
> region we were supposed to...
I think read operation is verified in other tests, XFS has blocks
after the size, so I rely on read bytes.
>
>> @@ -370,35 +356,25 @@ check_weird_fs_hole(int fd, __u64 logical_offset, int blocksize)
>> }
>>
>> static int
>> -check_hole(struct fiemap *fiemap, int fd, __u64 logical_offset, int blocksize)
>> +check_hole(struct fiemap_extent *extent, int fd, __u64 logical_offset,
>> + int blocksize)
>> {
>
> Same issue with adding a comment explaining what is being
> checked....
>
>> - struct fiemap_extent *extent;
>> - int c;
>> + __u64 start, end;
>>
>> - for (c = 0; c < fiemap->fm_mapped_extents; c++) {
>> - __u64 start, end;
>> - extent = &fiemap->fm_extents[c];
>> -
>> - start = extent->fe_logical;
>> - end = extent->fe_logical + extent->fe_length;
>> -
>> - if (logical_offset > end)
>> - continue;
>> - if (logical_offset + blocksize < start)
>> - break;
>> + start = extent->fe_logical;
>> + end = extent->fe_logical + extent->fe_length;
>>
>> - if (logical_offset >= start &&
>> - logical_offset < end) {
>> + if (logical_offset >= start &&
>> + logical_offset < end) {
>>
>> - if (check_weird_fs_hole(fd, logical_offset,
>> - blocksize) == 0)
>> - break;
>> + if (check_weird_fs_hole(fd, logical_offset,
>> + blocksize) == 0)
>> + return 0;
>
> error = check_weird_fs_hole(fd, logical_offset,
> blocksize);
> if (error == 0)
> return 0;
>
>> @@ -423,9 +399,11 @@ compare_fiemap_and_map(int fd, char *map, int blocks, int blocksize, int syncfil
>> {
>> struct fiemap *fiemap;
>> char *fiebuf;
>> - int blocks_to_map, ret, cur_extent = 0, last_data;
>> + int blocks_to_map, ret, last_data = -1;
>> __u64 map_start, map_length;
>> int i, c;
>> + int cur_block = 0;
>> + int last_found = 0;
>>
>> if (query_fiemap_count(fd, blocks, blocksize) < 0)
>> return -1;
>> @@ -451,8 +429,11 @@ compare_fiemap_and_map(int fd, char *map, int blocks, int blocksize, int syncfil
>> fiemap->fm_extent_count = blocks_to_map;
>> fiemap->fm_mapped_extents = 0;
>>
>> + /* check fiemap by looking at each block. */
>> do {
>> - fiemap->fm_start = map_start;
>> + int nr_extents;
>> +
>> + fiemap->fm_start = cur_block * blocksize;
>> fiemap->fm_length = map_length;
>>
>> ret = ioctl(fd, FS_IOC_FIEMAP, (unsigned long)fiemap);
>> @@ -465,45 +446,93 @@ compare_fiemap_and_map(int fd, char *map, int blocks, int blocksize, int syncfil
>> if (check_flags(fiemap, blocksize))
>> goto error;
>>
>> - for (i = cur_extent, c = 1; i < blocks; i++, c++) {
>> - __u64 logical_offset = i * blocksize;
>> -
>> - if (c > fiemap->fm_mapped_extents) {
>> - i++;
>> - break;
>> + nr_extents = fiemap->fm_mapped_extents;
>> + if (nr_extents == 0) {
>> + int block = cur_block + (map_length - 1) / blocksize;
>> + for (; cur_block <= block &&
>> + cur_block < blocks; cur_block++) {
>> + /* check hole */
>> + if (map[cur_block] != 'H') {
>> + printf("ERROR: map[%d] should not be "
>> + "a hole\n", cur_block);
>> + goto error;
>> + }
>> }
>> + continue;
>> + }
>>
>> - switch (map[i]) {
>> - case 'D':
>> - if (check_data(fiemap, logical_offset,
>> - blocksize, last_data == i, 0))
>> + for (c = 0; c < nr_extents; c++) {
>> + __u64 offset;
>> + int block;
>> + struct fiemap_extent *extent;
>> +
>> +
>> + extent = &fiemap->fm_extents[c];
>> + offset = extent->fe_logical;
>> + block = offset / blocksize;
>> +
>> + /* check hole. */
>> + for (; cur_block < block && cur_block < blocks;
>> + cur_block++) {
>> + if (map[cur_block] != 'H') {
