On Fri, Nov 17, 2017 at 11:22:07AM -0600, Eric Sandeen wrote:
> From: Nikolay Borisov <nborisov@xxxxxxxx>
>
> Currently the fiemap implementation of xfs_io doesn't support making ranged
> queries. This patch implements two optional arguments which take the starting
> offset and the length of the region to be queried.
>
> Signed-off-by: Nikolay Borisov <nborisov@xxxxxxxx>
> [sandeen: simplify/rewrite ranged logic]
> Signed-off-by: Eric Sandeen <sandeen@xxxxxxxxxx>
>
Reviewed-by: Bill O'Donnell <billodo@xxxxxxxxxx>
> ---
>
> I think this is a simpler approach. There are some questions about how
> the fiemap command should handle holes and ranges, however.
>
> First and foremost, the kernel will return any extent(s) which overlap(s)
> with the requested range. Holes are simply inferred by xfs_io from the
> spaces in between.
>
> So there are questions about what to do if i.e. the range starts or ends
> in a hole.
>
> This patch (I think!) /will/ describe a hole on either side of the requested
> range, if it exists, with start and end points of the hole(s) based on
> the range start & end. i.e. with range on boundaries:
>
> # io/xfs_io -c "fiemap 0 12k" alternating
> alternating:
> 0: [0..7]: hole
> 1: [8..15]: 60550776..60550783
> 2: [16..23]: hole
>
> with range in middle of holes, hole ranges are truncated:
>
> # io/xfs_io -c "fiemap 1k 10k" alternating
> alternating:
> 0: [2..7]: hole
> 1: [8..15]: 60550776..60550783
> 2: [16..21]: hole
>
> i.e. note that the first hole starts at the requested 1k range, and
> the last hole ends at the end of the requested range.
>
> Seems reasonable?
>
>
>
> diff --git a/io/fiemap.c b/io/fiemap.c
> index bdcfacd..266d134 100644
> --- a/io/fiemap.c
> +++ b/io/fiemap.c
> @@ -49,6 +49,8 @@ fiemap_help(void)
> " -l -- also displays the length of each extent in 512-byte blocks.\n"
> " -n -- query n extents.\n"
> " -v -- Verbose information\n"
> +" offset is the starting offset to map, and is optional. If offset is\n"
> +" specified, mapping length may (optionally) be specified as well."
> "\n"));
> }
>
> @@ -118,7 +120,7 @@ print_verbose(
> flg_w, _("FLAGS"));
> }
>
> - if (lstart != llast) {
> + if (lstart > llast) {
> print_hole(foff_w, boff_w, tot_w, cur_extent, 0, false, llast,
> lstart);
> cur_extent++;
> @@ -155,7 +157,7 @@ print_plain(
> len = BTOBBT(extent->fe_length);
> block = BTOBBT(extent->fe_physical);
>
> - if (lstart != llast) {
> + if (lstart > llast) {
> print_hole(0, 0, 0, cur_extent, lflag, true, llast, lstart);
> cur_extent++;
> }
> @@ -235,9 +237,15 @@ fiemap_f(
> int boff_w = 16;
> int tot_w = 5; /* 5 since its just one number */
> int flg_w = 5;
> - __u64 last_logical = 0;
> + __u64 last_logical = 0; /* last extent offset handled */
> + off64_t start_offset = 0; /* mapping start */
> + off64_t length = -1LL; /* mapping length */
> + off64_t range_end = -1LL; /* mapping end*/
> + size_t fsblocksize, fssectsize;
> struct stat st;
>
> + init_cvtnum(&fsblocksize, &fssectsize);
> +
> while ((c = getopt(argc, argv, "aln:v")) != EOF) {
> switch (c) {
> case 'a':
> @@ -257,6 +265,27 @@ fiemap_f(
> }
> }
>
> + /* Range start (optional) */
> + if (optind < argc) {
> + 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;
> + optind++;
> + }
> +
> + /* Range length (optional if range start was specified) */
> + if (optind < argc) {
> + length = cvtnum(fsblocksize, fssectsize, argv[optind]);
> + if (length < 0) {
> + printf("non-numeric len argument -- %s\n", argv[optind]);
> + return 0;
> + }
> + range_end = start_offset + length;
> + }
> +
> map_size = sizeof(struct fiemap) +
> (EXTENT_BATCH * sizeof(struct fiemap_extent));
> fiemap = malloc(map_size);
> @@ -274,7 +303,7 @@ fiemap_f(
> memset(fiemap, 0, map_size);
> fiemap->fm_flags = fiemap_flags;
> fiemap->fm_start = last_logical;
> - fiemap->fm_length = -1LL;
> + fiemap->fm_length = range_end - last_logical;
> fiemap->fm_extent_count = EXTENT_BATCH;
>
> ret = ioctl(file->fd, FS_IOC_FIEMAP, (unsigned long)fiemap);
> @@ -336,9 +365,12 @@ fiemap_f(
> return 0;
> }
>
> - if (cur_extent && last_logical < st.st_size)
> + /* Print last hole to EOF or to end of requested range */
> + range_end = min((uint64_t)range_end, st.st_size);
> +
> + if (cur_extent && last_logical < range_end)
> print_hole(foff_w, boff_w, tot_w, cur_extent, lflag, !vflag,
> - BTOBBT(last_logical), BTOBBT(st.st_size));
> + BTOBBT(last_logical), BTOBBT(range_end));
>
> out:
> free(fiemap);
> @@ -353,7 +385,7 @@ 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] [offset [len]]");
> fiemap_cmd.oneline = _("print block mapping for a file");
> fiemap_cmd.help = fiemap_help;
>
> diff --git a/man/man8/xfs_io.8 b/man/man8/xfs_io.8
> index 9bf1a47..7633734 100644
> --- a/man/man8/xfs_io.8
> +++ b/man/man8/xfs_io.8
> @@ -304,11 +304,12 @@ Prints the block mapping for the current open file. Refer to the
> .BR xfs_bmap (8)
> manual page for complete documentation.
> .TP
> -.BI "fiemap [ \-alv ] [ \-n " nx " ]"
> +.BI "fiemap [ \-alv ] [ \-n " nx " ] [ " offset " [ " len " ]]"
> Prints the block mapping for the current open file using the fiemap
> ioctl. Options behave as described in the
> .BR xfs_bmap (8)
> -manual page.
> +manual page. Optionally, this command also supports passing the start offset
> +from where to begin the fiemap and the length of that region.
> .TP
> .BI "fsmap [ \-d | \-l | \-r ] [ \-m | \-v ] [ \-n " nx " ] [ " start " ] [ " end " ]
> Prints the mapping of disk blocks used by the filesystem hosting the current
>
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