From: Anton Ivanov <anton.ivanov@cambridgegreys.com>
Date: Wed, 22 Apr 2020 16:00:01 +0000 (+0100)
Subject: um: Use fdatasync() when mapping the UBD FSYNC command
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=54ebe4060fe6c4ab76c79354417612ac9cf4f95e;p=linux.git

um: Use fdatasync() when mapping the UBD FSYNC command

We do not need to update the metadata (atime, mtime, etc)
on the UBD file and/or the COW file until UML exits.

UBD image mtime is checked in UML only when opening
the files. After that they are locked and used
exclusively by a single UML instance, so there is
no point wasting resources on updating metadata on
every sync. We can sync data only. The host will
always update mtime if a file has been modified upon
closing it.

Signed-off-by: Anton Ivanov <anton.ivanov@cambridgegreys.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
---

diff --git a/arch/um/os-Linux/file.c b/arch/um/os-Linux/file.c
index 044836ad73927..e4421dbc4c36c 100644
--- a/arch/um/os-Linux/file.c
+++ b/arch/um/os-Linux/file.c
@@ -290,7 +290,7 @@ int os_write_file(int fd, const void *buf, int len)
 
 int os_sync_file(int fd)
 {
-	int n = fsync(fd);
+	int n = fdatasync(fd);
 
 	if (n < 0)
 		return -errno;