>> + printf("ERROR: map[%d] should not be "
>> + "a hole\n", cur_block);
>> goto error;
>> - break;
>> - case 'H':
>> - if (check_hole(fiemap, fd, logical_offset,
>> - blocksize))
>> + }
>> + }
>> +
>> + offset = extent->fe_logical + extent->fe_length;
>> + block = offset / blocksize;
>> + /* check data */
>> + for (; cur_block < block && cur_block < blocks;
>> + cur_block++) {
>> + int last;
>> + offset = (__u64)cur_block * blocksize;
>> + last = (cur_block == last_data);
>> + last_found = last_found ? last_found : last;
>> + switch (map[cur_block]) {
>> + case 'D':
>> + if (check_data(extent, offset,
>> + blocksize, last, 0))
>> + goto error;
>> + break;
>> + case 'H':
>> + if (check_hole(extent, fd, offset,
>> + blocksize))
>> + goto error;
>> + break;
>> +
>> + case 'P':
>> + if (check_data(extent, offset,
>> + blocksize, last, 1))
>> + goto error;
>> + break;
>> + default:
>> + printf("ERROR: weird value in "
>> + "map: %c\n", map[i]);
>> goto error;
>> - break;
>> - case 'P':
>> - if (check_data(fiemap, logical_offset,
>> - blocksize, last_data == i, 1))
>> + }
>> + }
>> +
>> + for (; cur_block < block; cur_block++) {
>> + offset = (__u64)cur_block * blocksize;
>> + if (check_hole(extent, fd, offset, blocksize))
>> goto error;
>> - break;
>> - default:
>> - printf("ERROR: weird value in map: %c\n",
>> - map[i]);
>> - goto error;
>> }
>> }
>> - cur_extent = i;
>> - map_start = i * blocksize;
>> - } while (cur_extent < blocks);
>> + } while (cur_block < blocks);
>>
>> - ret = 0;
>> - return ret;
>> + if (!last_found && last_data != -1) {
>> + printf("ERROR: find no last extent\n");
>> + goto error;
>> + }
>> +
>> + free(fiebuf);
>> + return 0;
>> error:
>> printf("map is '%s'\n", map);
>> show_extents(fiemap, blocksize);
>> + free(fiebuf);
>> return -1;
>> }
>
> I can't say I like this - the previous way of iterating the map and
> checking that the overlapping fiemap extent is of the correct type
> seems much simpler to me.
>
> Your code now has to special case fiemaps with nr_extents == 0, has
> to handle holes separately both before and after data extents and
> adds a bunch of duplicated code. I find it much harder to follow,
> and I don't see how rewriting the code like this makes the test
> better. Especially as it doesn't tell me what the problems with the
> original code were that you've supposedly fixed...
I could not figure out logic in old code comparing fiemap and map,
I will update the changelog.
>
>>
>> @@ -605,6 +634,18 @@ main(int argc, char **argv)
>> printf("Starting infinite run, if you don't see any output "
>> "then its working properly.\n");
>> do {
>> + if (ftruncate(fd, 0)) {
>> + perror("Could not truncate file\n");
>> + close(fd);
>> + exit(1);
>> + }
>> +
>> + if (lseek(fd, 0, SEEK_SET)) {
>> + perror("Could not seek set\n");
>> + close(fd);
>> + exit(1);
>> + }
>> +
>> if (!map) {
>> blocks = random() % maxblocks;
>> if (blocks == 0) {
>> @@ -639,18 +680,6 @@ main(int argc, char **argv)
>> free(map);
>> map = NULL;
>>
>> - if (ftruncate(fd, 0)) {
>> - perror("Could not truncate file\n");
>> - close(fd);
>> - exit(1);
>> - }
>> -
>> - if (lseek(fd, 0, SEEK_SET)) {
>> - perror("Could not seek set\n");
>> - close(fd);
>> - exit(1);
>> - }
>> -
>> if (runs) runs--;
>> } while (runs != 0);
>
> What bug is this fixing? There's Nothing in the changelog....
>
> Cheers,
>
> Dave.
> --
> Dave Chinner
> david@...morbit.com
>
--
Best Wishes
Yongqiang Yang
--
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