Re: [PATCH] fiemap: Allow to specify range to fiemap

Dave Chinner
2017-08-10T12:04:42Z

On Thu, Aug 10, 2017 at 02:07:44PM +0300, Nikolay Borisov wrote:
> Add 2 additional, optional, arguments to the embedded fiemap command,
> that way one can specify exact ranges to be fiemapped. This will be used
> for a btrfs test. Since the arguments are optional, omitting them just
> retains the old behavior.
>
> Signed-off-by: Nikolay Borisov <nborisov@suse.com>
> ---
> io/fiemap.c | 34 ++++++++++++++++++++++++++++++++--
> 1 file changed, 32 insertions(+), 2 deletions(-)
>
> diff --git a/io/fiemap.c b/io/fiemap.c
> index 75e8820..a3c0c89 100644
> --- a/io/fiemap.c
> +++ b/io/fiemap.c

Need to update the fiemap_help() text.

And a man page update.

> @@ -216,7 +216,11 @@ fiemap_f(
> int flg_w = 5;
> __u64 blocksize = 512;
> __u64 last_logical = 0;
> + __u64 len = -1LL;
> struct stat st;
> + size_t fsblocksize, fssectsize;
^

Whitespace damage.
> +
> + init_cvtnum(&fsblocksize, &fssectsize);
>
> while ((c = getopt(argc, argv, "aln:v")) != EOF) {
> switch (c) {
> @@ -237,6 +241,32 @@ fiemap_f(
> }
> }
>
> + if (argc == optind + 2) {
> + off64_t start_offset = cvtnum(fsblocksize, fssectsize, argv[optind]);
> + if (start_offset < 0) {
> + printf("non-numeric offset argument -- %s\n", argv[optind]);
> + return 0;
> + }
> + last_logical = start_offset;
> + last_logical = strtoull(argv[optind], NULL, 10);

Ah, what?

> +
> + optind++;
> +
> + off64_t length = cvtnum(fsblocksize, fssectsize, argv[optind]);
> + if (length < 0) {
> + printf("non-numeric len argument -- %s\n", argv[optind]);
> + return 0;
> + }
> + len = length;
> + } else if (argc == optind + 1) {
> + off64_t start_offset = cvtnum(fsblocksize, fssectsize, argv[optind]);
> + if (last_logical < 0) {
> + printf("non-numeric offset argument -- %s\n", argv[optind]);
> + return 0;
> + }
> + last_logical = start_offset;
> + }

Duplicate code to get start offset.

if (optind < argc) {
/* get start offset */
...
optind++
}
if (optind < argc) {
/* get length */
.....
}

Cheers,

Dave.
> +
> if (max_extents)
> num_extents = min(num_extents, max_extents);
> map_size = sizeof(struct fiemap) +
> @@ -259,7 +289,7 @@ fiemap_f(
> memset(fiemap, 0, map_size);
> fiemap->fm_flags = fiemap_flags;
> fiemap->fm_start = last_logical;
> - fiemap->fm_length = -1LL;
> + fiemap->fm_length = len;
> fiemap->fm_extent_count = num_extents;
>
> ret = ioctl(file->fd, FS_IOC_FIEMAP, (unsigned long)fiemap);
> @@ -350,7 +380,7 @@ fiemap_init(void)
> fiemap_cmd.argmin = 0;
> fiemap_cmd.argmax = -1;
> fiemap_cmd.flags = CMD_NOMAP_OK | CMD_FOREIGN_OK;
> - fiemap_cmd.args = _("[-alv] [-n nx]");
> + fiemap_cmd.args = _("[-alv] [-n nx] [start offset] [len]");

Given that it's {offset, len} or just {offset}, you can't have
length by itself as a parameter. i.e.

fiemap_cmd.args = _("[-alv] [-n nx] [start offset [len]]");

Cheers,

Dave.
--
Dave Chinner
david@fromorbit.com