[PATCH] xfs_db: add alignment filter to freesp command

[Eric Sandeen <sandeen@redhat.com>]

This adds an alignment filter to the xfs_db freesp command, i.e.

xfs_db> freesp -A 4

will show only 4-block aligned free extents.

This can be useful for finding freespace suitable for allocations
with specific alignment requirements, such as inode allocation.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
---

diff --git a/db/freesp.c b/db/freesp.c
index 27e9f5a..c3ca2f3 100644
--- a/db/freesp.c
+++ b/db/freesp.c
@@ -54,6 +54,7 @@ static int	usage(void);
 
 static int		agcount;
 static xfs_agnumber_t	*aglist;
+static int		alignment;
 static int		countflag;
 static int		dumpflag;
 static int		equalsize;
@@ -67,7 +68,7 @@ static long long	totexts;
 
 static const cmdinfo_t	freesp_cmd =
 	{ "freesp", NULL, freesp_f, 0, -1, 0,
-	  "[-bcdfs] [-a agno]... [-e binsize] [-h h1]... [-m binmult]",
+	  "[-bcdfs] [-A alignment] [-a agno]... [-e binsize] [-h h1]... [-m binmult]",
 	  "summarize free space for filesystem", NULL };
 
 static int
@@ -147,8 +148,11 @@ init(
 	totblocks = totexts = 0;
 	aglist = NULL;
 	hist = NULL;
-	while ((c = getopt(argc, argv, "a:bcde:h:m:s")) != EOF) {
+	while ((c = getopt(argc, argv, "A:a:bcde:h:m:s")) != EOF) {
 		switch (c) {
+		case 'A':
+			alignment = atoi(optarg);
+			break;
 		case 'a':
 			aglistadd(optarg);
 			break;
@@ -372,6 +376,9 @@ addtohist(
 {
 	int		i;
 
+	if (alignment && (XFS_AGB_TO_FSB(mp,agno,agbno) % alignment))
+		return;
+
 	if (dumpflag)
 		dbprintf("%8d %8d %8d\n", agno, agbno, len);
 	totexts++;
diff --git a/man/man8/xfs_db.8 b/man/man8/xfs_db.8
index 460d89d..2c89769 100644
--- a/man/man8/xfs_db.8
+++ b/man/man8/xfs_db.8
@@ -512,12 +512,17 @@ enables processing of realtime control file data.
 enables processing of realtime file data.
 .RE
 .TP
-.BI "freesp [\-bcds] [\-a " ag "] ... [\-e " i "] [\-h " h1 "] ... [\-m " m ]
+.BI "freesp [\-bcds] [\-A " alignment "] [\-a " ag "] ... [\-e " i "] [\-h " h1 "] ... [\-m " m ]
 Summarize free space for the filesystem. The free blocks are examined
 and totalled, and displayed in the form of a histogram, with a count
 of extents in each range of free extent sizes.
 .RS 1.0i
 .TP 0.4i
+.B \-A
+reports only free extents with starting blocks aligned to
+.I alignment
+blocks.
+.TP
 .B \-a
 adds
 .I ag