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a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1744707946; bh=Jk1eZdnZg7G5vh0w7ZZMU2B0/djohjlF/9UhwnoXVqM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=EnDaFjaoBbP4Ukx95bRanjXNjAhy3CPInDT7xMQPQ9yzQiJf4C55jyHbKIXkNhxVl hJysns7LjdmPe0fO2wmPSEbzyBco46UODoD0j+j+kl3v3SU44XIrnewY70CWY37OeK pfLLQ72QvzY1o9jaww271/RexBEWW2Dl2FA48OmMXBYk28jE3aJtnOQxnsAPsIchGC pfwPrGPaUGI5eSOZZxjBYpPhQyunRS/kpgzS9eXFsfU4F3k3uVEEOzlVcLpJLcKmmP /j5uUgwzbKjkCVPJL18oLf9pDxhAsBPH7tvvbjaZVAi9mx15ZVUEYXjLdU1fB9dN69 /jeeXnNuBORqw== Date: Tue, 15 Apr 2025 11:05:38 +0200 From: Christian Brauner To: Luis Chamberlain Cc: Jan Kara , tytso@mit.edu, adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org, riel@surriel.com, dave@stgolabs.net, willy@infradead.org, hannes@cmpxchg.org, oliver.sang@intel.com, david@redhat.com, axboe@kernel.dk, hare@suse.de, david@fromorbit.com, djwong@kernel.org, ritesh.list@gmail.com, linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, linux-mm@kvack.org, gost.dev@samsung.com, p.raghav@samsung.com, da.gomez@samsung.com, syzbot+f3c6fda1297c748a7076@syzkaller.appspotmail.com Subject: Re: [PATCH v2 1/8] migrate: fix skipping metadata buffer heads on migration Message-ID: <20250415-freihalten-tausend-a9791b9c3a03@brauner> References: <20250410014945.2140781-1-mcgrof@kernel.org> <20250410014945.2140781-2-mcgrof@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: BE2A31C0006 X-Stat-Signature: h7h33kyp96tqfma6qb9tx7uwpoewp53k X-HE-Tag: 1744707947-330965 X-HE-Meta: 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 xgrF1djy brBL9PKhSob8bJLty6GNCSZP1tjX6piGddaJ+RB++MnOchGORimQuTjRaYY5s6FOIUVp+nsPmnxKcLOFKocALx5pSRQc2SB6dyLl4H0ytPgJyue6s2sZ5U31MtOAPSxqdmFbp17Yt5VoB4v5TK1uDQXaiE4VtJNEWzJAunKAkD4t5S6v5Ri1ikJoAacDYhvBAgTojSt36vq/3c9bQVA23gqDFH18kLWb9L/Or5YjUiHc03HsCUJO4s56S9oNQQ24y6uFg+6j1aJNgQfigjT+2IsD88d3C2Iw3K4h7etj6uRTSz+kut7BCG7zSwCOeCfhN/4Q+erjAEfnJIWUUVwh03CkMVqUrrVc0ddaMCcncT00+QD+LGbVxm3RCGPCdCNiivliZD4qC2o7VLJ6zB3sUL0LrQw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Apr 14, 2025 at 03:19:33PM -0700, Luis Chamberlain wrote: > On Mon, Apr 14, 2025 at 02:09:46PM -0700, Luis Chamberlain wrote: > > On Thu, Apr 10, 2025 at 02:05:38PM +0200, Jan Kara wrote: > > > > @@ -859,12 +862,12 @@ static int __buffer_migrate_folio(struct address_space *mapping, > > > > } > > > > bh = bh->b_this_page; > > > > } while (bh != head); > > > > + spin_unlock(&mapping->i_private_lock); > > > > > > No, you've just broken all simple filesystems (like ext2) with this patch. > > > You can reduce the spinlock critical section only after providing > > > alternative way to protect them from migration. So this should probably > > > happen at the end of the series. > > > > So you're OK with this spin lock move with the other series in place? > > > > And so we punt the hard-to-reproduce corruption issue as future work > > to do? Becuase the other alternative for now is to just disable > > migration for jbd2: > > > > diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c > > index 1dc09ed5d403..ef1c3ef68877 100644 > > --- a/fs/ext4/inode.c > > +++ b/fs/ext4/inode.c > > @@ -3631,7 +3631,6 @@ static const struct address_space_operations ext4_journalled_aops = { > > .bmap = ext4_bmap, > > .invalidate_folio = ext4_journalled_invalidate_folio, > > .release_folio = ext4_release_folio, > > - .migrate_folio = buffer_migrate_folio_norefs, > > .is_partially_uptodate = block_is_partially_uptodate, > > .error_remove_folio = generic_error_remove_folio, > > .swap_activate = ext4_iomap_swap_activate, > > BTW I ask because.. are your expectations that the next v3 series also > be a target for Linus tree as part of a fix for this spinlock > replacement? Since this is fixing potential filesystem corruption I will upstream whatever we need to do to fix this. Ideally we have a minimal fix to upstream now and a comprehensive fix and cleanup for v6.16.