On 21.11.2017 18:02, Eric Sandeen wrote:
> 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.
>
> When the end of the requested region falls within an extent boundary then we
> print the whole extent (i.e. return all the information that the kernel has given
> us). When the end offset falls within a hole then the printed hole range is
> truncated to the requested one since we do not have information how long the
> hole is.
>
> Signed-off-by: Nikolay Borisov <nborisov@xxxxxxxx>
> [sandeen: simplify/rewrite ranged logic]
> Signed-off-by: Eric Sandeen <sandeen@xxxxxxxxxx>
>
> ---
> V6: <sandeen>
> * Update V5 changelog re: printed extents & end of range ;)
> * rename "last" to "done"
> * simplify loop control by setting done=1 in inner loop for all terminal conditions
> * update manpage re: behavior details for ranged queries
>
Reviewed-by: Nikolay Borisov <nborisov@xxxxxxxx>
> V5:
> * Now based on Eric's simpler approach.
> * Fix printed-extent counting in print_plain & print_verbose
> * Change while loop conditions to stop if full range has been mapped
>
> V4:
> * Don't do any fiemap processing if passed offset is past EOF. Filesystems
> might have custom handling for this. XFS for example pretends there is a
> hole.
>
> * Restore offset/len handling to using the optional params at the end of
> getopt and not using an additional '-r' param
>
> V3:
> * Fixed a bug where incorrect extent index was shown if we didn't print a
> hole. This was due to statically returning 2 at the end of print_(plain|verbose)
> Now, the actual number of printed extents inside the 2 functions is used.
> This bug is visible only with the -r parameter
>
> * Fixed a bug where 1 additional extent would be printed. This was a result of
> the aforementioned bug fix, since now printing function can return 1 and still
> have printed an extent and no hole. This can happen when you use -r parameter,
> this is now fixed and a comment explaining it is put.
>
> * Reworked the handling of the new params by making them arguments to the
> -r parameter.
>
> V2:
> * Incorporated Daricks feedback - removed variables which weren't introduced
> until the next patch as a result the build with this patch was broken. This is
> fixed now
>
> diff --git a/io/fiemap.c b/io/fiemap.c
> index bdcfacd..2f12652 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"));
> }
>
> @@ -101,6 +103,7 @@ print_verbose(
> char lbuf[48];
> char bbuf[48];
> char flgbuf[16];
> + int num_printed = 0;
>
> llast = BTOBBT(last_logical);
> lstart = BTOBBT(extent->fe_logical);
> @@ -118,14 +121,15 @@ 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++;
> + num_printed++;
> }
>
> if (cur_extent == max_extents)
> - return 1;
> + return num_printed;
>
> snprintf(lbuf, sizeof(lbuf), "[%llu..%llu]:",
> (unsigned long long)lstart, lstart + len - 1ULL);
> @@ -135,7 +139,9 @@ print_verbose(
> printf("%4d: %-*s %-*s %*llu %*s\n", cur_extent, foff_w, lbuf,
> boff_w, bbuf, tot_w, (unsigned long long)len, flg_w, flgbuf);
>
> - return 2;
> + num_printed++;
> +
> + return num_printed;
> }
>
> static int
> @@ -149,29 +155,33 @@ print_plain(
> __u64 llast;
> __u64 block;
> __u64 len;
> + int num_printed = 0;
>
> llast = BTOBBT(last_logical);
> lstart = BTOBBT(extent->fe_logical);
> 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++;
> + num_printed++;
> }
>
> if (cur_extent == max_extents)
> - return 1;
> + return num_printed;
>
> printf("\t%d: [%llu..%llu]: %llu..%llu", cur_extent,
> (unsigned long long)lstart, lstart + len - 1ULL,
> (unsigned long long)block, block + len - 1ULL);
>
> + num_printed++;
> +
> if (lflag)
> printf(_(" %llu blocks\n"), (unsigned long long)len);
> else
> printf("\n");
> - return 2;
> + return num_printed;
> }
>
> /*
> @@ -222,7 +232,7 @@ fiemap_f(
> char **argv)
> {
> struct fiemap *fiemap;
> - int last = 0;
> + int done = 0;
> int lflag = 0;
> int vflag = 0;
> int fiemap_flags = FIEMAP_FLAG_SYNC;
> @@ -235,9 +245,15 @@ 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 +273,27 @@ 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);
> @@ -269,12 +306,11 @@ fiemap_f(
>
> printf("%s:\n", file->name);
>
> - while (!last && (cur_extent != max_extents)) {
> -
> + while (!done) {
> 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);
> @@ -314,13 +350,23 @@ fiemap_f(
> cur_extent += num_printed;
> last_logical = extent->fe_logical + extent->fe_length;
>
> + /* Kernel has told us there are no more extents */
> if (extent->fe_flags & FIEMAP_EXTENT_LAST) {
> - last = 1;
> + done = 1;
> + break;
> + }
> +
> + /* We have exhausted the requested range */
> + if (last_logical >= range_end) {
> + done = 1;
> break;
> }
>
> - if (cur_extent == max_extents)
> + /* We have printed requested nr of extents */
> + if (cur_extent == max_extents) {
> + done = 1;
> break;
> + }
> }
> }
>
> @@ -336,9 +382,12 @@ 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 +402,7 @@ 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..fabf92f 100644
> --- a/man/man8/xfs_io.8
> +++ b/man/man8/xfs_io.8
> @@ -304,11 +304,23 @@ 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.
> +.PP
> +.RS
> +Optionally, this command also supports passing the start offset
> +from where to begin the mapping and the length of that region.
> +The kernel will return any full extents which intersect with the requested
> +range, and the
> +.B fiemap
> +command will print them in their entirety. If the requested range starts
> +or ends in a hole,
> +.B fiemap
> +will print the hole, truncated to the requested range.
> +.RE
> .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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