Re: [PATCH 2/4] src/open_by_handle: flexible usage options

Amir Goldstein
2017-04-19T09:57:51Z

On Wed, Apr 19, 2017 at 12:42 PM, Eryu Guan <eguan@redhat.com> wrote:
> On Tue, Apr 18, 2017 at 09:17:22PM +0300, Amir Goldstein wrote:
>> More usage options for testing open_by_handle, which are needed
>> for testing stable handles across copy up in overlayfs.
>>
>> usage: open_by_handle [-c|-l|-u|-d] <test_dir> [num_files]
>>
>> Examples:
>>
>> 1. Create N test files (nlink=1) under test_dir and exit:
>> $ open_by_handle -c <test_dir> [N]
>>
>> 2. Get file handles, drop caches and try to open by handle
>> (expects success):
>> $ open_by_handle <test_dir> [N]
>>
>> 3. Get file handles, create hardlinks to test files (nlink=2),
>> drop caches and try to open by handle (expects success):
>> $ open_by_handle -l <test_dir> [N]
>>
>> 4. Get file handles, unlink test files w/o the hardlinks (nlink=1),
>> drop caches and try to open by handle (expects success):
>> $ open_by_handle -u <test_dir> [N]
>>
>> 5. Get file handles, unlink test files and hardlinks (nlink=0),
>> drop caches and try to open by handle (expects failure):
>> $ open_by_handle -d <test_dir> [N]
>
> "The reason I separated -l (link) and -u (unlink) is because for
> overlayfs I need to test linking in lower layer and unlinking from
> overlay."
>
> I think it's better to have this in commit log too. (And more
> description of the usages of these options? I found that "-c" only
> creates test files not hard links, so a subsequent "-u" reports ESTALE,
> "-u" is only valid after a "-l". This could confuse testers, I guess.)
>

Certainly, this tool is dumb. It should be used in very specific ways.
I'll update the documentation with the sane use cases.

>>
>> Signed-off-by: Amir Goldstein <amir73il@gmail.com>
>> ---
>> src/open_by_handle.c | 93 ++++++++++++++++++++++++++++++++++++++++++++--------
>> 1 file changed, 80 insertions(+), 13 deletions(-)
>>
>> diff --git a/src/open_by_handle.c b/src/open_by_handle.c
>> index 8f04865..c33a4aa 100644
>> --- a/src/open_by_handle.c
>> +++ b/src/open_by_handle.c
>> @@ -37,12 +37,12 @@
>> #include <errno.h>
>> #include <linux/limits.h>
>>
>> -#define NUMFILES 1024
>> +#define MAXFILES 1024
>>
>> struct handle {
>> struct file_handle fh;
>> unsigned char fid[MAX_HANDLE_SZ];
>> -} handle[NUMFILES];
>> +} handle[MAXFILES];
>>
>> int main(int argc, char **argv)
>> {
>> @@ -51,18 +51,60 @@ int main(int argc, char **argv)
>> int ret;
>> int failed = 0;
>> char fname[PATH_MAX];
>> + char fname2[PATH_MAX];
>> char *test_dir;
>> int mount_fd, mount_id;
>> + int argi = 1, numfiles = 1;
>> + int create = 0, delete = 0, nlink = 1;
>>
>> - if (argc != 2) {
>> - fprintf(stderr, "usage: open_by_handle <test_dir>\n");
>> + if (argc < 2 || argc > 4) {
>> +usage:
>> + fprintf(stderr, "usage: open_by_handle [-c|-l|-u|-d] <test_dir> [num_files]\n");
>> + fprintf(stderr, "\n");
>> + fprintf(stderr, "open_by_handle -c <test_dir> [N] - create N test files under test_dir, get file handles and exit\n");
>> + fprintf(stderr, "open_by_handle <test_dir> [N] - get file handles, drop caches and try to open by handle (expects success)\n");
>> + fprintf(stderr, "open_by_handle -l <test_dir> [N] - get file handles, create hardlinks to test files (nlink=2), drop caches and try to open by handle (expects success)\n");
>> + fprintf(stderr, "open_by_handle -u <test_dir> [N] - get file handles, unlink test files w/o hardlinks (nlink=1), drop caches and try to open by handle (expects success)\n");
>> + fprintf(stderr, "open_by_handle -d <test_dir> [N] - get file handles, unlink test files and hardlinks (nlink=0), drop caches and try to open by handle (expects failure)\n");
>> return EXIT_FAILURE;
>> }
>>
>> - test_dir = argv[1];
>> + if (argv[1][0] == '-') {
>
> Hmm, why not "getopt"?
>

No reason, it started small with -c and grew into this. I guess getopt
is called for.

