Re: [PATCH 1/7] open_by_handle: store and load file handles from file

Eryu Guan
2018-01-11T11:59:06Z

On Sun, Jan 07, 2018 at 08:07:19PM +0200, Amir Goldstein wrote:
> usage:
> open_by_handle -p -o <handles_file> <test_dir> [N]
> open_by_handle -p -i <handles_file> <test_dir> [N]
>
> This will be used to test decoding of file handles after various
> file systems operations including mount cycle.
>
> Signed-off-by: Amir Goldstein <amir73il@gmail.com>

I found that it might be easier to review if the new test that takes use
of this new function is included in the same patch, so reviewer could
know how are these new functions being used without switching between
different patches.

> ---
> src/open_by_handle.c | 110 +++++++++++++++++++++++++++++++++++++++------------
> 1 file changed, 85 insertions(+), 25 deletions(-)
>
> diff --git a/src/open_by_handle.c b/src/open_by_handle.c
> index dbc5b0f..f9dfefc 100644
> --- a/src/open_by_handle.c
> +++ b/src/open_by_handle.c
> @@ -43,30 +43,36 @@ Examples:

The usage info above the "Examples:" can be updated too.

"usage: open_by_handle [-cludmrwapk] <test_dir> [num_files]"

>
> open_by_handle -p <test_dir> [N]
>
> -3. Get file handles for existing test set, write data to files,
> +3. Get file handles for existing test set and write them to a file.
> + Read file handles from file and open files by handle:
> +
> + open_by_handle -p -o <handles_file> <test_dir> [N]
> + open_by_handle -p -i <handles_file> <test_dir> [N]
> +
> +4. Get file handles for existing test set, write data to files,
> drop caches, open all files by handle, read and verify written
> data, write new data to file:
>
> open_by_handle -rwa <test_dir> [N]
>
> -4. Get file handles for existing test set, unlink all test files,
> +5. Get file handles for existing test set, unlink all test files,
> remove test_dir, drop caches, try to open all files by handle
> and expect ESTALE:
>
> open_by_handle -dp <test_dir> [N]
>
> -5. Get file handles for existing test set, keep open file handles for all
> +6. Get file handles for existing test set, keep open file handles for all
> test files, unlink all test files, drop caches and try to open all files
> by handle (should work):
>
> open_by_handle -dk <test_dir> [N]
>
> -6. Get file handles for existing test set, rename all test files,
> +7. Get file handles for existing test set, rename all test files,
> drop caches, try to open all files by handle (should work):
>
> open_by_handle -m <test_dir> [N]
>
> -7. Get file handles for existing test set, hardlink all test files,
> +8. Get file handles for existing test set, hardlink all test files,
> then unlink the original files, drop caches and try to open all
> files by handle (should work):
>
> @@ -103,7 +109,7 @@ struct handle {
>
> void usage(void)
> {
> - fprintf(stderr, "usage: open_by_handle [-cludmrwapk] <test_dir> [num_files]\n");
> + fprintf(stderr, "usage: open_by_handle [-cludmrwapk] [<-i|-o> <handles_file>] <test_dir> [num_files]\n");
> fprintf(stderr, "\n");
> fprintf(stderr, "open_by_handle -c <test_dir> [N] - create N test files under test_dir, try to get file handles and exit\n");
> fprintf(stderr, "open_by_handle <test_dir> [N] - get file handles of test files, drop caches and try to open by handle\n");
> @@ -116,6 +122,8 @@ void usage(void)
> fprintf(stderr, "open_by_handle -d <test_dir> [N] - unlink test files and hardlinks, drop caches and try to open by handle\n");
> fprintf(stderr, "open_by_handle -m <test_dir> [N] - rename test files, drop caches and try to open by handle\n");
> fprintf(stderr, "open_by_handle -p <test_dir> - create/delete and try to open by handle also test_dir itself\n");
> + fprintf(stderr, "open_by_handle -i <handles_file> <test_dir> [N] - read test files handles from file and try to open by handle\n");
> + fprintf(stderr, "open_by_handle -o <handles_file> <test_dir> [N] - get file handles of test files and write handles to file\n");
> exit(EXIT_FAILURE);
> }
>
> @@ -131,15 +139,16 @@ int main(int argc, char **argv)
> char *test_dir;
> char *mount_dir;
> int mount_fd, mount_id;
> + int in_fd = 0, out_fd = 0;
> int numfiles = 1;
> int create = 0, delete = 0, nlink = 1, move = 0;
> int rd = 0, wr = 0, wrafter = 0, parent = 0;
> int keepopen = 0;
>
> - if (argc < 2 || argc > 4)
> + if (argc < 2)
> usage();
>
> - while ((c = getopt(argc, argv, "cludmrwapk")) != -1) {
> + while ((c = getopt(argc, argv, "cludmrwapki:o:")) != -1) {
> switch (c) {
> case 'c':
> create = 1;
> @@ -176,13 +185,27 @@ int main(int argc, char **argv)
> case 'k':
> keepopen = 1;
> break;
> + case 'i':
> + in_fd = open(optarg, O_RDONLY);
> + if (in_fd < 0) {
> + perror(optarg);
> + return EXIT_FAILURE;
> + }
> + break;
> + case 'o':
> + out_fd = creat(optarg, 0644);
> + if (out_fd < 0) {
> + perror(optarg);
> + return EXIT_FAILURE;
> + }
> + break;
> default:
> fprintf(stderr, "illegal option '%s'\n", argv[optind]);
> case 'h':
> usage();
> }
> }
> - if (optind == argc || optind > 2)
> + if (optind == argc)
> usage();
> test_dir = argv[optind++];
> if (optind < argc)
> @@ -192,11 +215,14 @@ int main(int argc, char **argv)
> usage();
> }
>
> - if (parent) {
> + if (parent && !in_fd) {
> strcpy(dname, test_dir);
> /*
> * -p flag implies that test_dir is NOT a mount point,
> * so its parent can be used as mount_fd for open_by_handle_at.
> + * -i flag implies that test_dir IS a mount point, because we
> + * are testing open by handle of dir, which may have been
> + * deleted or renamed.

