fs: Preserve error code in get_empty_filp(), part 2

Allocating a file structure in function get_empty_filp() might fail because
of several reasons:
 - not enough memory for file structures
 - operation is not allowed
 - user is over its limit

Currently the function returns NULL in all cases and we loose the exact
reason of the error. All callers of get_empty_filp() assume that the function
can fail with ENFILE only.

Return error through pointer. Change all callers to preserve this error code.

[AV: cleaned up a bit, carved the get_empty_filp() part out into a separate commit
(things remaining here deal with alloc_file()), removed pipe(2) behaviour change]

Signed-off-by: Anatol Pomozov <anatol.pomozov@gmail.com>
Reviewed-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

4 files changed, 11 insertions, 15 deletions

diff --git a/fs/anon_inodes.c b/fs/anon_inodes.c
index 28d39fb84ae3..a14eb0c1cd8c 100644
--- a/fs/anon_inodes.c
+++ b/fs/anon_inodes.c
@@ -131,7 +131,6 @@ struct file *anon_inode_getfile(const char *name,
         struct qstr this;
         struct path path;
         struct file *file;
-        int error;
 
         if (IS_ERR(anon_inode_inode))
                 return ERR_PTR(-ENODEV);
@@ -143,7 +142,7 @@ struct file *anon_inode_getfile(const char *name,
          * Link the inode to a directory entry by creating a unique name
          * using the inode sequence number.
          */
-        error = -ENOMEM;
+        file = ERR_PTR(-ENOMEM);
         this.name = name;
         this.len = strlen(name);
         this.hash = 0;
@@ -160,9 +159,8 @@ struct file *anon_inode_getfile(const char *name,
 
         d_instantiate(path.dentry, anon_inode_inode);
 
-        error = -ENFILE;
         file = alloc_file(&path, OPEN_FMODE(flags), fops);
-        if (!file)
+        if (IS_ERR(file))
                 goto err_dput;
         file->f_mapping = anon_inode_inode->i_mapping;
 
@@ -177,7 +175,7 @@ err_dput:
         path_put(&path);
 err_module:
         module_put(fops->owner);
-        return ERR_PTR(error);
+        return file;
 }
 EXPORT_SYMBOL_GPL(anon_inode_getfile);
 
diff --git a/fs/file_table.c b/fs/file_table.c
index cd76d4fdf4a4..aa07d3684a2e 100644
--- a/fs/file_table.c
+++ b/fs/file_table.c
@@ -173,7 +173,7 @@ struct file *alloc_file(struct path *path, fmode_t mode,
 
         file = get_empty_filp();
         if (IS_ERR(file))
-                return NULL;
+                return file;
 
         file->f_path = *path;
         file->f_mapping = path->dentry->d_inode->i_mapping;
diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index edb42ea60c76..99fe7ef2f09b 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -923,8 +923,7 @@ struct file *hugetlb_file_setup(const char *name, unsigned long addr,
                                 struct user_struct **user,
                                 int creat_flags, int page_size_log)
 {
-        int error = -ENOMEM;
-        struct file *file;
+        struct file *file = ERR_PTR(-ENOMEM);
         struct inode *inode;
         struct path path;
         struct dentry *root;
@@ -964,7 +963,7 @@ struct file *hugetlb_file_setup(const char *name, unsigned long addr,
                 goto out_shm_unlock;
 
         path.mnt = mntget(hugetlbfs_vfsmount[hstate_idx]);
-        error = -ENOSPC;
+        file = ERR_PTR(-ENOSPC);
         inode = hugetlbfs_get_inode(root->d_sb, NULL, S_IFREG | S_IRWXUGO, 0);
         if (!inode)
                 goto out_dentry;
@@ -973,7 +972,7 @@ struct file *hugetlb_file_setup(const char *name, unsigned long addr,
         size += addr & ~huge_page_mask(hstate);
         num_pages = ALIGN(size, huge_page_size(hstate)) >>
                         huge_page_shift(hstate);
-        error = -ENOMEM;
+        file = ERR_PTR(-ENOMEM);
         if (hugetlb_reserve_pages(inode, 0, num_pages, NULL, acctflag))
                 goto out_inode;
 
@@ -981,10 +980,9 @@ struct file *hugetlb_file_setup(const char *name, unsigned long addr,
         inode->i_size = size;
         clear_nlink(inode);
 
-        error = -ENFILE;
         file = alloc_file(&path, FMODE_WRITE | FMODE_READ,
                         &hugetlbfs_file_operations);
-        if (!file)
+        if (IS_ERR(file))
                 goto out_dentry; /* inode is already attached */
 
         return file;
@@ -998,7 +996,7 @@ out_shm_unlock:
                 user_shm_unlock(size, *user);
                 *user = NULL;
         }
-        return ERR_PTR(error);
+        return file;
 }
 
 static int __init init_hugetlbfs_fs(void)
diff --git a/fs/pipe.c b/fs/pipe.c
index 39baf6c3ebb0..64a494cef0a0 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -1037,13 +1037,13 @@ int create_pipe_files(struct file **res, int flags)
 
         err = -ENFILE;
         f = alloc_file(&path, FMODE_WRITE, &write_pipefifo_fops);
-        if (!f)
+        if (IS_ERR(f))
                 goto err_dentry;
 
         f->f_flags = O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT));
 
         res[0] = alloc_file(&path, FMODE_READ, &read_pipefifo_fops);
-        if (!res[0])
+        if (IS_ERR(res[0]))
                 goto err_file;
 
         path_get(&path);