[PATCH 2/3] punch-alternating: use the block size reported by the fs for punching

["Darrick J. Wong" <darrick.wong@xxxxxxxxxx>]

When we're trying to punch alternating blocks out of a file, use the
bsize reported by fstatfs so that we can punch out single blocks.

Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
---
 src/punch-alternating.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)


diff --git a/src/punch-alternating.c b/src/punch-alternating.c
index 9566310..4148622 100644
--- a/src/punch-alternating.c
+++ b/src/punch-alternating.c
@@ -14,6 +14,7 @@
 int main(int argc, char *argv[])
 {
        struct stat     s;
+       struct statfs   sf;
        off_t           offset;
        int             fd;
        blksize_t       blksz;
@@ -35,8 +36,12 @@ int main(int argc, char *argv[])
        if (error)
                goto err;
 
+       error = fstatfs(fd, &sf);
+       if (error)
+               goto err;
+
        sz = s.st_size;
-       blksz = s.st_blksize;
+       blksz = sf.f_bsize;
 
        mode = FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE;
        for (offset = 0; offset < sz; offset += blksz * 2) {