Re: [PATCH] block: allow device to have both virt_boundary_mask and max segment size

[Ming Lei <ming.lei@redhat.com>]

On Wed, Apr 24, 2024 at 12:26:26PM +0200, Geert Uytterhoeven wrote:
> 	Hi Ming,
> 
> On Sun, 7 Apr 2024, Ming Lei wrote:
> > When one stacking device is over one device with virt_boundary_mask and
> > another one with max segment size, the stacking device have both limits
> > set. This way is allowed before d690cb8ae14b ("block: add an API to
> > atomically update queue limits").
> > 
> > Relax the limit so that we won't break such kind of stacking setting.
> > 
> > Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218687
> > Reported-by: janpieter.sollie@edpnet.be
> > Fixes: d690cb8ae14b ("block: add an API to atomically update queue limits")
> > Link: https://lore.kernel.org/linux-block/ZfGl8HzUpiOxCLm3@fedora/
> > Cc: Christoph Hellwig <hch@lst.de>
> > Cc: Mike Snitzer <snitzer@kernel.org>
> > Cc: dm-devel@lists.linux.dev
> > Cc: Song Liu <song@kernel.org>
> > Cc: linux-raid@vger.kernel.org
> > Signed-off-by: Ming Lei <ming.lei@redhat.com>
> 
> Thanks for your patch, which is now commit b561ea56a26415bf ("block:
> allow device to have both virt_boundary_mask and max segment size") in
> v6.9-rc4.
> 
> With CONFIG_DMA_API_DEBUG_SG=y and IOMMU support enabled, this causes a
> warning on R-Car Gen3/Gen4 platforms:
> 
>     DMA-API: renesas_sdhi_internal_dmac ee160000.mmc: mapping sg segment longer than device claims to support [len=86016] [max=65536]
>     WARNING: CPU: 1 PID: 281 at kernel/dma/debug.c:1178 debug_dma_map_sg+0x2ac/0x330
>     Modules linked in:
>     CPU: 1 PID: 281 Comm: systemd-udevd Tainted: G        W          6.9.0-rc2-ebisu-00012-gb561ea56a264 #596
>     Hardware name: Renesas Ebisu board based on r8a77990 (DT)
>     pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
>     pc : debug_dma_map_sg+0x2ac/0x330
>     lr : debug_dma_map_sg+0x2ac/0x330
>     sp : ffffffc083643470
>     x29: ffffffc083643470 x28: 0000000000000080 x27: 0000000000010000
>     x26: 0000000000000000 x25: 0000000000000001 x24: ffffffc0810afc30
>     x23: ffffffffffffffff x22: ffffffc080c8366f x21: ffffff8008849f80
>     x20: ffffff800cd24000 x19: ffffff80099a2810 x18: 0000000000000000
>     x17: ffffff800801a000 x16: ffffffc080453f00 x15: ffffffc0836430f0
>     x14: ffffffc08099fb50 x13: 0000000000000007 x12: 0000000000000000
>     x11: 0000000000000202 x10: ffffffc0810d99d0 x9 : ffffffc081189bb0
>     x8 : ffffffc083643178 x7 : ffffffc083643180 x6 : 00000000ffffdfff
>     x5 : 0000000000000000 x4 : 0000000000000000 x3 : 0000000000000000
>     x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffffff800ebad280
>     Call trace:
>      debug_dma_map_sg+0x2ac/0x330
>      __dma_map_sg_attrs+0xcc/0xd0
>      dma_map_sg_attrs+0xc/0x1c
>      renesas_sdhi_internal_dmac_map+0x64/0x94
>      renesas_sdhi_internal_dmac_pre_req+0x20/0x2c
>      mmc_blk_mq_issue_rq+0x62c/0x6c8
>      mmc_mq_queue_rq+0x194/0x218
>      blk_mq_dispatch_rq_list+0x36c/0x4d4
>      __blk_mq_sched_dispatch_requests+0x344/0x4e0
>      blk_mq_sched_dispatch_requests+0x28/0x5c
>      blk_mq_run_hw_queue+0x1a4/0x218
>      blk_mq_flush_plug_list+0x2fc/0x4a0
>      __blk_flush_plug+0x70/0x134
>      blk_finish_plug+0x24/0x34
>      read_pages+0x60/0x158
>      page_cache_ra_unbounded+0x98/0x184
>      do_page_cache_ra+0x44/0x50
>      force_page_cache_ra+0x98/0x9c
>      page_cache_sync_ra+0x30/0x54
>      filemap_get_pages+0xfc/0x4f8
>      filemap_read+0xe8/0x2b8
>      blkdev_read_iter+0x12c/0x144
>      vfs_read+0x104/0x150
>      ksys_read+0x6c/0xd4
>      __arm64_sys_read+0x14/0x1c
>      invoke_syscall+0x70/0xf4
>      el0_svc_common.constprop.0+0xb0/0xcc
>      do_el0_svc+0x1c/0x24
>      el0_svc+0x34/0x8c
>      el0t_64_sync_handler+0x88/0x124
>      el0t_64_sync+0x150/0x154
>     irq event stamp: 0
>     hardirqs last  enabled at (0): [<0000000000000000>] 0x0
>     hardirqs last disabled at (0): [<ffffffc08007efa4>] copy_process+0x6ac/0x18d4
>     softirqs last  enabled at (0): [<ffffffc08007efa4>] copy_process+0x6ac/0x18d4
>     softirqs last disabled at (0): [<0000000000000000>] 0x0
> 
> Reverting this commit, or disabling IOMMU support fixes the issue.

Hello Geert,

Can you test the following patch?


diff --git a/block/blk-settings.c b/block/blk-settings.c
index 8e1d7ed52fef..ebba05a2bc7f 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -188,7 +188,10 @@ static int blk_validate_limits(struct queue_limits *lim)
 	 * bvec and lower layer bio splitting is supposed to handle the two
 	 * correctly.
 	 */
-	if (!lim->virt_boundary_mask) {
+	if (lim->virt_boundary_mask) {
+		if (!lim->max_segment_size)
+			lim->max_segment_size = UINT_MAX;
+	} else {
 		/*
 		 * The maximum segment size has an odd historic 64k default that
 		 * drivers probably should override.  Just like the I/O size we

thanks
Ming