[PATCH 2/2] xfs_io: don't count fsmaps before querying fsmaps

["Darrick J. Wong" <djwong@kernel.org>]

From: Darrick J. Wong <djwong@kernel.org>

There's a bunch of code in fsmap.c that tries to count the GETFSMAP
records so that it can size the fsmap array appropriately for the
GETFSMAP call.  It's pointless to iterate the entire result set /twice/
(unlike the bmap command where the extent count is actually stored in
the fs metadata), so get rid of the duplicate walk.

In other words: Iterate over the records using the default chunk size
instead of doing one call to find the size and doing a giant allocation
and GETFSMAP call.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 io/fsmap.c |   30 ------------------------------
 1 file changed, 30 deletions(-)


diff --git a/io/fsmap.c b/io/fsmap.c
index 9f179fa8..f540a7c0 100644
--- a/io/fsmap.c
+++ b/io/fsmap.c
@@ -372,13 +372,11 @@ fsmap_f(
 	char			**argv)
 {
 	struct fsmap		*p;
-	struct fsmap_head	*nhead;
 	struct fsmap_head	*head;
 	struct fsmap		*l, *h;
 	struct xfs_fsop_geom	fsgeo;
 	long long		start = 0;
 	long long		end = -1;
-	int			nmap_size;
 	int			map_size;
 	int			nflag = 0;
 	int			vflag = 0;
@@ -492,34 +490,6 @@ fsmap_f(
 	h->fmr_flags = UINT_MAX;
 	h->fmr_offset = ULLONG_MAX;
 
-	/* Count mappings */
-	if (!nflag) {
-		head->fmh_count = 0;
-		i = ioctl(file->fd, FS_IOC_GETFSMAP, head);
-		if (i < 0) {
-			fprintf(stderr, _("%s: xfsctl(XFS_IOC_GETFSMAP)"
-				" iflags=0x%x [\"%s\"]: %s\n"),
-				progname, head->fmh_iflags, file->name,
-				strerror(errno));
-			exitcode = 1;
-			free(head);
-			return 0;
-		}
-		if (head->fmh_entries > map_size + 2) {
-			map_size = 11ULL * head->fmh_entries / 10;
-			nmap_size = map_size > (1 << 24) ? (1 << 24) : map_size;
-			nhead = realloc(head, fsmap_sizeof(nmap_size));
-			if (nhead == NULL) {
-				fprintf(stderr,
-					_("%s: cannot realloc %zu bytes\n"),
-					progname, fsmap_sizeof(nmap_size));
-			} else {
-				head = nhead;
-				map_size = nmap_size;
-			}
-		}
-	}
-
 	/*
 	 * If this is an XFS filesystem, remember the data device.
 	 * (We report AG number/block for data device extents on XFS).