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-rw-r--r--fs/kernfs/file.c73
1 files changed, 50 insertions, 23 deletions
diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c
index 4429d6d9217f..697390ea47b8 100644
--- a/fs/kernfs/file.c
+++ b/fs/kernfs/file.c
@@ -106,7 +106,7 @@ static void *kernfs_seq_start(struct seq_file *sf, loff_t *ppos)
const struct kernfs_ops *ops;
/*
- * @of->mutex nests outside active ref and is just to ensure that
+ * @of->mutex nests outside active ref and is primarily to ensure that
* the ops aren't called concurrently for the same open file.
*/
mutex_lock(&of->mutex);
@@ -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 just 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;
}
@@ -278,19 +282,16 @@ static ssize_t kernfs_fop_write(struct file *file, const char __user *user_buf,
len = min_t(size_t, count, PAGE_SIZE);
}
- buf = kmalloc(len + 1, GFP_KERNEL);
+ buf = of->prealloc_buf;
+ if (!buf)
+ buf = kmalloc(len + 1, GFP_KERNEL);
if (!buf)
return -ENOMEM;
- if (copy_from_user(buf, user_buf, len)) {
- len = -EFAULT;
- goto out_free;
- }
- buf[len] = '\0'; /* guarantee string termination */
-
/*
- * @of->mutex nests outside active ref and is just 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)) {
@@ -299,19 +300,27 @@ static ssize_t kernfs_fop_write(struct file *file, const char __user *user_buf,
goto out_free;
}
+ if (copy_from_user(buf, user_buf, len)) {
+ len = -EFAULT;
+ goto out_unlock;
+ }
+ buf[len] = '\0'; /* guarantee string termination */
+
ops = kernfs_ops(of->kn);
if (ops->write)
len = ops->write(of, buf, len, *ppos);
else
len = -EINVAL;
- kernfs_put_active(of->kn);
- mutex_unlock(&of->mutex);
-
if (len > 0)
*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;
}
@@ -685,6 +694,22 @@ 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);
+ error = -ENOMEM;
+ if (!of->prealloc_buf)
+ goto err_free;
+ }
+
/*
* Always instantiate seq_file even if read access doesn't use
* seq_file or is not requested. This unifies private data access
@@ -715,6 +740,7 @@ static int kernfs_fop_open(struct inode *inode, struct file *file)
err_close:
seq_release(inode, file);
err_free:
+ kfree(of->prealloc_buf);
kfree(of);
err_out:
kernfs_put_active(kn);
@@ -728,6 +754,7 @@ static int kernfs_fop_release(struct inode *inode, struct file *filp)
kernfs_put_open_node(kn, of);
seq_release(inode, filp);
+ kfree(of->prealloc_buf);
kfree(of);
return 0;