[PATCH 2/2] fiemap: Implement ranged query

Nikolay Borisov
2017-10-27T12:37:20Z

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. This also requires changing
of how the final hole range is calculated. Namely, it's now being done as
[last_logical, logical addres of next extent] rather than being statically
determined by [last_logical, filesize]. Also now fiemap explicitly
prints if a file consists of only a hole rather than staying silent.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
---
io/fiemap.c | 72 +++++++++++++++++++++++++++++++++++++++++++++++--------
man/man8/xfs_io.8 | 5 ++--
2 files changed, 65 insertions(+), 12 deletions(-)

diff --git a/io/fiemap.c b/io/fiemap.c
index 4a52bff974e8..56bfb1a5f2d5 100644
--- a/io/fiemap.c
+++ b/io/fiemap.c
@@ -27,6 +27,9 @@

static cmdinfo_t fiemap_cmd;
static int max_extents = -1;
+static __u64 covered_length = 0;
+static __u64 len = -1LL;
+static bool range_limit = false;

static void
fiemap_help(void)
@@ -79,7 +82,7 @@ print_hole(
boff_w, _("hole"), tot_w, lstart - llast);
}

-
+ covered_length += BBTOB(lstart - llast);
}

static int
@@ -90,7 +93,8 @@ print_verbose(
int tot_w,
int flg_w,
int cur_extent,
- __u64 last_logical)
+ __u64 last_logical,
+ __u64 limit)
{
__u64 lstart;
__u64 llast;
@@ -122,7 +126,7 @@ print_verbose(
cur_extent++;
}

- if (cur_extent == max_extents)
+ if (cur_extent == max_extents || (range_limit && covered_length >= limit))
return 1;

snprintf(lbuf, sizeof(lbuf), "[%llu..%llu]:", lstart,
@@ -140,7 +144,8 @@ print_plain(
struct fiemap_extent *extent,
int lflag,
int cur_extent,
- __u64 last_logical)
+ __u64 last_logical,
+ __u64 limit)
{
__u64 lstart;
__u64 llast;
@@ -157,7 +162,7 @@ print_plain(
cur_extent++;
}

- if (cur_extent == max_extents)
+ if (cur_extent == max_extents || (range_limit && covered_length >= limit))
return 1;

printf("\t%d: [%llu..%llu]: %llu..%llu", cur_extent,
@@ -255,8 +260,11 @@ fiemap_f(
int tot_w = 5; /* 5 since its just one number */
int flg_w = 5;
__u64 last_logical = 0;
+ size_t fsblocksize, fssectsize;
struct stat st;

+ init_cvtnum(&fsblocksize, &fssectsize);
+
while ((c = getopt(argc, argv, "aln:v")) != EOF) {
switch (c) {
case 'a':
@@ -276,6 +284,26 @@ fiemap_f(
}
}

+ if (optind < argc) {
+ 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;
+ 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;
+ range_limit = true;
+ }
+
map_size = sizeof(struct fiemap) +
(EXTENT_BATCH * sizeof(struct fiemap_extent));
fiemap = malloc(map_size);
@@ -316,14 +344,18 @@ fiemap_f(
num_printed = print_verbose(extent, foff_w,
boff_w, tot_w,
flg_w, cur_extent,
- last_logical);
+ last_logical,
+ len);
} else
num_printed = print_plain(extent, lflag,
cur_extent,
- last_logical);
+ last_logical,
+ len);

cur_extent += num_printed;
last_logical = extent->fe_logical + extent->fe_length;
+ if (num_printed == 2)
+ covered_length += extent->fe_length;

if (extent->fe_flags & FIEMAP_EXTENT_LAST) {
last = 1;
@@ -332,6 +364,9 @@ fiemap_f(

if (cur_extent == max_extents)
break;
+
+ if (range_limit && covered_length >= len)
+ goto out;
}
}

@@ -347,9 +382,26 @@ fiemap_f(
return 0;
}

- if (cur_extent && last_logical < st.st_size)
+ if (last_logical < st.st_size &&
+ (!range_limit || covered_length < len)) {
+ int end;
+
+ ret = __fiemap(fiemap, map_size, fiemap_flags, last_logical,
+ st.st_size);
+ if (ret < 0) {
+ exitcode = 1;
+ goto out;
+ }
+
+ if (!fiemap->fm_mapped_extents)
+ end = BTOBBT(st.st_size);
+ else
+ end = BTOBBT(fiemap->fm_extents[0].fe_logical);
+
+
print_hole(foff_w, boff_w, tot_w, cur_extent, lflag, !vflag,
- BTOBBT(last_logical), BTOBBT(st.st_size));
+ BTOBBT(last_logical), end);
+ }

out:
free(fiemap);
@@ -364,7 +416,7 @@ 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 0fd9b951199c..27f1ae163913 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
--
2.7.4