From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Brian Cain" Subject: RE: [PATCH] btrfs: Disable BTRFS on platforms having 256K pages Date: Sat, 12 Jun 2021 09:44:05 -0500 Message-ID: <17a401d75f99$662cdc50$328694f0$@codeaurora.org> References: <185278AF-1D87-432D-87E9-C86B3223113E@fb.com> Reply-To: bcain@codeaurora.org Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Return-path: DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mg.codeaurora.org; q=dns/txt; s=smtp; t=1623509055; h=Content-Transfer-Encoding: Content-Type: MIME-Version: Message-ID: Date: Subject: In-Reply-To: References: Cc: To: From: Reply-To: Sender; bh=RhtvN2QTW0JZFH6Rjd3vbX9yOl+YFdfv0SB17b2868c=; b=k0HU4kB5Cyx6FrM/UIBPtCIku1SKtbNjdCm9wl6ykARbxvMzDtHf5oqEpfpOJe17LrWSELhO OsEP+QVb+qX6QF4AFBPSkjfzRj+kgdlWXtNsFguU9/dT3Cp9FtzFU6WxOpqM5sIzToBLH9NY qG3COBjl82y1Nzt2ZNaMMdzX88M= In-Reply-To: Content-Language: en-us List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linuxppc-dev-bounces+glppe-linuxppc-embedded-2=m.gmane-mx.org@lists.ozlabs.org Sender: "Linuxppc-dev" Content-Type: text/plain; charset="utf-8" To: 'Christophe Leroy' , 'Chris Mason' Cc: linux-hexagon@vger.kernel.org, 'Josef Bacik' , linux-kernel@vger.kernel.org, 'David Sterba' , linuxppc-dev@lists.ozlabs.org, 'linux-btrfs' > -----Original Message----- > From: Christophe Leroy ... > Le 10/06/2021 =C3=A0 15:54, Chris Mason a =C3=A9crit : > > > >> On Jun 10, 2021, at 1:23 AM, Christophe Leroy > wrote: > >> > >> With a config having PAGE_SIZE set to 256K, BTRFS build fails > >> with the following message > >> > >> include/linux/compiler_types.h:326:38: error: call to > '__compiletime_assert_791' declared with attribute error: BUILD_BUG_ON > failed: (BTRFS_MAX_COMPRESSED % PAGE_SIZE) !=3D 0 > >> > >> BTRFS_MAX_COMPRESSED being 128K, BTRFS cannot support platforms > with > >> 256K pages at the time being. > >> > >> There are two platforms that can select 256K pages: > >> - hexagon > >> - powerpc > >> > >> Disable BTRFS when 256K page size is selected. > >> > > > > We=E2=80=99ll have other subpage blocksize concerns with 256K pages, = but this > BTRFS_MAX_COMPRESSED #define is arbitrary. It=E2=80=99s just trying = to have an > upper bound on the amount of memory we=E2=80=99ll need to uncompress a = single > page=E2=80=99s worth of random reads. > > > > We could change it to max(PAGE_SIZE, 128K) or just bump to 256K. > > >=20 > But if 256K is problematic in other ways, is it worth bumping > BTRFS_MAX_COMPRESSED to 256K ? >=20 > David, in below mail, said that 256K support would require deaper = changes. So > disabling BTRFS > support seems the easiest solution for the time being, at least for = Stable (I > forgot the Fixes: tag > and the CC: to stable). >=20 > On powerpc, 256k pages is a corner case, it requires customised = binutils, so I > don't think disabling > BTRFS is a issue there. For hexagon I don't know. Larger page sizes like this are typical for hexagon. Disabling btrfs on = hexagon seems appropriate. -Brian