ubifs: introduce UBIFS_ATIME_SUPPORT to ubifs

To make ubifs support atime flexily, this commit introduces
a Kconfig option named as UBIFS_ATIME_SUPPORT.

With UBIFS_ATIME_SUPPORT=n:
	ubifs keeps the full compatibility to no_atime from
the start of ubifs.

=================UBIFS_ATIME_SUPPORT=n=======================
-o - no atime
-o atime - no atime
-o noatime - no atime
-o relatime - no atime
-o strictatime - no atime
-o lazyatime - no atime

With UBIFS_ATIME_SUPPORT=y:
	ubifs supports the atime same with other main stream
file systems.
=================UBIFS_ATIME_SUPPORT=y=======================
-o - default behavior (relatime currently)
-o atime - atime support
-o noatime - no atime support
-o relatime - relative atime support
-o strictatime - strict atime support
-o lazyatime - lazy atime support

Signed-off-by: Dongsheng Yang <yangds.fnst@cn.fujitsu.com>
Reviewed-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Richard Weinberger <richard@nod.at>

1 files changed, 15 insertions, 0 deletions

diff --git a/fs/ubifs/Kconfig b/fs/ubifs/Kconfig
index ba66d508..7ff7712 100644
--- a/fs/ubifs/Kconfig
+++ b/fs/ubifs/Kconfig
@@ -35,3 +35,18 @@ config UBIFS_FS_ZLIB
 	default y
 	help
 	  Zlib compresses better than LZO but it is slower. Say 'Y' if unsure.
+
+config UBIFS_ATIME_SUPPORT
+	bool "Access time support" if UBIFS_FS
+	depends on UBIFS_FS
+	default n
+	help
+	  Originally UBIFS did not support atime, because it looked like a bad idea due
+	  increased flash wear. This option adds atime support and it is disabled by default
+	  to preserve the old behavior. If you enable this option, UBIFS starts updating atime,
+	  which means that file-system read operations will cause writes (inode atime
+	  updates). This may affect file-system performance and increase flash device wear,
+	  so be careful. How often atime is updated depends on the selected strategy:
+	  strictatime is the "heavy", relatime is "lighter", etc.
+
+	  If unsure, say 'N'