On 11.08.2017 14:55, Nikolay Borisov wrote:
> fiemap's code was rather complicated for the simple task it did so this
> patch aims to rectify the situation. The main changes are:
>
> * Add a start_offset, len parameters, this allows to specify a range of the
> file for which we want information, if those parameters are omitted the old
> behavior is retained i.e. we get information for the whole file.
>
> * We now always allocate as many struct fiemap_extent structs as necessary
> to hold the information for the passed range (or the whole file)
>
> * Made max_extents, blocksize global variables. They are never modified apart
> from the initilization of the program.
>
> * Eliminated the outer while loop, now that we allocate enough extent to
> perform a single fiemap ioctl call there is no need for it.
>
> * As a result the -n parameter works correctly for -n 1
>
> * Also changed the way the last hole is being calculated, so far every time
> the outter while loop finished the extenet from last_logical .. file size would
> be output as a hole. This was not always true
>
> Signed-off-by: Nikolay Borisov <nborisov@xxxxxxxx>
> ---
>
> Hello,
>
> Here is more or less a major cleanup of the fiemap code. I've tested it with a
> file with with the following layout HDHDHDHDHDHD (H - hole, D-data) and
> varying permutation of the arguments and so far everthing seems to work as
> expected. The biggest benefit I see is that the code is easier to follow now.
Ping
>
>
> io/fiemap.c | 187 +++++++++++++++++++++++++++++-------------------------
> man/man8/xfs_io.8 | 5 +-
> 2 files changed, 104 insertions(+), 88 deletions(-)
>
> diff --git a/io/fiemap.c b/io/fiemap.c
> index 75e882057362..5659f16d767d 100644
> --- a/io/fiemap.c
> +++ b/io/fiemap.c
> @@ -24,6 +24,8 @@
> #include "io.h"
>
> static cmdinfo_t fiemap_cmd;
> +static const __u64 blocksize = 512;
> +static int max_extents = 0;
>
> static void
> fiemap_help(void)
> @@ -34,6 +36,7 @@ fiemap_help(void)
> "\n"
> " Example:\n"
> " 'fiemap -v' - tabular format verbose map\n"
> +" 'fiemap 0 4k' - print fiemap extents for 0-4k range\n"
> "\n"
> " fiemap prints the map of disk blocks used by the current file.\n"
> " The map lists each extent used by the file, as well as regions in the\n"
> @@ -52,12 +55,10 @@ fiemap_help(void)
> static void
> print_verbose(
> struct fiemap_extent *extent,
> - int blocksize,
> int foff_w,
> int boff_w,
> int tot_w,
> int flg_w,
> - int max_extents,
> int *cur_extent,
> __u64 *last_logical)
> {
> @@ -85,6 +86,7 @@ print_verbose(
> flg_w, _("FLAGS"));
> }
>
> +
> if (lstart != llast) {
> snprintf(lbuf, sizeof(lbuf), "[%llu..%llu]:", llast,
> lstart - 1ULL);
> @@ -94,7 +96,7 @@ print_verbose(
> memset(lbuf, 0, sizeof(lbuf));
> }
>
> - if ((*cur_extent + 1) == max_extents)
> + if (max_extents && *cur_extent == max_extents)
> return;
>
> snprintf(lbuf, sizeof(lbuf), "[%llu..%llu]:", lstart,
> @@ -112,8 +114,6 @@ static void
> print_plain(
> struct fiemap_extent *extent,
> int lflag,
> - int blocksize,
> - int max_extents,
> int *cur_extent,
> __u64 *last_logical)
> {
> @@ -137,7 +137,7 @@ print_plain(
> (*cur_extent)++;
> }
>
> - if ((*cur_extent + 1) == max_extents)
> + if (max_extents && *cur_extent == max_extents)
