io: use posix_fallocate to allocate disk space

ftruncate does not allocate it, and subsequent access to mmaped
file will result in SIGBUS. this fixes to properly report disk
full errors.

1 files changed, 8 insertions, 3 deletions

diff --git a/src/io.c b/src/io.c
index a62ef36..a321c0c 100644
--- a/src/io.c
+++ b/src/io.c
@@ -144,9 +144,14 @@ size_t apk_istream_splice(void *stream, int fd, size_t size,
 
 	bufsz = size;
 	if (size > 128 * 1024) {
-		if (size != APK_SPLICE_ALL && ftruncate(fd, size) == 0)
-			mmapbase = mmap(NULL, size, PROT_READ | PROT_WRITE,
-					MAP_SHARED, fd, 0);
+		if (size != APK_SPLICE_ALL) {
+			r = posix_fallocate(fd, 0, size);
+			if (r == 0)
+				mmapbase = mmap(NULL, size, PROT_READ | PROT_WRITE,
+						MAP_SHARED, fd, 0);
+			else if (r != ENOSYS)
+				return -r;
+		}
 		if (bufsz > 2*1024*1024)
 			bufsz = 2*1024*1024;
 		buf = mmapbase;