SEEK_DATA has interesting behaviour for sparse files on ZFS. A sparse file

with 128K of random data and truncated to 800K can have SEEK_DATA return -1
when given an offset of 128K. On UFS, the SEEK_DATA returns 800K (the size
of the file). SEEK_HOLE on ZFS seems to behave the same as UFS.

To handle this, map -1 to the size of the file (`end') when lseek returns
this for either SEEK_HOLE or SEEK_DATA. When sparse files are not supported
by the file system both `hole' and `data' will now be equal to `end' and we
will treat the entire file as data. This way, the -1 return for SEEK_DATA
on ZFS will end up doing the right thing.

Reported by: gjb@

MFC after:	3 days

1 files changed, 5 insertions, 3 deletions

diff --git a/usr.bin/mkimg/image.c b/usr.bin/mkimg/image.c
index 3e7c7d2..be1c2e9 100644
--- a/usr.bin/mkimg/image.c
+++ b/usr.bin/mkimg/image.c
@@ -405,16 +405,18 @@ image_copyin_mapped(lba_t blk, int fd, uint64_t *sizep)
 	error = 0;
 	while (!error && cur < end) {
 		hole = lseek(fd, cur, SEEK_HOLE);
+		if (hole == -1)
+			hole = end;
 		data = lseek(fd, cur, SEEK_DATA);
+		if (data == -1)
+			data = end;
 
 		/*
 		 * Treat the entire file as data if sparse files
 		 * are not supported by the underlying file system.
 		 */
-		if (hole == -1 && data == -1) {
+		if (hole == end && data == end)
 			data = cur;
-			hole = end;
-		}
 
 		if (cur == hole && data > hole) {
 			hole = pos;