> return;
>
> printf("\t%d: [%llu..%llu]: %llu..%llu", *cur_extent,
> @@ -159,13 +159,12 @@ print_plain(
> static void
> calc_print_format(
> struct fiemap *fiemap,
> - __u64 blocksize,
> int *foff_w,
> int *boff_w,
> int *tot_w,
> int *flg_w)
> {
> - int i;
> + int i;
> char lbuf[32];
> char bbuf[32];
> __u64 logical;
> @@ -193,15 +192,28 @@ calc_print_format(
> }
> }
>
> +static ssize_t
> +get_extent_num(int fd, __u64 startoffset, __u64 len)
> +{
> + struct fiemap fiemap = { 0 } ;
> + fiemap.fm_start = startoffset;
> + fiemap.fm_length = len;
> + if (ioctl(fd, FS_IOC_FIEMAP, (unsigned long)&fiemap) < 0) {
> + fprintf(stderr, _("%s: Failed to query fiemap extent count.\n"),
> + progname);
> + return -1;
> + }
> +
> + return fiemap.fm_mapped_extents;
> +}
> +
> int
> fiemap_f(
> int argc,
> char **argv)
> {
> struct fiemap *fiemap;
> - int max_extents = 0;
> - int num_extents = 32;
> - int last = 0;
> + int num_extents;
> int lflag = 0;
> int vflag = 0;
> int fiemap_flags = FIEMAP_FLAG_SYNC;
> @@ -210,24 +222,29 @@ fiemap_f(
> int map_size;
> int ret;
> int cur_extent = 0;
> - int foff_w = 16; /* 16 just for a good minimum range */
> + int foff_w = 16; /* 16 just for a good minimum range */
> int boff_w = 16;
> int tot_w = 5; /* 5 since its just one number */
> int flg_w = 5;
> - __u64 blocksize = 512;
> __u64 last_logical = 0;
> - struct stat st;
> + __u64 len = -1LL;
> + size_t fsblocksize, fssectsize;
> + off64_t start_offset = 0;
> + __u64 end_offset;
> + __u64 llast;
> + bool last_extent = false;
> +
> + init_cvtnum(&fsblocksize, &fssectsize);
>
> while ((c = getopt(argc, argv, "aln:v")) != EOF) {
> switch (c) {
> case 'a':
> fiemap_flags |= FIEMAP_FLAG_XATTR;
> break;
> - case 'l':
> - lflag = 1;
> - break;
> case 'n':
> max_extents = atoi(optarg);
> + case 'l':
> + lflag = 1;
> break;
> case 'v':
> vflag++;
> @@ -237,8 +254,35 @@ fiemap_f(
> }
> }
>
> - if (max_extents)
> - num_extents = min(num_extents, max_extents);
> + 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++;
> + }
> +
> + if (optind < argc) {
> + off64_t length = cvtnum(fsblocksize, fssectsize, argv[optind]);
> + if (length < 0) {
> + printf("non-numeric len argument -- %s\n", argv[optind]);
> + return 0;
> + }
> + len = length;
> + }
> +
> +
> + end_offset = (start_offset + len) / blocksize;
> +
> + ret = get_extent_num(file->fd, last_logical, len);
> + if (ret < 0) {
> + exitcode = 1;
> + return 0;
> + }
> + num_extents = ret;
> +
> map_size = sizeof(struct fiemap) +
> (num_extents * sizeof(struct fiemap_extent));
> fiemap = malloc(map_size);
> @@ -251,92 +295,63 @@ fiemap_f(
>
> printf("%s:\n", file->name);
>
> - while (!last && ((cur_extent + 1) != max_extents)) {
> - if (max_extents)
> - num_extents = min(num_extents,
> - max_extents - (cur_extent + 1));
> -
> - memset(fiemap, 0, map_size);
> - fiemap->fm_flags = fiemap_flags;
> - fiemap->fm_start = last_logical;
> - fiemap->fm_length = -1LL;
> - fiemap->fm_extent_count = num_extents;
> -
> - ret = ioctl(file->fd, FS_IOC_FIEMAP, (unsigned long)fiemap);
> - if (ret < 0) {
> - fprintf(stderr, "%s: ioctl(FS_IOC_FIEMAP) [\"%s\"]: "
> - "%s\n", progname, file->name, strerror(errno));
> - free(fiemap);
> - exitcode = 1;
> - return 0;
> - }
