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Message-ID: <20240907-ubi-wl-race-v1-1-6f7f5e0aea7b@axis.com>
Date: Sat, 7 Sep 2024 21:28:26 +0200
From: Mårten Lindahl <marten.lindahl@...s.com>
To: Richard Weinberger <richard@....at>, Zhihao Cheng
<chengzhihao1@...wei.com>, Miquel Raynal <miquel.raynal@...tlin.com>,
"Vignesh Raghavendra" <vigneshr@...com>
CC: <linux-mtd@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
<kernel@...s.com>, Mårten Lindahl <marten.lindahl@...s.com>
Subject: [PATCH] ubi: wl: Close down wear-leveling before nand is suspended
If a reboot/shutdown signal with double force (-ff) is triggered when
the erase worker or wear-leveling worker function runs we may end up in
a race condition since the MTD device gets a reboot notification and
suspends the nand flash before the erase or wear-leveling is done. This
will reject all accesses to the flash with -EBUSY.
Sequence for the erase worker function:
systemctl reboot -ff ubi_thread
do_work
__do_sys_reboot
blocking_notifier_call_chain
mtd_reboot_notifier
nand_shutdown
nand_suspend
__erase_worker
ubi_sync_erase
mtd_erase
nand_erase_nand
# Blocked by suspended chip
nand_get_device
=> EBUSY
Similar sequence for the wear-leveling function:
systemctl reboot -ff ubi_thread
do_work
__do_sys_reboot
blocking_notifier_call_chain
mtd_reboot_notifier
nand_shutdown
nand_suspend
wear_leveling_worker
ubi_eba_copy_leb
ubi_io_write
mtd_write
nand_write_oob
# Blocked by suspended chip
nand_get_device
=> EBUSY
systemd-shutdown[1]: Rebooting.
ubi0 error: ubi_io_write: error -16 while writing 2048 bytes to PEB
CPU: 1 PID: 82 Comm: ubi_bgt0d Kdump: loaded Tainted: G O
(unwind_backtrace) from [<80107b9f>] (show_stack+0xb/0xc)
(show_stack) from [<8033641f>] (dump_stack_lvl+0x2b/0x34)
(dump_stack_lvl) from [<803b7f3f>] (ubi_io_write+0x3ab/0x4a8)
(ubi_io_write) from [<803b817d>] (ubi_io_write_vid_hdr+0x71/0xb4)
(ubi_io_write_vid_hdr) from [<803b6971>] (ubi_eba_copy_leb+0x195/0x2f0)
(ubi_eba_copy_leb) from [<803b939b>] (wear_leveling_worker+0x2ff/0x738)
(wear_leveling_worker) from [<803b86ef>] (do_work+0x5b/0xb0)
(do_work) from [<803b9ee1>] (ubi_thread+0xb1/0x11c)
(ubi_thread) from [<8012c113>] (kthread+0x11b/0x134)
(kthread) from [<80100139>] (ret_from_fork+0x11/0x38)
Exception stack(0x80c43fb0 to 0x80c43ff8)
...
ubi0 error: ubi_dump_flash: err -16 while reading 2048 bytes from PEB
ubi0 error: wear_leveling_worker: error -16 while moving PEB 246 to PEB
ubi0 warning: ubi_ro_mode.part.0: switch to read-only mode
...
ubi0 error: do_work: work failed with error code -16
ubi0 error: ubi_thread: ubi_bgt0d: work failed with error code -16
...
Kernel panic - not syncing: Software Watchdog Timer expired
Add a reboot notification for the ubi/wear-leveling to shutdown any
potential flash work actions before the nand is suspended.
Signed-off-by: Mårten Lindahl <marten.lindahl@...s.com>
---
drivers/mtd/ubi/ubi.h | 2 ++
drivers/mtd/ubi/wl.c | 21 +++++++++++++++++++++
2 files changed, 23 insertions(+)
diff --git a/drivers/mtd/ubi/ubi.h b/drivers/mtd/ubi/ubi.h
index 1c9e874e8ede..4a48ed0ecdb6 100644
--- a/drivers/mtd/ubi/ubi.h
+++ b/drivers/mtd/ubi/ubi.h
@@ -549,6 +549,7 @@ struct ubi_debug_info {
* @peb_buf: a buffer of PEB size used for different purposes
* @buf_mutex: protects @peb_buf
* @ckvol_mutex: serializes static volume checking when opening
+ * @wl_reboot_notifier: close all wear-leveling work before reboot
*
* @dbg: debugging information for this UBI device
*/
@@ -651,6 +652,7 @@ struct ubi_device {
void *peb_buf;
struct mutex buf_mutex;
struct mutex ckvol_mutex;
+ struct notifier_block wl_reboot_notifier;
struct ubi_debug_info dbg;
};
diff --git a/drivers/mtd/ubi/wl.c b/drivers/mtd/ubi/wl.c
index a357f3d27f2f..b3484e9e969c 100644
--- a/drivers/mtd/ubi/wl.c
+++ b/drivers/mtd/ubi/wl.c
@@ -89,6 +89,7 @@
#include <linux/crc32.h>
#include <linux/freezer.h>
#include <linux/kthread.h>
+#include <linux/reboot.h>
#include "ubi.h"
#include "wl.h"
@@ -127,6 +128,8 @@ static int self_check_in_wl_tree(const struct ubi_device *ubi,
struct ubi_wl_entry *e, struct rb_root *root);
static int self_check_in_pq(const struct ubi_device *ubi,
struct ubi_wl_entry *e);
+static int ubi_wl_reboot_notifier(struct notifier_block *n,
+ unsigned long state, void *cmd);
/**
* wl_tree_add - add a wear-leveling entry to a WL RB-tree.
@@ -1943,6 +1946,13 @@ int ubi_wl_init(struct ubi_device *ubi, struct ubi_attach_info *ai)
if (!ubi->ro_mode && !ubi->fm_disabled)
ubi_ensure_anchor_pebs(ubi);
#endif
+
+ if (!ubi->wl_reboot_notifier.notifier_call) {
+ ubi->wl_reboot_notifier.notifier_call = ubi_wl_reboot_notifier;
+ ubi->wl_reboot_notifier.priority = 1; /* Higher than MTD */
+ register_reboot_notifier(&ubi->wl_reboot_notifier);
+ }
+
return 0;
out_free:
@@ -1988,6 +1998,17 @@ void ubi_wl_close(struct ubi_device *ubi)
kfree(ubi->lookuptbl);
}
+static int ubi_wl_reboot_notifier(struct notifier_block *n,
+ unsigned long state, void *cmd)
+{
+ struct ubi_device *ubi;
+
+ ubi = container_of(n, struct ubi_device, wl_reboot_notifier);
+ ubi_wl_close(ubi);
+
+ return NOTIFY_DONE;
+}
+
/**
* self_check_ec - make sure that the erase counter of a PEB is correct.
* @ubi: UBI device description object
---
base-commit: 431c1646e1f86b949fa3685efc50b660a364c2b6
change-id: 20240903-ubi-wl-race-e039db89122f
Best regards,
--
Mårten Lindahl <marten.lindahl@...s.com>
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