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1a41802701
bio_set_dev sets a bdev to a bio and is not only setting a pointer bug also changing some state bits if there was a different bdev set before. This is one thing that's not needed. Another thing is that setting a bdev at bio allocation time is too early and actually does not work with plain redundancy profiles, where each time we submit a bio to a device, the bdev is set correctly. In many places the bio bdev is set to latest_bdev that seems to serve as a stub pointer "just to put something to bio". But we don't have to do that. Where do we know which bdev to set: * for regular IO: submit_stripe_bio that's called by btrfs_map_bio * repair IO: repair_io_failure, read or write from specific device * super block write (using buffer_heads but uses raw bdev) and barriers * scrub: this does not use all regular IO paths as it needs to reach all copies, verify and fixup eventually, and for that all bdev management is independent * raid56: rbio_add_io_page, for the RMW write * integrity-checker: does it's own low-level block tracking Signed-off-by: David Sterba <dsterba@suse.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.