Re: [PATCH V15 14/18] block: enable multipage bvecs

[Ming Lei]

On Thu, Feb 21, 2019 at 11:22:39AM +0100, Marek Szyprowski wrote:
> Hi Ming,
> 
> On 2019-02-21 11:16, Ming Lei wrote:
> > On Thu, Feb 21, 2019 at 11:08:19AM +0100, Marek Szyprowski wrote:
> >> On 2019-02-21 10:57, Ming Lei wrote:
> >>> On Thu, Feb 21, 2019 at 09:42:59AM +0100, Marek Szyprowski wrote:
> >>>> On 2019-02-15 12:13, Ming Lei wrote:
> >>>>> This patch pulls the trigger for multi-page bvecs.
> >>>>>
> >>>>> Reviewed-by: Omar Sandoval <osandov@xxxxxx>
> >>>>> Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
> >>>> Since Linux next-20190218 I've observed problems with block layer on one
> >>>> of my test devices (Odroid U3 with EXT4 rootfs on SD card). Bisecting
> >>>> this issue led me to this change. This is also the first linux-next
> >>>> release with this change merged. The issue is fully reproducible and can
> >>>> be observed in the following kernel log:
> >>>>
> >>>> sdhci: Secure Digital Host Controller Interface driver
> >>>> sdhci: Copyright(c) Pierre Ossman
> >>>> s3c-sdhci 12530000.sdhci: clock source 2: mmc_busclk.2 (100000000 Hz)
> >>>> s3c-sdhci 12530000.sdhci: Got CD GPIO
> >>>> mmc0: SDHCI controller on samsung-hsmmc [12530000.sdhci] using ADMA
> >>>> mmc0: new high speed SDHC card at address aaaa
> >>>> mmcblk0: mmc0:aaaa SL16G 14.8 GiB
> >>>>
> >>>> ...
> >>>>
> >>>> EXT4-fs (mmcblk0p2): INFO: recovery required on readonly filesystem
> >>>> EXT4-fs (mmcblk0p2): write access will be enabled during recovery
> >>>> EXT4-fs (mmcblk0p2): recovery complete
> >>>> EXT4-fs (mmcblk0p2): mounted filesystem with ordered data mode. Opts: (null)
> >>>> VFS: Mounted root (ext4 filesystem) readonly on device 179:2.
> >>>> devtmpfs: mounted
> >>>> Freeing unused kernel memory: 1024K
> >>>> hub 1-3:1.0: USB hub found
> >>>> Run /sbin/init as init process
> >>>> hub 1-3:1.0: 3 ports detected
> >>>> *** stack smashing detected ***: <unknown> terminated
> >>>> Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000004
> >>>> CPU: 1 PID: 1 Comm: init Not tainted 5.0.0-rc6-next-20190218 #1546
> >>>> Hardware name: SAMSUNG EXYNOS (Flattened Device Tree)
> >>>> [<c01118d0>] (unwind_backtrace) from [<c010d794>] (show_stack+0x10/0x14)
> >>>> [<c010d794>] (show_stack) from [<c09ff8a4>] (dump_stack+0x90/0xc8)
> >>>> [<c09ff8a4>] (dump_stack) from [<c0125944>] (panic+0xfc/0x304)
> >>>> [<c0125944>] (panic) from [<c012bc98>] (do_exit+0xabc/0xc6c)
> >>>> [<c012bc98>] (do_exit) from [<c012c100>] (do_group_exit+0x3c/0xbc)
> >>>> [<c012c100>] (do_group_exit) from [<c0138908>] (get_signal+0x130/0xbf4)
> >>>> [<c0138908>] (get_signal) from [<c010c7a0>] (do_work_pending+0x130/0x618)
> >>>> [<c010c7a0>] (do_work_pending) from [<c0101034>]
> >>>> (slow_work_pending+0xc/0x20)
> >>>> Exception stack(0xe88c3fb0 to 0xe88c3ff8)
> >>>> 3fa0:                                     00000000 bea7787c 00000005
> >>>> b6e8d0b8
> >>>> 3fc0: bea77a18 b6f92010 b6e8d0b8 00000001 b6e8d0c8 00000001 b6e8c000
> >>>> bea77b60
> >>>> 3fe0: 00000020 bea77998 ffffffff b6d52368 60000050 ffffffff
> >>>> CPU3: stopping
> >>>>
> >>>> I would like to help debugging and fixing this issue, but I don't really
> >>>> have idea where to start. Here are some more detailed information about
> >>>> my test system:
> >>>>
> >>>> 1. Board: ARM 32bit Samsung Exynos4412-based Odroid U3 (device tree
> >>>> source: arch/arm/boot/dts/exynos4412-odroidu3.dts)
> >>>>
> >>>> 2. Block device: MMC/SDHCI/SDHCI-S3C with SD card
> >>>> (drivers/mmc/host/sdhci-s3c.c driver, sdhci_2 device node in the device
> >>>> tree)
> >>>>
> >>>> 3. Rootfs: Ext4
> >>>>
> >>>> 4. Kernel config: arch/arm/configs/exynos_defconfig
> >>>>
> >>>> I can gather more logs if needed, just let me which kernel option to
> >>>> enable. Reverting this commit on top of next-20190218 as well as current
> >>>> linux-next (tested with next-20190221) fixes this issue and makes the
> >>>> system bootable again.
> >>> Could you test the patch in following link and see if it can make a difference?
> >>>
> >>> https://marc.info/?l=linux-aio&m=155070355614541&w=2
> >> I've tested that patch, but it doesn't make any difference on the test
> >> system. In the log I see no warning added by it.
> > I guess it might be related with memory corruption, could you enable the
> > following debug options and post the dmesg log?
> >
> > CONFIG_DEBUG_STACKOVERFLOW=y
> > CONFIG_KASAN=y
> 
> It won't be that easy as none of the above options is available on ARM
> 32bit. I will try to apply some ARM KASAN patches floating on the net
> and let you know the result.

Hi Marek,

Could you test the following patch?

diff --git a/block/bounce.c b/block/bounce.c
index add085e28b1d..0c618c0b3cf8 100644
--- a/block/bounce.c
+++ b/block/bounce.c
@@ -295,7 +295,6 @@ static void __blk_queue_bounce(struct request_queue *q, struct bio **bio_orig,
 	bool bounce = false;
 	int sectors = 0;
 	bool passthrough = bio_is_passthrough(*bio_orig);
-	struct bvec_iter_all iter_all;
 
 	bio_for_each_segment(from, *bio_orig, iter) {
 		if (i++ < BIO_MAX_PAGES)
@@ -315,7 +314,8 @@ static void __blk_queue_bounce(struct request_queue *q, struct bio **bio_orig,
 	bio = bounce_clone_bio(*bio_orig, GFP_NOIO, passthrough ? NULL :
 			&bounce_bio_set);
 
-	bio_for_each_segment_all(to, bio, i, iter_all) {
+	/* bio won't be multi-page bvec, so operate its bvec table directly */
+	for (i = 0, to = bio->bi_io_vec; i < bio->bi_vcnt; to++, i++) {
 		struct page *page = to->bv_page;
 
 		if (page_to_pfn(page) <= q->limits.bounce_pfn)

Thanks,
Ming