dc8fbb03dc
Function gfs2_free_extlen calculates the length of an extent of free blocks that may be reserved. The end pointer was calculated as end = start + bh->b_size but b_size is incorrect because the bitmap usually stops prior to the end of the buffer data on the last bitmap. What this means is that when you do a write, you can reserve a chunk of blocks that runs off the end of the last bitmap. For example, I've got a file system where there is only one bitmap for each rgrp, so ri_length==1. I saw cases in which iozone tried to do a big write, grabbed a large block reservation, chose rgrp 5464152, which has ri_data0 5464153 and ri_data 8188. So 5464153 + 8188 = 5472341 which is the end of the rgrp. When it grabbed a reservation it got back: 5470936, length 7229. But 5470936 + 7229 = 5478165. So the reservation starts inside the rgrp but runs 5824 blocks past the end of the bitmap. This patch fixes the calculation so it won't exceed the last bitmap. It also adds a BUG_ON to guard against overflows in the future. Signed-off-by: Bob Peterson <rpeterso@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.
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.