NeilBrown
689389a06c
handle_read_error() duplicates a lot of the work that raid1_read_request() does, so it makes sense to just use that function. This doesn't quite work as handle_read_error() relies on the same r1bio being re-used so that, in the case of a read-only array, setting IO_BLOCKED in r1bio->bios[] ensures read_balance() won't re-use that device. So we need to allow a r1bio to be passed to raid1_read_request(), and to have that function mostly initialise the r1bio, but leave the bios[] array untouched. Two parts of handle_read_error() that need to be preserved are the warning message it prints, so they are conditionally added to raid1_read_request(). Note that this highlights a minor bug on alloc_r1bio(). It doesn't initalise the bios[] array, so it is possible that old content is there, which might cause read_balance() to ignore some devices with no good reason. With this change, we no longer need inc_pending(), or the sectors_handled arg to alloc_r1bio(). As handle_read_error() is called from raid1d() and allocates memory, there is tiny chance of a deadlock. All element of various pools could be queued waiting for raid1 to handle them, and there may be no extra memory free. Achieving guaranteed forward progress would probably require a second thread and another mempool. Instead of that complexity, add __GFP_HIGH to any allocations when read1_read_request() is called from raid1d. Signed-off-by: NeilBrown <neilb@suse.com> Signed-off-by: Shaohua Li <shli@fb.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.