[PATCH v2] cmd: ubi: add a command to swap volumes

[PATCH v2] cmd: ubi: add a command to swap volumes

[Ayoub Zaki]

This commit adds the command ubi swap to swap an ubi volumes.
The format of the command is: ubi swap <volume_a> <volume_b>.
To enable this command, the option CMD_UBI_SWAPVOL must be selected.
---
 cmd/Kconfig |  8 ++++++++
 cmd/ubi.c   | 54 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 62 insertions(+)

diff --git a/cmd/Kconfig b/cmd/Kconfig
index ffef3cc76c..ae0edc9cb1 100644
--- a/cmd/Kconfig
+++ b/cmd/Kconfig
@@ -2381,6 +2381,14 @@ config CMD_UBI_RENAME
          Enable a "ubi" command to rename ubi volume:
 	   ubi rename <oldname> <newname>
 
+config CMD_UBI_SWAPVOL
+       bool "Enable swap volumes"
+       depends on CMD_UBI
+       default n
+       help
+         Enable a "ubi" command to swap ubi volumes:
+	   ubi swap <volume_a> <volume_b>
+
 config CMD_UBIFS
 	tristate "Enable UBIFS - Unsorted block images filesystem commands"
 	depends on CMD_UBI
diff --git a/cmd/ubi.c b/cmd/ubi.c
index fe8ac58bac..43cb3c26a2 100644
--- a/cmd/ubi.c
+++ b/cmd/ubi.c
@@ -289,6 +289,54 @@ static int ubi_rename_vol(char *oldname, char *newname)
 	return ubi_rename_volumes(ubi, &list);
 }
 
+static int ubi_swap_vol(char *volume_a, char *volume_b)
+{
+	struct ubi_volume *vol_a, *vol_b;
+	struct ubi_rename_entry a, b;
+	struct ubi_volume_desc desc_a, desc_b;
+	struct list_head list;
+
+	vol_a = ubi_find_volume(volume_a);
+	if (!vol_a) {
+		printf("%s: volume %s doesn't exist\n", __func__, volume_a);
+		return ENODEV;
+	}
+
+	vol_b = ubi_find_volume(volume_b);
+	if (!vol_b) {
+		printf("%s: volume %s doesn't exist\n", __func__, volume_a);
+		return ENODEV;
+	}
+
+	printf("Swap UBI volumes: %s - %s\n", volume_a, volume_b);
+
+	if (ubi->ro_mode) {
+		printf("%s: ubi device is in read-only mode\n", __func__);
+		return EROFS;
+	}
+
+	a.new_name_len = strlen(volume_a);
+	strcpy(a.new_name, volume_a);
+	a.remove = 0;
+	desc_a.vol = vol_b;
+	desc_a.mode = 0;
+	a.desc = &desc_a;
+
+	b.new_name_len = strlen(volume_b);
+	strcpy(b.new_name, volume_b);
+	b.remove = 0;
+	desc_b.vol = vol_a;
+	desc_b.mode = 0;
+	b.desc = &desc_b;
+
+	INIT_LIST_HEAD(&a.list);
+	INIT_LIST_HEAD(&b.list);
+	INIT_LIST_HEAD(&list);
+	list_add(&a.list, &list);
+	list_add(&b.list, &list);
+	return ubi_rename_volumes(ubi, &list);
+}
+
 static int ubi_volume_continue_write(char *volume, void *buf, size_t size)
 {
 	int err = 1;
@@ -645,6 +693,9 @@ static int do_ubi(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[])
 	if (IS_ENABLED(CONFIG_CMD_UBI_RENAME) && !strncmp(argv[1], "rename", 6))
 		return ubi_rename_vol(argv[2], argv[3]);
 
+	if (IS_ENABLED(CONFIG_CMD_UBI_SWAPVOL) && !strncmp(argv[1], "swap", 4))
+		return ubi_swap_vol(argv[2], argv[3]);
+
 	if (strncmp(argv[1], "skipcheck", 9) == 0) {
 		/* E.g., change skip_check flag */
 		if (argc == 4) {
@@ -735,6 +786,9 @@ U_BOOT_CMD(
 		" - Remove volume\n"
 #if IS_ENABLED(CONFIG_CMD_UBI_RENAME)
 	"ubi rename oldname newname\n"
+#endif
+#if IS_ENABLED(CONFIG_CMD_UBI_SWAPVOL)
+	"ubi swap volume_a volume_b\n"
 #endif
 	"ubi skipcheck volume on/off - Set or clear skip_check flag in volume header\n"
 	"[Legends]\n"
-- 
2.17.1

Re: [PATCH v2] cmd: ubi: add a command to swap volumes

[Heiko Schocher]

Hello Ayoub,

On 09.09.21 13:52, Ayoub Zaki wrote:
> This commit adds the command ubi swap to swap an ubi volumes.
> The format of the command is: ubi swap <volume_a> <volume_b>.
> To enable this command, the option CMD_UBI_SWAPVOL must be selected.
> ---
>  cmd/Kconfig |  8 ++++++++
>  cmd/ubi.c   | 54 +++++++++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 62 insertions(+)

Could you please add a Signed-off-by line?

And please add in further patches a change log [1], may you want
to use patman u-boot:/tools/patman/README

Thanks!

bye,
Heiko
[1] https://www.denx.de/wiki/view/U-Boot/Patches#Sending_updated_patch_versions
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Re: [PATCH v2] cmd: ubi: add a command to swap volumes

[Wolfgang Denk]

Dear Ayoub,

In message <20210909115257.14147-1-ayoub.zaki@embexus.com> you wrote:
> This commit adds the command ubi swap to swap an ubi volumes.
> The format of the command is: ubi swap <volume_a> <volume_b>.
> To enable this command, the option CMD_UBI_SWAPVOL must be selected.

May I ask what this command is good for, i. e. what is the intended
use case?

I have the feeling that you might want to do something which
requires an atomic operation, but you should be aware that the
implementation is NOT atomic - even worse: in case of problems there
is not even a way to fall back to the old state.

So if you think to use this for example for reliable software
updates, then you have a big problem here.

Or am I missing something?

Best regards,

Wolfgang Denk

-- 
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HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd@denx.de
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