13bd677a47
GFP_NOWAIT allocation can fail anytime - it doesn't wait for memory being available and it fails if the mempool is exhausted and there is not enough memory. If we go down this path: map_bio -> mg_start -> alloc_migration -> mempool_alloc(GFP_NOWAIT) we can see that map_bio() doesn't check the return value of mg_start(), and the bio is leaked. If we go down this path: map_bio -> mg_start -> mg_lock_writes -> alloc_prison_cell -> dm_bio_prison_alloc_cell_v2 -> mempool_alloc(GFP_NOWAIT) -> mg_lock_writes -> mg_complete the bio is ended with an error - it is unacceptable because it could cause filesystem corruption if the machine ran out of memory temporarily. Change GFP_NOWAIT to GFP_NOIO, so that the mempool code will properly wait until memory becomes available. mempool_alloc with GFP_NOIO can't fail, so remove the code paths that deal with allocation failure. Cc: stable@vger.kernel.org Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
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.