On 04/26/2016 09:26 AM, Chandan Rajendra wrote:
Btrfs assumes block size to be the same as the machine's page size. This would mean that a Btrfs instance created on a 4k page size machine (e.g. x86) will not be mountable on machines with larger page sizes (e.g. PPC64/AARCH64). This patchset aims to resolve this incompatibility. This patchset continues with the work posted previously at https://urldefense.proofpoint.com/v2/url?u=http-3A__thread.gmane.org_gmane.comp.file-2Dsystems.btrfs_55257&d=CwIBAg&c=5VD0RTtNlTh3ycd41b3MUw&r=sDzg6MvHymKOUgI8SFIm4Q&m=HOo9J04GyB-3WnF7O0oScGWuin-MaYuh9OMQrAFNE-0&s=ZGXiVRRSCQha83XunflDOkpffSfDEy8OKzFHRud6oXw&e= . I have reverted the upstream commit "btrfs: fix lockups from btrfs_clear_path_blocking" (f82c458a2c3ffb94b431fc6ad791a79df1b3713e) since this led to soft-lockups when the patch "Btrfs: subpagesize-blocksize: Prevent writes to an extent buffer when PG_writeback flag is set" is applied. During 2015's Vault Conference Btrfs meetup, Chris Mason had suggested that he will write up a suitable locking function to be used when writing dirty pages that map metadata blocks. Until we have a suitable locking function available, this patchset temporarily disables the commit f82c458a2c3ffb94b431fc6ad791a79df1b3713e. The commits for the Btrfs kernel module can be found at https://github.com/chandanr/linux/tree/btrfs/subpagesize-blocksize. To create a filesystem with block size < page size, a patched version of the Btrfs-progs package is required. The corresponding fixes for Btrfs-progs can be found at https://github.com/chandanr/btrfs-progs/tree/btrfs/subpagesize-blocksize. Fstests run status: 1. x86_64 - With 4k sectorsize, all the tests that succeed with the master branch at git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux.git branch also do so with the patches applied. 2. ppc64 - With 4k sectorsize, 16k nodesize and with "nospace_cache" mount option, except for scrub and compression tests, all the tests that succeed with the master branch at git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux.git branch also do so with the patches applied. - With 64k sectorsize & nodesize, all the tests that succeed with the master branch at git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux.git branch also do so with the patches applied. TODO: 1. The selftests code needs to be fixed to work in subpage-blocksize scenario. I have currently disabled self-tests from my kernel configuration. We can expect an mail from kbuild indicating a build failure for self-tests code. 2. I am planning to fix Scrub & Compression via a separate patchset.
The selftests need to pass, I don't want to have to deal with kbuild failures and have to remember it's because selftests don't work right with sub page blocksizes. Thanks,
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