Re: [PATCH v5 3/3] mtd: core: introduce of support for dynamic partitions

From: han.xu
Date: Mon Oct 17 2022 - 16:00:45 EST

On 22/06/06 05:14PM, Ansuel Smith wrote:
> We have many parser that register mtd partitions at runtime. One example
> is the cmdlinepart or the smem-part parser where the compatible is defined
> in the dts and the partitions gets detected and registered by the
> parser. This is problematic for the NVMEM subsystem that requires an OF node
> to detect NVMEM cells.
>
> To fix this problem, introduce an additional logic that will try to
> assign an OF node to the MTD if declared.
>
> On MTD addition, it will be checked if the MTD has an OF node and if
> not declared will check if a partition with the same label is
> declared in DTS. If an exact match is found, the partition dynamically
> allocated by the parser will have a connected OF node.
>
> The NVMEM subsystem will detect the OF node and register any NVMEM cells
> declared statically in the DTS.
>
> Signed-off-by: Ansuel Smith <ansuelsmth@xxxxxxxxx>
> ---
> drivers/mtd/mtdcore.c | 49 +++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 49 insertions(+)
>
> diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
> index 7731796024e0..807194efb580 100644
> --- a/drivers/mtd/mtdcore.c
> +++ b/drivers/mtd/mtdcore.c
> @@ -546,6 +546,54 @@ static int mtd_nvmem_add(struct mtd_info *mtd)
> return 0;
> }
>
> +static void mtd_check_of_node(struct mtd_info *mtd)
> +{
> + struct device_node *partitions, *parent_dn, *mtd_dn = NULL;
> + struct mtd_info *parent;
> + const char *mtd_name;
> + bool found = false;
> + int plen;
> +
> + /* Check if MTD already has a device node */
> + if (dev_of_node(&mtd->dev))
> + return;
> +
> + /* Check if a partitions node exist */
> + parent = mtd->parent;
> + parent_dn = dev_of_node(&parent->dev);
> + if (!parent_dn)
> + return;
> +
> + partitions = of_get_child_by_name(parent_dn, "partitions");
> + if (!partitions)
> + goto exit_parent;
> +
> + /* Search if a partition is defined with the same name */
> + for_each_child_of_node(partitions, mtd_dn) {
> + /* Skip partition with no label */
> + mtd_name = of_get_property(mtd_dn, "label", &plen);
> + if (!mtd_name)
> + continue;
> +
> + if (!strncmp(mtd->name, mtd_name, plen)) {
> + found = true;
> + break;
> + }
> + }
> +
> + if (!found)
> + goto exit_partitions;
> +
> + /* Set of_node only for nvmem */
> + if (of_device_is_compatible(mtd_dn, "nvmem-cells"))
> + mtd_set_of_node(mtd, mtd_dn);
> +
> +exit_partitions:
> + of_node_put(partitions);
> +exit_parent:
> + of_node_put(parent_dn);
> +}
> +
> /**
> * add_mtd_device - register an MTD device
> * @mtd: pointer to new MTD device info structure
> @@ -651,6 +699,7 @@ int add_mtd_device(struct mtd_info *mtd)
> mtd->dev.devt = MTD_DEVT(i);
> dev_set_name(&mtd->dev, "mtd%d", i);
> dev_set_drvdata(&mtd->dev, mtd);
> + mtd_check_of_node(mtd);
> of_node_get(mtd_get_of_node(mtd));
> error = device_register(&mtd->dev);
> if (error)

NXP GPMI NAND controller with 6 cmdline partitions meets refcount underflow
with this patch. The of_node_put(parent_dn) doesn't work with cmdline parser and
causes the issue.

