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commitde89afc1e4upstream. Following a system crash, dm-era fails to recover the committed writeset for the current era, leading to lost writes. That is, we lose the information about what blocks were written during the affected era. dm-era assumes that the writeset of the current era is archived when the device is suspended. So, when resuming the device, it just moves on to the next era, ignoring the committed writeset. This assumption holds when the device is properly shut down. But, when the system crashes, the code that suspends the target never runs, so the writeset for the current era is not archived. There are three issues that cause the committed writeset to get lost: 1. dm-era doesn't load the committed writeset when opening the metadata 2. The code that resizes the metadata wipes the information about the committed writeset (assuming it was loaded at step 1) 3. era_preresume() starts a new era, without taking into account that the current era might not have been archived, due to a system crash. To fix this: 1. Load the committed writeset when opening the metadata 2. Fix the code that resizes the metadata to make sure it doesn't wipe the loaded writeset 3. Fix era_preresume() to check for a loaded writeset and archive it, before starting a new era. Fixes:eec40579d8("dm: add era target") Cc: stable@vger.kernel.org # v3.15+ Signed-off-by: Nikos Tsironis <ntsironis@arrikto.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.