[JFFS2] Add erase block summary support (mount time improvement)

The goal of summary is to speed up the mount time. Erase block summary (EBS)
stores summary information at the end of every (closed) erase block. It is
no longer necessary to scan all nodes separetly (and read all pages of them)
just read this "small" summary, where every information is stored which is
needed at mount time.

This summary information is stored in a JFFS2_FEATURE_RWCOMPAT_DELETE. During
the mount process if there is no summary info the orignal scan process will
be executed. EBS works with NAND and NOR flashes, too.

There is a user space tool called sumtool to generate this summary
information for a JFFS2 image.

Signed-off-by: Ferenc Havasi <havasi@inf.u-szeged.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 13 insertions, 0 deletions

diff --git a/fs/Kconfig b/fs/Kconfig
index 01a295232f75..37d86c5072eb 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -1050,6 +1050,19 @@ config JFFS2_FS_WRITEBUFFER
 	    - NOR flash with transparent ECC
 	    - DataFlash
 
+config JFFS2_SUMMARY
+	bool "JFFS2 summary support (EXPERIMENTAL)"
+	depends on JFFS2_FS && EXPERIMENTAL
+	default n
+	help
+	  This feature makes it possible to use summary information
+	  for faster filesystem mount.
+
+	  The summary information can be inserted into a filesystem image
+	  by the utility 'sumtool'.
+
+	  If unsure, say 'N'.
+
 config JFFS2_COMPRESSION_OPTIONS
 	bool "Advanced compression options for JFFS2"
 	depends on JFFS2_FS