[PATCH 3/4] fiemap: Simplify internals of fiemap_f.

[Nikolay Borisov <nborisov@suse.com>]

So far fiemap used some rather convoluted logic to terminate the iteration and
calculate the number of extents to pass to fm_extent_count. Simplify this by:

* Get the whole number of extents that this file has and keep iterating until
we've printed all extents

* Always use a hard-coded batch of 32 extents so we don't have to worry about
any extra calculations

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
---
 io/fiemap.c | 37 +++++++++++++++++++++----------------
 1 file changed, 21 insertions(+), 16 deletions(-)

diff --git a/io/fiemap.c b/io/fiemap.c
index 30c49112e089..ef54b265ab91 100644
--- a/io/fiemap.c
+++ b/io/fiemap.c
@@ -23,6 +23,8 @@
 #include "init.h"
 #include "io.h"
 
+#define EXTENT_BATCH 32
+
 static cmdinfo_t fiemap_cmd;
 static const __u64 blocksize = 512;
 static int max_extents = 0;
@@ -95,7 +97,7 @@ print_verbose(
 		memset(lbuf, 0, sizeof(lbuf));
 	}
 
-	if ((*cur_extent + 1) == max_extents)
+	if (*cur_extent == max_extents)
 		return;
 
 	snprintf(lbuf, sizeof(lbuf), "[%llu..%llu]:", lstart,
@@ -137,7 +139,7 @@ print_plain(
 		(*cur_extent)++;
 	}
 
-	if ((*cur_extent + 1) == max_extents)
+	if (*cur_extent == max_extents)
 		return;
 
 	printf("\t%d: [%llu..%llu]: %llu..%llu", *cur_extent,
@@ -215,7 +217,7 @@ fiemap_f(
 	char		**argv)
 {
 	struct fiemap	*fiemap;
-	int		num_extents = 32;
+	int		num_extents;
 	int		last = 0;
 	int		lflag = 0;
 	int		vflag = 0;
@@ -251,10 +253,15 @@ fiemap_f(
 		}
 	}
 
-	if (max_extents)
-		num_extents = min(num_extents, max_extents);
+	ret = get_extent_count(file->fd, last_logical, -1);
+	if (ret < 0) {
+		exitcode = 1;
+		return 0;
+	}
+	num_extents = ret;
+
 	map_size = sizeof(struct fiemap) +
-		(num_extents * sizeof(struct fiemap_extent));
+		(EXTENT_BATCH * sizeof(struct fiemap_extent));
 	fiemap = malloc(map_size);
 	if (!fiemap) {
 		fprintf(stderr, _("%s: malloc of %d bytes failed.\n"),
@@ -265,16 +272,14 @@ 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));
+	while (!last && num_extents) {
 
+		/* Query a batch worth of extents */
 		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;
+		fiemap->fm_extent_count = EXTENT_BATCH;
 
 		ret = ioctl(file->fd, FS_IOC_FIEMAP, (unsigned long)fiemap);
 		if (ret < 0) {
@@ -307,17 +312,17 @@ fiemap_f(
 				print_plain(extent, lflag, blocksize,
 					    &cur_extent, &last_logical);
 
-			if (extent->fe_flags & FIEMAP_EXTENT_LAST) {
+			if (extent->fe_flags & FIEMAP_EXTENT_LAST ||
+			    cur_extent == max_extents) {
 				last = 1;
 				break;
 			}
-
-			if ((cur_extent + 1) == max_extents)
-				break;
 		}
+
+		num_extents -= fiemap->fm_mapped_extents;
 	}
 
-	if ((cur_extent + 1) == max_extents)
+	if (cur_extent == max_extents)
 		goto out;
 
 	memset(&st, 0, sizeof(st));
-- 
2.7.4