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Message-Id: <20211008143825.3717116-1-sean@geanix.com>
Date: Fri, 8 Oct 2021 16:38:24 +0200
From: Sean Nyekjaer <sean@...nix.com>
To: Boris Brezillon <boris.brezillon@...labora.com>
Cc: Sean Nyekjaer <sean@...nix.com>,
Miquel Raynal <miquel.raynal@...tlin.com>,
Richard Weinberger <richard@....at>,
Vignesh Raghavendra <vigneshr@...com>,
Boris Brezillon <bbrezillon@...nel.org>,
linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [RFC PATCH 1/2] mtd: core: protect access to mtd devices while in suspend
This will prevent reading/writing/erasing to a suspended mtd device.
It will force mtd_write()/mtd_read()/mtd_erase() to wait for
mtd_resume() to unlock access to mtd devices.
Exec_op[0] speed things up, so we see this race when rawnand devices going
into suspend. But it's actually "mtd: rawnand: Simplify the locking" that
allows it to return errors rather than locking, before that commit it would
have waited for the rawnand device to resume.
Tested on a iMX6ULL.
[0]:
ef347c0cfd61 ("mtd: rawnand: gpmi: Implement exec_op")
Fixes: 013e6292aaf5 ("mtd: rawnand: Simplify the locking")
Signed-off-by: Sean Nyekjaer <sean@...nix.com>
---
Hope I got it all :)
drivers/mtd/mtdcore.c | 57 ++++++++++++++++++++++++++++++++++++++++-
include/linux/mtd/mtd.h | 36 ++++++++++++++++++--------
2 files changed, 81 insertions(+), 12 deletions(-)
diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
index c8fd7f758938..3c93202e6cbb 100644
--- a/drivers/mtd/mtdcore.c
+++ b/drivers/mtd/mtdcore.c
@@ -36,6 +36,44 @@
struct backing_dev_info *mtd_bdi;
+static void mtd_start_access(struct mtd_info *mtd)
+{
+ struct mtd_info *master = mtd_get_master(mtd);
+
+ /*
+ * Don't take the suspend_lock on devices that don't
+ * implement the suspend hook. Otherwise, lockdep will
+ * complain about nested locks when trying to suspend MTD
+ * partitions or MTD devices created by gluebi which are
+ * backed by real devices.
+ */
+ if (!master->_suspend)
+ return;
+
+ /*
+ * Wait until the device is resumed. Should we have a
+ * non-blocking mode here?
+ */
+ while (1) {
+ down_read(&master->master.suspend_lock);
+ if (!master->master.suspended)
+ return;
+
+ up_read(&master->master.suspend_lock);
+ wait_event(master->master.resume_wq, master->master.suspended == 0);
+ }
+}
+
+static void mtd_end_access(struct mtd_info *mtd)
+{
+ struct mtd_info *master = mtd_get_master(mtd);
+
+ if (!master->_suspend)
+ return;
+
+ up_read(&master->master.suspend_lock);
+}
+
#ifdef CONFIG_PM_SLEEP
static int mtd_cls_suspend(struct device *dev)
@@ -1000,6 +1038,9 @@ int mtd_device_parse_register(struct mtd_info *mtd, const char * const *types,
ret = mtd_otp_nvmem_add(mtd);
+ init_waitqueue_head(&mtd->master.resume_wq);
+ init_rwsem(&mtd->master.suspend_lock);
+
out:
if (ret && device_is_registered(&mtd->dev))
del_mtd_device(mtd);
@@ -1241,6 +1282,8 @@ int mtd_erase(struct mtd_info *mtd, struct erase_info *instr)
struct erase_info adjinstr;
int ret;
+ mtd_start_access(mtd);
+
