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Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1qWyTd-009N6I-UG; Fri, 18 Aug 2023 12:21:17 +0000 Date: Fri, 18 Aug 2023 13:21:17 +0100 From: Matthew Wilcox To: Mirsad Todorovac Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Andrew Morton , linux-mm@kvack.org, Chris Mason , Josef Bacik , David Sterba , linux-btrfs@vger.kernel.org Subject: Re: [BUG] KCSAN: data-race in xas_clear_mark / xas_find_marked Message-ID: References: <06645d2b-a964-1c4c-15cf-42ccc6c6e19b@alu.unizg.hr> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <06645d2b-a964-1c4c-15cf-42ccc6c6e19b@alu.unizg.hr> X-Rspamd-Queue-Id: 42D9A40007 X-Rspam-User: X-Rspamd-Server: rspam04 X-Stat-Signature: 4pfkcxi141bjybhffc5deqosexk13fge X-HE-Tag: 1692361286-91642 X-HE-Meta: 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 Rt8lcK8W 8PTE7vClzHgtz3pEinPrdFUc7eVwAd7HVckh5LfYMFpBWA90uPlsohdv3BqOJeYKu95lMYlZiqxg7P15VJERomCdAGihEpIZZ/9n052fGkO0Rp/Up3+4VX76ZHyjmB496Dx1lPVKTtuPVxagOl++v/RF4yual77s/Ri4nCoths/QhuNr7jinOoG2oDw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000128, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, Aug 18, 2023 at 10:01:32AM +0200, Mirsad Todorovac wrote: > [ 206.510010] ================================================================== > [ 206.510035] BUG: KCSAN: data-race in xas_clear_mark / xas_find_marked > > [ 206.510067] write to 0xffff963df6a90fe0 of 8 bytes by interrupt on cpu 22: > [ 206.510081] xas_clear_mark+0xd5/0x180 > [ 206.510097] __xa_clear_mark+0xd1/0x100 > [ 206.510114] __folio_end_writeback+0x293/0x5a0 > [ 206.520722] read to 0xffff963df6a90fe0 of 8 bytes by task 2793 on cpu 6: > [ 206.520735] xas_find_marked+0xe5/0x600 > [ 206.520750] filemap_get_folios_tag+0xf9/0x3d0 Also, before submitting this kind of report, you should run the trace through scripts/decode_stacktrace.sh to give us line numbers instead of hex offsets, which are useless to anyone who doesn't have your exact kernel build. > [ 206.510010] ================================================================== > [ 206.510035] BUG: KCSAN: data-race in xas_clear_mark / xas_find_marked > > [ 206.510067] write to 0xffff963df6a90fe0 of 8 bytes by interrupt on cpu 22: > [ 206.510081] xas_clear_mark (./arch/x86/include/asm/bitops.h:178 ./include/asm-generic/bitops/instrumented-non-atomic.h:115 lib/xarray.c:102 lib/xarray.c:914) > [ 206.510097] __xa_clear_mark (lib/xarray.c:1923) > [ 206.510114] __folio_end_writeback (mm/page-writeback.c:2981) This path is properly using xa_lock_irqsave() before calling __xa_clear_mark(). > [ 206.520722] read to 0xffff963df6a90fe0 of 8 bytes by task 2793 on cpu 6: > [ 206.520735] xas_find_marked (./include/linux/xarray.h:1706 lib/xarray.c:1354) > [ 206.520750] filemap_get_folios_tag (mm/filemap.c:1975 mm/filemap.c:2273) This takes the RCU read lock before calling xas_find_marked() as it's supposed to. What garbage do I have to write to tell KCSAN it's wrong? The line that's probably triggering it is currently: unsigned long data = *addr & (~0UL << offset);