[ 1.078910] 6 cmdlinepart partitions found on MTD device gpmi-nand
[ 1.085116] Creating 6 MTD partitions on "gpmi-nand":
[ 1.090181] 0x000000000000-0x000008000000 : "nandboot"
[ 1.096952] 0x000008000000-0x000009000000 : "nandfit"
[ 1.103547] 0x000009000000-0x00000b000000 : "nandkernel"
[ 1.110317] 0x00000b000000-0x00000c000000 : "nanddtb"
[ 1.115525] ------------[ cut here ]------------
[ 1.120141] refcount_t: addition on 0; use-after-free.
[ 1.125328] WARNING: CPU: 0 PID: 1 at lib/refcount.c:25 refcount_warn_saturate+0xdc/0x148
[ 1.133528] Modules linked in:
[ 1.136589] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 6.0.0-rc7-next-20220930-04543-g8cf3f7
[ 1.146342] Hardware name: Freescale i.MX8DXL DDR3L EVK (DT)
[ 1.151999] pstate: 600000c5 (nZCv daIF -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[ 1.158965] pc : refcount_warn_saturate+0xdc/0x148
[ 1.163760] lr : refcount_warn_saturate+0xdc/0x148
[ 1.168556] sp : ffff800009ddb080
[ 1.171866] x29: ffff800009ddb080 x28: ffff800009ddb35a x27: 0000000000000002
[ 1.179015] x26: ffff8000098b06ad x25: ffffffffffffffff x24: ffff0a00ffffff05
[ 1.186165] x23: ffff00001fdf6470 x22: ffff800009ddb367 x21: 0000000000000000
[ 1.193314] x20: ffff00001fdfebe8 x19: ffff00001fdfec50 x18: ffffffffffffffff
[ 1.200464] x17: 0000000000000000 x16: 0000000000000118 x15: 0000000000000004
[ 1.207614] x14: 0000000000000fff x13: ffff800009bca248 x12: 0000000000000003
[ 1.214764] x11: 00000000ffffefff x10: c0000000ffffefff x9 : 4762cb2ccb52de00
[ 1.221914] x8 : 4762cb2ccb52de00 x7 : 205d313431303231 x6 : 312e31202020205b
[ 1.229063] x5 : ffff800009d55c1f x4 : 0000000000000001 x3 : 0000000000000000
[ 1.236213] x2 : 0000000000000000 x1 : ffff800009954be6 x0 : 000000000000002a
[ 1.243365] Call trace:
[ 1.245806] refcount_warn_saturate+0xdc/0x148
[ 1.250253] kobject_get+0x98/0x9c
[ 1.253658] of_node_get+0x20/0x34
[ 1.257072] of_fwnode_get+0x3c/0x54
[ 1.260652] fwnode_get_nth_parent+0xd8/0xf4
[ 1.264926] fwnode_full_name_string+0x3c/0xb4
[ 1.269373] device_node_string+0x498/0x5b4
[ 1.273561] pointer+0x41c/0x5d0
[ 1.276793] vsnprintf+0x4d8/0x694
[ 1.280198] vprintk_store+0x164/0x528
[ 1.283951] vprintk_emit+0x98/0x164
[ 1.287530] vprintk_default+0x44/0x6c
[ 1.291284] vprintk+0xf0/0x134
[ 1.294428] _printk+0x54/0x7c
[ 1.297486] of_node_release+0xe8/0x128
[ 1.301326] kobject_put+0x98/0xfc
[ 1.304732] of_node_put+0x1c/0x28
[ 1.308137] add_mtd_device+0x484/0x6d4
[ 1.311977] add_mtd_partitions+0xf0/0x1d0
[ 1.316078] parse_mtd_partitions+0x45c/0x518
[ 1.320439] mtd_device_parse_register+0xb0/0x274
[ 1.325147] gpmi_nand_probe+0x51c/0x650
[ 1.329074] platform_probe+0xa8/0xd0
[ 1.332740] really_probe+0x130/0x334
[ 1.336406] __driver_probe_device+0xb4/0xe0
[ 1.340681] driver_probe_device+0x3c/0x1f8
[ 1.344869] __driver_attach+0xdc/0x1a4
[ 1.348708] bus_for_each_dev+0x80/0xcc
[ 1.352548] driver_attach+0x24/0x30
[ 1.356127] bus_add_driver+0x108/0x1f4
[ 1.359967] driver_register+0x78/0x114
[ 1.363807] __platform_driver_register+0x24/0x30
[ 1.368515] gpmi_nand_driver_init+0x1c/0x28
[ 1.372798] do_one_initcall+0xbc/0x238
[ 1.376638] do_initcall_level+0x94/0xb4
[ 1.380565] do_initcalls+0x54/0x94
[ 1.384058] do_basic_setup+0x1c/0x28
[ 1.387724] kernel_init_freeable+0x110/0x188
[ 1.392084] kernel_init+0x20/0x1a0
[ 1.395578] ret_from_fork+0x10/0x20
[ 1.399157] ---[ end trace 0000000000000000 ]---
[ 1.403782] ------------[ cut here ]------------


> --
> 2.36.1
>
>
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