1 files changed, 16 insertions, 6 deletions

diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c
index dbf397bfdff2..8034706a7af8 100644
--- a/fs/kernfs/file.c
+++ b/fs/kernfs/file.c
@@ -252,10 +252,18 @@ static ssize_t kernfs_fop_write(struct file *file, const char __user *user_buf,
                                 size_t count, loff_t *ppos)
 {
         struct kernfs_open_file *of = kernfs_of(file);
-        ssize_t len = min_t(size_t, count, PAGE_SIZE);
         const struct kernfs_ops *ops;
+        size_t len;
         char *buf;
 
+        if (of->atomic_write_len) {
+                len = count;
+                if (len > of->atomic_write_len)
+                        return -E2BIG;
+        } else {
+                len = min_t(size_t, count, PAGE_SIZE);
+        }
+
         buf = kmalloc(len + 1, GFP_KERNEL);
         if (!buf)
                 return -ENOMEM;
@@ -653,6 +661,12 @@ static int kernfs_fop_open(struct inode *inode, struct file *file)
         of->file = file;
 
         /*
+         * Write path needs to atomic_write_len outside active reference.
+         * Cache it in open_file.  See kernfs_fop_write() for details.
+         */
+        of->atomic_write_len = ops->atomic_write_len;
+
+        /*
          * Always instantiate seq_file even if read access doesn't use
          * seq_file or is not requested.  This unifies private data access
          * and readable regular files are the vast majority anyway.
@@ -820,7 +834,6 @@ struct kernfs_node *__kernfs_create_file(struct kernfs_node *parent,
                                          bool name_is_static,
                                          struct lock_class_key *key)
 {
-        struct kernfs_addrm_cxt acxt;
         struct kernfs_node *kn;
         unsigned flags;
         int rc;
@@ -855,10 +868,7 @@ struct kernfs_node *__kernfs_create_file(struct kernfs_node *parent,
         if (ops->mmap)
                 kn->flags |= KERNFS_HAS_MMAP;
 
-        kernfs_addrm_start(&acxt);
-        rc = kernfs_add_one(&acxt, kn);
-        kernfs_addrm_finish(&acxt);
-
+        rc = kernfs_add_one(kn);
         if (rc) {
                 kernfs_put(kn);
                 return ERR_PTR(rc);