file: Rename __fcheck_files to files_lookup_fd_raw

[ Upstream commit bebf684bf330915e6c96313ad7db89a5480fc9c2 ]

The function fcheck despite it's comment is poorly named
as it has no callers that only check it's return value.
All of fcheck's callers use the returned file descriptor.
The same is true for fcheck_files and __fcheck_files.

A new less confusing name is needed.  In addition the names
of these functions are confusing as they do not report
the kind of locks that are needed to be held when these
functions are called making error prone to use them.

To remedy this I am making the base functio name lookup_fd
and will and prefixes and sufficies to indicate the rest
of the context.

Name the function (previously called __fcheck_files) that proceeds
from a struct files_struct, looks up the struct file of a file
descriptor, and requires it's callers to verify all of the appropriate
locks are held files_lookup_fd_raw.

The need for better names became apparent in the last round of
discussion of this set of changes[1].

[1] https://lkml.kernel.org/r/CAHk-=wj8BQbgJFLa+J0e=iT-1qpmCRTbPAJ8gd6MJQ=kbRPqyQ@mail.gmail.com
Link: https://lkml.kernel.org/r/20201120231441.29911-7-ebiederm@xmission.com
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
[ cel: adjusted to apply to v5.10.y ]
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/fs/file.c b/fs/file.c
index fea693acc065eb7e8cae518c30285e74cd18fcc1..eb1e2b7220ac6a26c5798f51d903f816b8714cde 100644 (file)
--- a/fs/file.c
+++ b/fs/file.c
@@ -866,7 +866,7 @@ loop:
                        file = NULL;
                else if (!get_file_rcu_many(file, refs))
                        goto loop;
-               else if (__fcheck_files(files, fd) != file) {
+               else if (files_lookup_fd_raw(files, fd) != file) {
                        fput_many(file, refs);
                        goto loop;
                }
@@ -933,7 +933,7 @@ static unsigned long __fget_light(unsigned int fd, fmode_t mask)
        struct file *file;
 
        if (atomic_read(&files->count) == 1) {
-               file = __fcheck_files(files, fd);
+               file = files_lookup_fd_raw(files, fd);
                if (!file || unlikely(file->f_mode & mask))
                        return 0;
                return (unsigned long)file;

diff --git a/include/linux/fdtable.h b/include/linux/fdtable.h
index c0ca6fb3f0f9568bb7496a5f4b3d3fd15847c344..10e75b4c30a43a77b0fce05af2f25ff385f4529a 100644 (file)
--- a/include/linux/fdtable.h
+++ b/include/linux/fdtable.h
@@ -80,7 +80,7 @@ struct dentry;
 /*
  * The caller must ensure that fd table isn't shared or hold rcu or file lock
  */
-static inline struct file *__fcheck_files(struct files_struct *files, unsigned int fd)
+static inline struct file *files_lookup_fd_raw(struct files_struct *files, unsigned int fd)
 {
        struct fdtable *fdt = rcu_dereference_raw(files->fdt);
 
@@ -96,7 +96,7 @@ static inline struct file *fcheck_files(struct files_struct *files, unsigned int
        RCU_LOCKDEP_WARN(!rcu_read_lock_held() &&
                           !lockdep_is_held(&files->file_lock),
                           "suspicious rcu_dereference_check() usage");
-       return __fcheck_files(files, fd);
+       return files_lookup_fd_raw(files, fd);
 }
 
 /*