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-rw-r--r--fs/kernfs/file.c30
-rw-r--r--fs/sysfs/file.c32
2 files changed, 49 insertions, 13 deletions
diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c
index 70186e2e692a..697390ea47b8 100644
--- a/fs/kernfs/file.c
+++ b/fs/kernfs/file.c
@@ -189,13 +189,16 @@ static ssize_t kernfs_file_direct_read(struct kernfs_open_file *of,
const struct kernfs_ops *ops;
char *buf;
- buf = kmalloc(len, GFP_KERNEL);
+ buf = of->prealloc_buf;
+ if (!buf)
+ buf = kmalloc(len, GFP_KERNEL);
if (!buf)
return -ENOMEM;
/*
- * @of->mutex nests outside active ref and is primarily to ensure that
- * the ops aren't called concurrently for the same open file.
+ * @of->mutex nests outside active ref and is used both to ensure that
+ * the ops aren't called concurrently for the same open file, and
+ * to provide exclusive access to ->prealloc_buf (when that exists).
*/
mutex_lock(&of->mutex);
if (!kernfs_get_active(of->kn)) {
@@ -210,21 +213,22 @@ static ssize_t kernfs_file_direct_read(struct kernfs_open_file *of,
else
len = -EINVAL;
- kernfs_put_active(of->kn);
- mutex_unlock(&of->mutex);
-
if (len < 0)
- goto out_free;
+ goto out_unlock;
if (copy_to_user(user_buf, buf, len)) {
len = -EFAULT;
- goto out_free;
+ goto out_unlock;
}
*ppos += len;
+ out_unlock:
+ kernfs_put_active(of->kn);
+ mutex_unlock(&of->mutex);
out_free:
- kfree(buf);
+ if (buf != of->prealloc_buf)
+ kfree(buf);
return len;
}
@@ -690,6 +694,14 @@ static int kernfs_fop_open(struct inode *inode, struct file *file)
*/
of->atomic_write_len = ops->atomic_write_len;
+ error = -EINVAL;
+ /*
+ * ->seq_show is incompatible with ->prealloc,
+ * as seq_read does its own allocation.
+ * ->read must be used instead.
+ */
+ if (ops->prealloc && ops->seq_show)
+ goto err_free;
if (ops->prealloc) {
int len = of->atomic_write_len ?: PAGE_SIZE;
of->prealloc_buf = kmalloc(len + 1, GFP_KERNEL);
diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
index 4ad3721a991c..dfe928a9540f 100644
--- a/fs/sysfs/file.c
+++ b/fs/sysfs/file.c
@@ -102,6 +102,22 @@ static ssize_t sysfs_kf_bin_read(struct kernfs_open_file *of, char *buf,
return battr->read(of->file, kobj, battr, buf, pos, count);
}
+/* kernfs read callback for regular sysfs files with pre-alloc */
+static ssize_t sysfs_kf_read(struct kernfs_open_file *of, char *buf,
+ size_t count, loff_t pos)
+{
+ const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
+ struct kobject *kobj = of->kn->parent->priv;
+
+ /*
+ * If buf != of->prealloc_buf, we don't know how
+ * large it is, so cannot safely pass it to ->show
+ */
+ if (pos || WARN_ON_ONCE(buf != of->prealloc_buf))
+ return 0;
+ return ops->show(kobj, of->kn->priv, buf);
+}
+
/* kernfs write callback for regular sysfs files */
static ssize_t sysfs_kf_write(struct kernfs_open_file *of, char *buf,
size_t count, loff_t pos)
@@ -184,13 +200,18 @@ static const struct kernfs_ops sysfs_file_kfops_rw = {
.write = sysfs_kf_write,
};
+static const struct kernfs_ops sysfs_prealloc_kfops_ro = {
+ .read = sysfs_kf_read,
+ .prealloc = true,
+};
+
static const struct kernfs_ops sysfs_prealloc_kfops_wo = {
.write = sysfs_kf_write,
.prealloc = true,
};
static const struct kernfs_ops sysfs_prealloc_kfops_rw = {
- .seq_show = sysfs_kf_seq_show,
+ .read = sysfs_kf_read,
.write = sysfs_kf_write,
.prealloc = true,
};
@@ -238,9 +259,12 @@ int sysfs_add_file_mode_ns(struct kernfs_node *parent,
ops = &sysfs_prealloc_kfops_rw;
else
ops = &sysfs_file_kfops_rw;
- } else if (sysfs_ops->show)
- ops = &sysfs_file_kfops_ro;
- else if (sysfs_ops->store) {
+ } else if (sysfs_ops->show) {
+ if (mode & SYSFS_PREALLOC)
+ ops = &sysfs_prealloc_kfops_ro;
+ else
+ ops = &sysfs_file_kfops_ro;
+ } else if (sysfs_ops->store) {
if (mode & SYSFS_PREALLOC)
ops = &sysfs_prealloc_kfops_wo;
else