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Diffstat (limited to 'fs/kernfs')
-rw-r--r--fs/kernfs/file.c30
1 files changed, 21 insertions, 9 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);