instr->fail_addr = MTD_FAIL_ADDR_UNKNOWN;
adjinstr = *instr;
@@ -1278,6 +1321,8 @@ int mtd_erase(struct mtd_info *mtd, struct erase_info *instr)
}
}
+ mtd_end_access(mtd);
+
return ret;
}
EXPORT_SYMBOL_GPL(mtd_erase);
@@ -1558,6 +1603,8 @@ int mtd_read_oob(struct mtd_info *mtd, loff_t from, struct mtd_oob_ops *ops)
struct mtd_ecc_stats old_stats = master->ecc_stats;
int ret_code;
+ mtd_start_access(mtd);
+
ops->retlen = ops->oobretlen = 0;
ret_code = mtd_check_oob_ops(mtd, from, ops);
@@ -1577,6 +1624,8 @@ int mtd_read_oob(struct mtd_info *mtd, loff_t from, struct mtd_oob_ops *ops)
mtd_update_ecc_stats(mtd, master, &old_stats);
+ mtd_end_access(mtd);
+
/*
* In cases where ops->datbuf != NULL, mtd->_read_oob() has semantics
* similar to mtd->_read(), returning a non-negative integer
@@ -1597,6 +1646,8 @@ int mtd_write_oob(struct mtd_info *mtd, loff_t to,
struct mtd_info *master = mtd_get_master(mtd);
int ret;
+ mtd_start_access(mtd);
+
ops->retlen = ops->oobretlen = 0;
if (!(mtd->flags & MTD_WRITEABLE))
@@ -1615,7 +1666,11 @@ int mtd_write_oob(struct mtd_info *mtd, loff_t to,
if (mtd->flags & MTD_SLC_ON_MLC_EMULATION)
return mtd_io_emulated_slc(mtd, to, false, ops);
- return mtd_write_oob_std(mtd, to, ops);
+ ret = mtd_write_oob_std(mtd, to, ops);
+
+ mtd_end_access(mtd);
+
+ return ret;
}
EXPORT_SYMBOL_GPL(mtd_write_oob);
diff --git a/include/linux/mtd/mtd.h b/include/linux/mtd/mtd.h
index 88227044fc86..cfab07b02dc9 100644
--- a/include/linux/mtd/mtd.h
+++ b/include/linux/mtd/mtd.h
@@ -231,6 +231,8 @@ struct mtd_master {
struct mutex partitions_lock;
struct mutex chrdev_lock;
unsigned int suspended : 1;
+ wait_queue_head_t resume_wq;
+ struct rw_semaphore suspend_lock;
};
struct mtd_info {
@@ -546,30 +548,42 @@ int mtd_block_markbad(struct mtd_info *mtd, loff_t ofs);
static inline int mtd_suspend(struct mtd_info *mtd)
{
struct mtd_info *master = mtd_get_master(mtd);
- int ret;
+ int ret = 0;
- if (master->master.suspended)
- return 0;
- ret = master->_suspend ? master->_suspend(master) : 0;
- if (ret)
+ if (!master->_suspend)
return ret;
- master->master.suspended = 1;
- return 0;
+ down_write(&master->master.suspend_lock);
+ if (!master->master.suspended) {
+ ret = master->_suspend(master);
+ if (!ret)
+ master->master.suspended = 1;
+ }
+ up_write(&master->master.suspend_lock);
+
+ return ret;
}
static inline void mtd_resume(struct mtd_info *mtd)
{
struct mtd_info *master = mtd_get_master(mtd);
- if (!master->master.suspended)
+ if (!master->_suspend)
return;
- if (master->_resume)
- master->_resume(master);
- master->master.suspended = 0;
+ down_write(&master->master.suspend_lock);
+ if (master->master.suspended) {
+ if (master->_resume)
+ master->_resume(master);
+
+ master->master.suspended = 0;
+
+ /* The MTD dev has been resumed, wake up all waiters. */
+ wake_up_all(&master->master.resume_wq);
+ }
+ up_write(&master->master.suspend_lock);
}
static inline uint32_t mtd_div_by_eb(uint64_t sz, struct mtd_info *mtd)
--
2.33.0
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