>> + if (argv[1][2])
>> + goto usage;
>> + switch (argv[1][1]) {
>> + case 'c':
>> + create = 1;
>> + break;
>> + case 'l':
>> + nlink = 2;
>> + break;
>> + case 'u':
>> + delete = 1;
>> + nlink = 1;
>> + break;
>> + case 'd':
>> + delete = 1;
>> + nlink = 0;
>> + break;
>> + default:
>> + fprintf(stderr, "illegal option '%s'\n", argv[1]);
>> + case 'h':
>> + goto usage;
>> + }
>> + argi++;
>> + }
>> + test_dir = argv[argi++];
>> + if (argc > argi)
>> + numfiles = atoi(argv[argi]);
>> + if (!numfiles || numfiles > MAXFILES) {
>> + fprintf(stderr, "illegal value '%s' for num_files\n", argv[argi]);
>> + goto usage;
>> + }
>> +
>> mount_fd = open(test_dir, O_RDONLY|O_DIRECTORY);
>> if (mount_fd < 0) {
>> - perror("open test_dir");
>> + perror(test_dir);
>> return EXIT_FAILURE;
>> }
>>
>> @@ -70,8 +112,9 @@ int main(int argc, char **argv)
>> * create a large number of files to force allocation of new inode
>> * chunks on disk.
>> */
>> - for (i=0; i < NUMFILES; i++) {
>> + for (i=0; create && i < numfiles; i++) {
>> sprintf(fname, "%s/file%06d", test_dir, i);
>> + sprintf(fname2, "%s/link%06d", test_dir, i);
>> fd = open(fname, O_RDWR | O_CREAT | O_TRUNC, 0644);
>> if (fd < 0) {
>> printf("Warning (%s,%d), open(%s) failed.\n", __FILE__, __LINE__, fname);
>> @@ -79,13 +122,14 @@ int main(int argc, char **argv)
>> return EXIT_FAILURE;
>> }
>> close(fd);
>> + ret = unlink(fname2);
>
> So "-c" also implies unlinking the hard links, mind updating the commit
> log and the comment above the for block?

Yes, it means create the test set, which implies blowing up previous
test leftovers.
I'll update the comments.

>
> But I'm not sure if it's a good idea for the test to depend on this
> subtle cleanup behavior, see my comments to patch #4.
>
>> }
>>
>> /* sync to get the new inodes to hit the disk */
>> sync();
>>
>> /* create the handles */
>> - for (i=0; i < NUMFILES; i++) {
>> + for (i=0; i < numfiles; i++) {
>> sprintf(fname, "%s/file%06d", test_dir, i);
>> handle[i].fh.handle_bytes = MAX_HANDLE_SZ;
>> ret = name_to_handle_at(AT_FDCWD, fname, &handle[i].fh, &mount_id, 0);
>> @@ -95,14 +139,32 @@ int main(int argc, char **argv)
>> }
>> }
>>
>> + /* after creating test set only check that fs supports exportfs */
>> + if (create)
>> + return EXIT_SUCCESS;
>
> "-c" means "Create N test files (nlink=1) under test_dir and exit", so
> we could move it before name_to_handle_at() calls?

That's the wording from commit message which is out of date.
usage says -c also tries to get handles, because it is being used for
_require_exportfs

>
>> +
>> + /* hardlink the files */
>> + for (i=0; nlink > 1 && i < numfiles; i++) {
>> + sprintf(fname, "%s/file%06d", test_dir, i);
>> + sprintf(fname2, "%s/link%06d", test_dir, i);
>> + ret = link(fname, fname2);
>> + if (ret < 0) {
>> + perror("link");
>> + return EXIT_FAILURE;
>> + }
>> + }
>> +
>> /* unlink the files */
>> - for (i=0; i < NUMFILES; i++) {
>> + for (i=0; delete && i < numfiles; i++) {
>> sprintf(fname, "%s/file%06d", test_dir, i);
>> + sprintf(fname2, "%s/link%06d", test_dir, i);
>> ret = unlink(fname);
>> if (ret < 0) {
>> perror("unlink");
>> return EXIT_FAILURE;
>> }
>> + if (!nlink)
>> + ret = unlink(fname2);
>
> I noticed that return values of unlink(fname2) are all ignored, is this
> intentional?
>

Yes. For -d it unlinks the hardlinks if they exist so jus unlink
and ignore the return value instead of stat+unlink.
worse a comment...

>> }
>>
>> /* sync to get log forced for unlink transactions to hit the disk */
>> @@ -126,17 +188,22 @@ int main(int argc, char **argv)
>> * now try to open the files by the stored handles. Expecting ENOENT
>> * for all of them.
>
> These comments should be updated too.
>

Right.
Thanks!

> Thanks,
> Eryu
>
>> */
>> - for (i=0; i < NUMFILES; i++) {
>> + for (i=0; i < numfiles; i++) {
>> errno = 0;
>> fd = open_by_handle_at(mount_fd, &handle[i].fh, O_RDWR);
>> - if (fd < 0 && (errno == ENOENT || errno == ESTALE)) {
>> + if (nlink && fd >= 0) {
>> + close(fd);
>> + continue;
>> + } else if (!nlink && fd < 0 && (errno == ENOENT || errno == ESTALE)) {
>> continue;
>> }
>> if (fd >= 0) {
>> printf("open_by_handle(%d) opened an unlinked file!\n", i);
>> close(fd);
>> - } else
>> - printf("open_by_handle(%d) returned %d incorrectly on an unlinked file!\n", i, errno);
>> + } else {
>> + printf("open_by_handle(%d) returned %d incorrectly on %s file!\n", i, errno,
>> + nlink ? "a linked" : "an unlinked");
>> + }
>> failed++;
>> }
>> if (failed)
>> --
>> 2.7.4
>>