[PATCH 04/39] add struct fd constructors, get rid of __to_fd()

viro
2024-07-30T05:14:50Z

From: Al Viro <viro@zeniv.linux.org.uk>

Make __fdget() et.al. return struct fd directly.
New helpers: BORROWED_FD(file) and CLONED_FD(file), for
borrowed and cloned file references resp.

NOTE: this might need tuning; in particular, inline on
__fget_light() is there to keep the code generation same as
before - we probably want to keep it inlined in fdget() et.al.
(especially so in fdget_pos()), but that needs profiling.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
fs/file.c | 26 +++++++++++++-------------
include/linux/file.h | 33 +++++++++++----------------------
2 files changed, 24 insertions(+), 35 deletions(-)

diff --git a/fs/file.c b/fs/file.c
index a3b72aa64f11..6f5ed4daafd2 100644
--- a/fs/file.c
+++ b/fs/file.c
@@ -1128,7 +1128,7 @@ EXPORT_SYMBOL(task_lookup_next_fdget_rcu);
* The fput_needed flag returned by fget_light should be passed to the
* corresponding fput_light.
*/
-static unsigned long __fget_light(unsigned int fd, fmode_t mask)
+static inline struct fd __fget_light(unsigned int fd, fmode_t mask)
{
struct files_struct *files = current->files;
struct file *file;
@@ -1145,22 +1145,22 @@ static unsigned long __fget_light(unsigned int fd, fmode_t mask)
if (likely(atomic_read_acquire(&files->count) == 1)) {
file = files_lookup_fd_raw(files, fd);
if (!file || unlikely(file->f_mode & mask))
- return 0;
- return (unsigned long)file;
+ return EMPTY_FD;
+ return BORROWED_FD(file);
} else {
file = __fget_files(files, fd, mask);
if (!file)
- return 0;
- return FDPUT_FPUT | (unsigned long)file;
+ return EMPTY_FD;
+ return CLONED_FD(file);
}
}
-unsigned long __fdget(unsigned int fd)
+struct fd fdget(unsigned int fd)
{
return __fget_light(fd, FMODE_PATH);
}
-EXPORT_SYMBOL(__fdget);
+EXPORT_SYMBOL(fdget);

-unsigned long __fdget_raw(unsigned int fd)
+struct fd fdget_raw(unsigned int fd)
{
return __fget_light(fd, 0);
}
@@ -1181,16 +1181,16 @@ static inline bool file_needs_f_pos_lock(struct file *file)
(file_count(file) > 1 || file->f_op->iterate_shared);
}

-unsigned long __fdget_pos(unsigned int fd)
+struct fd fdget_pos(unsigned int fd)
{
- unsigned long v = __fdget(fd);
- struct file *file = (struct file *)(v & ~3);
+ struct fd f = fdget(fd);
+ struct file *file = fd_file(f);

if (file && file_needs_f_pos_lock(file)) {
- v |= FDPUT_POS_UNLOCK;
+ f.word |= FDPUT_POS_UNLOCK;
mutex_lock(&file->f_pos_lock);
}
- return v;
+ return f;
}

void __f_unlock_pos(struct file *f)
diff --git a/include/linux/file.h b/include/linux/file.h
index bdd6e1766839..00a42604d322 100644
--- a/include/linux/file.h
+++ b/include/linux/file.h
@@ -53,6 +53,14 @@ static inline bool fd_empty(struct fd f)
}

#define EMPTY_FD (struct fd){0}
+static inline struct fd BORROWED_FD(struct file *f)
+{
+ return (struct fd){(unsigned long)f};
+}
+static inline struct fd CLONED_FD(struct file *f)
+{
+ return (struct fd){(unsigned long)f | FDPUT_FPUT};
+}

static inline void fdput(struct fd fd)
{
@@ -63,30 +71,11 @@ static inline void fdput(struct fd fd)
extern struct file *fget(unsigned int fd);
extern struct file *fget_raw(unsigned int fd);
extern struct file *fget_task(struct task_struct *task, unsigned int fd);
-extern unsigned long __fdget(unsigned int fd);
-extern unsigned long __fdget_raw(unsigned int fd);
-extern unsigned long __fdget_pos(unsigned int fd);
extern void __f_unlock_pos(struct file *);

-static inline struct fd __to_fd(unsigned long v)
-{
- return (struct fd){v};
-}
-
-static inline struct fd fdget(unsigned int fd)
-{
- return __to_fd(__fdget(fd));
-}
-
-static inline struct fd fdget_raw(unsigned int fd)
-{
- return __to_fd(__fdget_raw(fd));
-}
-
-static inline struct fd fdget_pos(int fd)
-{
- return __to_fd(__fdget_pos(fd));
-}
+struct fd fdget(unsigned int fd);
+struct fd fdget_raw(unsigned int fd);
+struct fd fdget_pos(unsigned int fd);

static inline void fdput_pos(struct fd f)
{
--
2.39.2