[PATCH] virfile: workaround for when posix_fallocate() is not supported by FS

[Roman Bogorodskiy]

posix_fallocate() might be not supported by a filesystem, for example,
it's not supported by ZFS. In that case it fails with
return code 22 (EINVAL), and thus safezero_posix_fallocate() returns -1.

As safezero_posix_fallocate() is the first function tried by safezero()
and it tries other functions only when it returns -2, it fails
immediately without falling back to other methods, such as
safezero_slow().

Fix that by returning -2 if posix_fallocate() returns EINVAL, to give
safezero() a chance to try other functions.

Signed-off-by: Roman Bogorodskiy <bogorodskiy at gmail.com>
---
 src/util/virfile.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/src/util/virfile.c b/src/util/virfile.c
index 609cafdd34..67a350deb3 100644
--- a/src/util/virfile.c
+++ b/src/util/virfile.c
@@ -1119,6 +1119,16 @@ safezero_posix_fallocate(int fd, off_t offset, off_t len)
     int ret = posix_fallocate(fd, offset, len);
     if (ret == 0)
         return 0;
+    else if (ret == EINVAL)
+        /* EINVAL is returned when either:
+           - Operation is not supported by the underlying filesystem,
+           - offset or len argument values are invalid.
+           Assuming that offset and len are valid, this error means
+           the operation is not supported, and we need to fall back
+           to other methods.
+        */
+        return -2;
+
     errno = ret;
     return -1;
 }
-- 
2.30.0