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Subject[PATCH 5.4 118/215] regmap: debugfs: Dont sleep while atomic for fast_io regmaps
Date
From: Douglas Anderson <dianders@chromium.org>

[ Upstream commit 299632e54b2e692d2830af84be51172480dc1e26 ]

If a regmap has "fast_io" set then its lock function uses a spinlock.
That doesn't work so well with the functions:
* regmap_cache_only_write_file()
* regmap_cache_bypass_write_file()

Both of the above functions have the pattern:
1. Lock the regmap.
2. Call:
debugfs_write_file_bool()
copy_from_user()
__might_fault()
__might_sleep()

Let's reorder things a bit so that we do all of our sleepable
functions before we grab the lock.

Fixes: d3dc5430d68f ("regmap: debugfs: Allow writes to cache state settings")
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/20200715164611.1.I35b3533e8a80efde0cec1cc70f71e1e74b2fa0da@changeid
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/base/regmap/regmap-debugfs.c | 52 ++++++++++++++++------------
1 file changed, 29 insertions(+), 23 deletions(-)

diff --git a/drivers/base/regmap/regmap-debugfs.c b/drivers/base/regmap/regmap-debugfs.c
index e72843fe41dfe..e16afa27700db 100644
--- a/drivers/base/regmap/regmap-debugfs.c
+++ b/drivers/base/regmap/regmap-debugfs.c
@@ -457,29 +457,31 @@ static ssize_t regmap_cache_only_write_file(struct file *file,
{
struct regmap *map = container_of(file->private_data,
struct regmap, cache_only);
- ssize_t result;
- bool was_enabled, require_sync = false;
+ bool new_val, require_sync = false;
int err;

- map->lock(map->lock_arg);
+ err = kstrtobool_from_user(user_buf, count, &new_val);
+ /* Ignore malforned data like debugfs_write_file_bool() */
+ if (err)
+ return count;

- was_enabled = map->cache_only;
+ err = debugfs_file_get(file->f_path.dentry);
+ if (err)
+ return err;

- result = debugfs_write_file_bool(file, user_buf, count, ppos);
- if (result < 0) {
- map->unlock(map->lock_arg);
- return result;
- }
+ map->lock(map->lock_arg);

- if (map->cache_only && !was_enabled) {
+ if (new_val && !map->cache_only) {
dev_warn(map->dev, "debugfs cache_only=Y forced\n");
add_taint(TAINT_USER, LOCKDEP_STILL_OK);
- } else if (!map->cache_only && was_enabled) {
+ } else if (!new_val && map->cache_only) {
dev_warn(map->dev, "debugfs cache_only=N forced: syncing cache\n");
require_sync = true;
}
+ map->cache_only = new_val;

map->unlock(map->lock_arg);
+ debugfs_file_put(file->f_path.dentry);

if (require_sync) {
err = regcache_sync(map);
@@ -487,7 +489,7 @@ static ssize_t regmap_cache_only_write_file(struct file *file,
dev_err(map->dev, "Failed to sync cache %d\n", err);
}

- return result;
+ return count;
}

static const struct file_operations regmap_cache_only_fops = {
@@ -502,28 +504,32 @@ static ssize_t regmap_cache_bypass_write_file(struct file *file,
{
struct regmap *map = container_of(file->private_data,
struct regmap, cache_bypass);
- ssize_t result;
- bool was_enabled;
+ bool new_val;
+ int err;

- map->lock(map->lock_arg);
+ err = kstrtobool_from_user(user_buf, count, &new_val);
+ /* Ignore malforned data like debugfs_write_file_bool() */
+ if (err)
+ return count;

- was_enabled = map->cache_bypass;
+ err = debugfs_file_get(file->f_path.dentry);
+ if (err)
+ return err;

- result = debugfs_write_file_bool(file, user_buf, count, ppos);
- if (result < 0)
- goto out;
+ map->lock(map->lock_arg);

- if (map->cache_bypass && !was_enabled) {
+ if (new_val && !map->cache_bypass) {
dev_warn(map->dev, "debugfs cache_bypass=Y forced\n");
add_taint(TAINT_USER, LOCKDEP_STILL_OK);
- } else if (!map->cache_bypass && was_enabled) {
+ } else if (!new_val && map->cache_bypass) {
dev_warn(map->dev, "debugfs cache_bypass=N forced\n");
}
+ map->cache_bypass = new_val;

-out:
map->unlock(map->lock_arg);
+ debugfs_file_put(file->f_path.dentry);

- return result;
+ return count;
}

static const struct file_operations regmap_cache_bypass_fops = {
--
2.25.1


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