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commit9c343784c4upstream. Nikolay noticed a bunch of test failures with my global rsv steal patches. At first he thought they were introduced by them, but they've been failing for a while with 64k nodes. The problem is with 64k nodes we have a global reserve that calculates out to 13MiB on a freshly made file system, which only has 8MiB of metadata space. Because of changes I previously made we no longer account for the global reserve in the overcommit logic, which means we correctly allow overcommit to happen even though we are already overcommitted. However in some corner cases, for example btrfs/170, we will allocate the entire file system up with data chunks before we have enough space pressure to allocate a metadata chunk. Then once the fs is full we ENOSPC out because we cannot overcommit and the global reserve is taking up all of the available space. The most ideal way to deal with this is to change our space reservation stuff to take into account the height of the tree's that we're modifying, so that our global reserve calculation does not end up so obscenely large. However that is a huge undertaking. Instead fix this by forcing a chunk allocation if the global reserve is larger than the total metadata space. This gives us essentially the same behavior that happened before, we get a chunk allocated and these tests can pass. This is meant to be a stop-gap measure until we can tackle the "tree height only" project. Fixes:0096420adb("btrfs: do not account global reserve in can_overcommit") CC: stable@vger.kernel.org # 5.4+ Reviewed-by: Nikolay Borisov <nborisov@suse.com> Tested-by: Nikolay Borisov <nborisov@suse.com> Signed-off-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: David Sterba <dsterba@suse.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.