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.
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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
e9eca4de95