Merge tag 'upstream-3.7-rc1-fastmap' of git://git.infradead.org/linux-ubi

Pull UBI fastmap changes from Artem Bityutskiy:
 "This pull request contains the UBI fastmap support implemented by
  Richard Weinberger from Linutronix.  Fastmap is designed to address
  UBI's slow scanning issues.  Namely, it introduces a new on-flash
  data-structure called "fastmap", which stores the information about
  logical<->physical eraseblocks mappings.  So now to get this
  information just read the fastmap, instead of doing full scan.  More
  information here can be found in Richard's announcement in LKML
  (Subject: UBI: Fastmap request for inclusion (v19)):

     http://thread.gmane.org/gmane.linux.kernel/1364922/focus=1369109

  One thing I want to explicitly say is that fastmap did not have large
  enough linux-next exposure.  It is partially my fault - I did not
  respond quickly enough.  I _really_ apologize for this.  But it had
  good testing and disabled by default, so I do not expect that we'll
  break anything.

  Fastmap is declared as experimental so far, and it is off by default.
  We did declare that the on-flash format may be changed.  The reason
  for this is that no one used it in real production so far, so there is
  a high risk that something is missing.  Besides, we do not have
  user-space tools supporting fastmap so far.

  Nevertheless, I suggest we merge this feature.  Many people want UBI's
  scanning bottleneck to be fixed and merging fastmap now should
  accelerate its production use.  The plan is to make it bullet-prove,
  somewhat clean-up, and make it the default for UBI.  I do not know how
  many kernel releases will it take.

  Basically, I what I want to do for fastmap is something like Linus did
  for btrfs few years ago."

* tag 'upstream-3.7-rc1-fastmap' of git://git.infradead.org/linux-ubi:
  UBI: Wire-up fastmap
  UBI: Add fastmap core
  UBI: Add fastmap support to the WL sub-system
  UBI: Add fastmap stuff to attach.c
  UBI: Wire-up ->fm_sem
  UBI: Add fastmap bits to build.c
  UBI: Add self_check_eba()
  UBI: Export next_sqnum()
  UBI: Add fastmap stuff to ubi.h
  UBI: Add fastmap on-flash data structures

1 files changed, 21 insertions, 0 deletions

diff --git a/drivers/mtd/ubi/Kconfig b/drivers/mtd/ubi/Kconfig
index 271a842f8c3..36663af56d8 100644
--- a/drivers/mtd/ubi/Kconfig
+++ b/drivers/mtd/ubi/Kconfig
@@ -56,6 +56,27 @@ config MTD_UBI_BEB_LIMIT
 
 	  Leave the default value if unsure.
 
+config MTD_UBI_FASTMAP
+	bool "UBI Fastmap (Experimental feature)"
+	default n
+	help
+	   Important: this feature is experimental so far and the on-flash
+	   format for fastmap may change in the next kernel versions
+
+	   Fastmap is a mechanism which allows attaching an UBI device
+	   in nearly constant time. Instead of scanning the whole MTD device it
+	   only has to locate a checkpoint (called fastmap) on the device.
+	   The on-flash fastmap contains all information needed to attach
+	   the device. Using fastmap makes only sense on large devices where
+	   attaching by scanning takes long. UBI will not automatically install
+	   a fastmap on old images, but you can set the UBI module parameter
+	   fm_autoconvert to 1 if you want so. Please note that fastmap-enabled
+	   images are still usable with UBI implementations without
+	   fastmap support. On typical flash devices the whole fastmap fits
+	   into one PEB. UBI will reserve PEBs to hold two fastmaps.
+
+	   If in doubt, say "N".
+
 config MTD_UBI_GLUEBI
 	tristate "MTD devices emulation driver (gluebi)"
 	help