xfs_io: implement ranged fiemap query

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@suse.com>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
[sandeen: simplify/rewrite ranged logic]
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>

2 files changed, 78 insertions, 17 deletions

diff --git a/io/fiemap.c b/io/fiemap.c
index bdcfacdb28..2f12652648 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 9bf1a4783c..fabf92f367 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