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[174.109.172.136]) by smtp.gmail.com with ESMTPSA id 33sm8098682qtc.18.2021.10.13.07.50.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 13 Oct 2021 07:50:39 -0700 (PDT) Date: Wed, 13 Oct 2021 10:50:38 -0400 From: Josef Bacik To: Qu Wenruo , dsterba@suse.com Cc: linux-btrfs@vger.kernel.org Subject: Re: [PATCH v3 20/26] btrfs: make extent_write_locked_range() to be subpage compatible Message-ID: References: <20210927072208.21634-1-wqu@suse.com> <20210927072208.21634-21-wqu@suse.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210927072208.21634-21-wqu@suse.com> Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On Mon, Sep 27, 2021 at 03:22:02PM +0800, Qu Wenruo wrote: > There are two sites are not subpage compatible yet for > extent_write_locked_range(): > > - How @nr_pages are calculated > For subpage we can have the following range with 64K page size: > > 0 32K 64K 96K 128K > | |////|/////| | > > In that case, although 96K - 32K == 64K, thus it looks like one page > is enough, but the range spans across two pages, not one. > > Fix it by doing proper round_up() and round_down() to calculate > @nr_pages. > > Also add some extra ASSERT()s to ensure the range passed in is already > aligned. > > - How the page end is calculated > Currently we just use cur + PAGE_SIZE - 1 to calculate the page end. > > Which can't handle above range layout, and will trigger ASSERT() in > btrfs_writepage_endio_finish_ordered(), as the range is no longer > covered by the page range. > > Fix it by take page end into consideration. > > Signed-off-by: Qu Wenruo > --- > fs/btrfs/extent_io.c | 17 +++++++++++++---- > 1 file changed, 13 insertions(+), 4 deletions(-) > > diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c > index 825917f1b623..f05d8896d1ad 100644 > --- a/fs/btrfs/extent_io.c > +++ b/fs/btrfs/extent_io.c > @@ -5087,15 +5087,14 @@ int extent_write_locked_range(struct inode *inode, u64 start, u64 end) > struct address_space *mapping = inode->i_mapping; > struct page *page; > u64 cur = start; > - unsigned long nr_pages = (end - start + PAGE_SIZE) >> > - PAGE_SHIFT; > + unsigned long nr_pages; > + const u32 sectorsize = btrfs_sb(inode->i_sb)->sectorsize; > struct extent_page_data epd = { > .bio_ctrl = { 0 }, > .extent_locked = 1, > .sync_io = 1, > }; > struct writeback_control wbc_writepages = { > - .nr_to_write = nr_pages * 2, > .sync_mode = WB_SYNC_ALL, > .range_start = start, > .range_end = end + 1, > @@ -5104,14 +5103,24 @@ int extent_write_locked_range(struct inode *inode, u64 start, u64 end) > .no_cgroup_owner = 1, > }; > > + ASSERT(IS_ALIGNED(start, sectorsize) && > + IS_ALIGNED(end + 1, sectorsize)); > + nr_pages = (round_up(end, PAGE_SIZE) - round_down(start, PAGE_SIZE)) >> > + PAGE_SHIFT; > + wbc_writepages.nr_to_write = nr_pages * 2; > + > wbc_attach_fdatawrite_inode(&wbc_writepages, inode); > while (cur <= end) { > + u64 cur_end = min(round_down(cur, PAGE_SIZE) + PAGE_SIZE - 1, > + end); > + > page = find_get_page(mapping, cur >> PAGE_SHIFT); > /* > * All pages in the range are locked since > * btrfs_run_delalloc_range(), thus there is no way to clear > * the page dirty flag. > */ > + ASSERT(PageLocked(page)); We're tripping this ASSERT() with compression turned on, sorry I didn't notice this but we've been panicing consistently since this was merged, so I've lost a weeks worth of xfstests runs. You can easily reproduce running ./check generic/029 with MOUNT_OPTIONS="-o compress" Thanks, Josef