I'm a bit confused by this comment, is test_dir a mount point if I
specify both -i and -p? Does that mean -i would override -p regarding to
test_dir being mount point or not?

> */
> mount_dir = dirname(dname);
> if (create)
> @@ -241,15 +267,24 @@ int main(int argc, char **argv)
> /* sync to get the new inodes to hit the disk */
> sync();
>
> - /* create the handles */
> + /* create/read the handles */

This loop also write handles out, update the comment accordingly?

> 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);
> - if (ret < 0) {
> - strcat(fname, ": name_to_handle");
> - perror(fname);
> - return EXIT_FAILURE;
> + if (in_fd) {
> + ret = read(in_fd, (char *)&handle[i], sizeof(*handle));
> + if (ret < sizeof(*handle)) {
> + strcat(fname, ": read handle");
> + perror(fname);
> + return EXIT_FAILURE;
> + }
> + } else {
> + handle[i].fh.handle_bytes = MAX_HANDLE_SZ;
> + ret = name_to_handle_at(AT_FDCWD, fname, &handle[i].fh, &mount_id, 0);
> + if (ret < 0) {
> + strcat(fname, ": name_to_handle");
> + perror(fname);
> + return EXIT_FAILURE;
> + }
> }
> if (keepopen) {
> /* Open without close to keep unlinked files around */
> @@ -260,15 +295,40 @@ int main(int argc, char **argv)
> return EXIT_FAILURE;
> }
> }
> + if (out_fd) {
> + ret = write(out_fd, (char *)&handle[i], sizeof(*handle));
> + if (ret < sizeof(*handle)) {
> + strcat(fname, ": write handle");
> + perror(fname);

A short write is not an error, so errno is 0 and error message can be
confusing: "$file: write handle: Success"

> + return EXIT_FAILURE;
> + }
> + }
> }
>
> if (parent) {
> - dir_handle.fh.handle_bytes = MAX_HANDLE_SZ;
> - ret = name_to_handle_at(AT_FDCWD, test_dir, &dir_handle.fh, &mount_id, 0);
> - if (ret < 0) {
> - strcat(dname, ": name_to_handle");
> - perror(dname);
> - return EXIT_FAILURE;
> + if (in_fd) {
> + ret = read(in_fd, (char *)&dir_handle, sizeof(*handle));
> + if (ret < sizeof(*handle)) {

Same here, perror doesn't work with a short read.

> + strcat(dname, ": read handle");

With both -i and -p specified, dname is not initialized, then error
message is getting into:

: read handle: Success

> + perror(dname);
> + return EXIT_FAILURE;
> + }
> + } else {
> + dir_handle.fh.handle_bytes = MAX_HANDLE_SZ;
> + ret = name_to_handle_at(AT_FDCWD, test_dir, &dir_handle.fh, &mount_id, 0);
> + if (ret < 0) {
> + strcat(dname, ": name_to_handle");
> + perror(dname);
> + return EXIT_FAILURE;
> + }
> + }
> + if (out_fd) {
> + ret = write(out_fd, (char *)&dir_handle, sizeof(*handle));
> + if (ret < sizeof(*handle)) {
> + strcat(dname, ": write handle");
> + perror(dname);

Short write issue again.

Thanks,
Eryu

> + return EXIT_FAILURE;
> + }
> }
> }
>
> @@ -289,8 +349,8 @@ int main(int argc, char **argv)
> close(fd);
> }
>
> - /* after creating test set only check that fs supports exportfs */
> - if (create)
> + /* If creating test set or saving files handles, we are done */
> + if (create || out_fd)
> return EXIT_SUCCESS;
>
> /* hardlink the files */
> --
> 2.7.4
>