On 2017/8/22 16:43, Ulf Hansson wrote:
On 4 August 2017 at 04:51, Shawn Lin <shawn.lin@xxxxxxxxxxxxxx> wrote:
The intention for this patch is to help folks debug the failure
like this:
dwmmc_rockchip fe320000.dwmmc: IDMAC supports 32-bit address mode.
dwmmc_rockchip fe320000.dwmmc: Using internal DMA controller.
dwmmc_rockchip fe320000.dwmmc: Version ID is 270a
dwmmc_rockchip fe320000.dwmmc: DW MMC controller at irq 28,32 bit
host data width,256 deep fifo
dwmmc_rockchip fe320000.dwmmc: Got CD GPIO
mmc_host mmc0: Bus speed (slot 0) = 400000Hz (slot req 400000Hz, actual
400000HZ div = 0)
mmc_host mmc0: Bus speed (slot 0) = 50000000Hz (slot req 50000000Hz,
actual 50000000HZ div = 0)
mmc0: new high speed SDHC card at address 0007
mmcblk: probe of mmc0:0007 failed with error -28
It's quite annoying that some buggy userspace deamon miss the disk remove
uevent sometimes so it would finally make the SD card not work. So from
the dmesg it only shows a errno of -28 but still don't understand what
happened.
For quick reproduce this, we could set max_devices to 8 and run
for i in $(seq 1 9); do
echo "========================" $i
echo fe320000.dwmmc > /sys/bus/platform/drivers/dwmmc_rockchip/unbind
sleep .5
echo fe320000.dwmmc > /sys/bus/platform/drivers/dwmmc_rockchip/bind
sleep .5
mount -t vfat /dev/mmcblk0 /mnt
sleep .5
done
Signed-off-by: Shawn Lin <shawn.lin@xxxxxxxxxxxxxx>
---
drivers/mmc/core/block.c | 18 +++++++++++++++++-
1 file changed, 17 insertions(+), 1 deletion(-)
diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c
index a11bead..3ede32a 100644
--- a/drivers/mmc/core/block.c
+++ b/drivers/mmc/core/block.c
@@ -1985,8 +1985,24 @@ static struct mmc_blk_data *mmc_blk_alloc_req(struct mmc_card *card,
int devidx, ret;
devidx = ida_simple_get(&mmc_blk_ida, 0, max_devices, GFP_KERNEL);
- if (devidx < 0)
+ if (devidx < 0) {
+ /*
+ * The reason for why we could get -ENOSPC here for
+ * removable devices is that probably userspace mount
+ * the partition but forget to umount it which makes
+ * it fail to release md->usage via mmc_blk_release,
+ * so as a result it leaks the device ID and finally
+ * breaks the reference counting for mmc block layer.
+ * It's uerspace's responsibility to guarantee it but
+ * we could cast an explcit error log here to clarify
+ * the situation.
+ */
I would re-phrase the above to something like this:
"We get -ENOSPC because there are no more any available devidx. The
reason may be that userspace haven't yet unmounted the partitions,
which postpones mmc_blk_release() from being called."
That sounds good.
+ if (mmc_card_is_removable(card->host) && devidx == -ENOSPC)
Why not print this error for all type of cards, it seems like relevant
information for the user.
Only if we support booting rootfs from other media and that could
allow modular mmc-blk for non-removable devices. But then static
mmc_blk_ida would be freed anyway. So it won't face this situation?
+ dev_err(mmc_dev(card->host),
+ "possible unblanced mount/umount detected\n");
+
return ERR_PTR(devidx);
+ }
md = kzalloc(sizeof(struct mmc_blk_data), GFP_KERNEL);
if (!md) {
--
1.9.1
Kind regards
Uffe
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