> + memset(fiemap, 0, map_size);
> + fiemap->fm_flags = fiemap_flags;
> + fiemap->fm_start = last_logical;
> + fiemap->fm_length = len;
> + fiemap->fm_extent_count = num_extents;
>
> - /* No more extents to map, exit */
> - if (!fiemap->fm_mapped_extents)
> - break;
> + ret = ioctl(file->fd, FS_IOC_FIEMAP, (unsigned long)fiemap);
> + if (ret < 0) {
> + fprintf(stderr, "%s: ioctl(FS_IOC_FIEMAP) [\"%s\"]: "
> + "%s\n", progname, file->name, strerror(errno));
> + free(fiemap);
> + exitcode = 1;
> + return 0;
> + }
> +
> + for (i = 0; i < fiemap->fm_mapped_extents; i++) {
> + struct fiemap_extent *extent;
>
> - for (i = 0; i < fiemap->fm_mapped_extents; i++) {
> - struct fiemap_extent *extent;
> -
> - extent = &fiemap->fm_extents[i];
> - if (vflag) {
> - if (cur_extent == 0) {
> - calc_print_format(fiemap, blocksize,
> - &foff_w, &boff_w,
> - &tot_w, &flg_w);
> - }
> -
> - print_verbose(extent, blocksize, foff_w,
> - boff_w, tot_w, flg_w,
> - max_extents, &cur_extent,
> - &last_logical);
> - } else
> - print_plain(extent, lflag, blocksize,
> - max_extents, &cur_extent,
> - &last_logical);
> -
> - if (extent->fe_flags & FIEMAP_EXTENT_LAST) {
> - last = 1;
> - break;
> + extent = &fiemap->fm_extents[i];
> + if (vflag) {
> + if (cur_extent == 0) {
> + calc_print_format(fiemap, &foff_w, &boff_w,
> + &tot_w, &flg_w);
> }
>
> - if ((cur_extent + 1) == max_extents)
> - break;
> - }
> - }
> + print_verbose(extent, foff_w, boff_w, tot_w, flg_w,
> + &cur_extent, &last_logical);
> + } else
> + print_plain(extent, lflag, &cur_extent, &last_logical);
>
> - if ((cur_extent + 1) == max_extents)
> - goto out;
> + if (max_extents && cur_extent == max_extents)
> + goto out;
> +
> + if (extent->fe_flags & FIEMAP_EXTENT_LAST)
> + last_extent = true;
>
> - memset(&st, 0, sizeof(st));
> - if (fstat(file->fd, &st)) {
> - fprintf(stderr, "%s: fstat failed: %s\n", progname,
> - strerror(errno));
> - free(fiemap);
> - exitcode = 1;
> - return 0;
> }
>
> - if (cur_extent && last_logical < st.st_size) {
> - char lbuf[32];
> + llast = last_logical / blocksize;
> + if (!last_extent && llast < end_offset) {
> + char lbuf[32];
> + __u64 difference = end_offset - llast;
> + snprintf(lbuf, sizeof(lbuf), "[%llu..%llu]:", llast, llast + difference);
>
> - snprintf(lbuf, sizeof(lbuf), "[%llu..%llu]:",
> - last_logical / blocksize, (st.st_size / blocksize) - 1);
> if (vflag) {
> printf("%4d: %-*s %-*s %*llu\n", cur_extent,
> foff_w, lbuf, boff_w, _("hole"), tot_w,
> - (st.st_size - last_logical) / blocksize);
> + difference);
> } else {
> printf("\t%d: %s %s", cur_extent, lbuf,
> _("hole"));
> if (lflag)
> - printf(_(" %llu blocks\n"),
> - (st.st_size - last_logical) / blocksize);
> + printf(_(" %llu blocks\n"), len / blocksize);
> else
> printf("\n");
> }
> }
> -
> out:
> free(fiemap);
> return 0;
> @@ -350,7 +365,7 @@ 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]]");
> 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 273b9c54c52d..125db9181851 100644
> --- a/man/man8/xfs_io.8
> +++ b/man/man8/xfs_io.8
> @@ -295,11 +295,12 @@ 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
>
--
To unsubscribe from this list: send the line "unsubscribe linux-xfs" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
