Right now we have two places that do such removals - pick_file()
and {__,}close_fd_get_file().
They are almost identical - the only difference is in calling
conventions (well, and the fact that __... is called with descriptor
table locked).
Calling conventions are... interesting.
1) pick_file() - returns file or ERR_PTR(-EBADF) or ERR_PTR(-EINVAL).
The latter is for "descriptor is greater than size of descriptor table".
One of the callers treats all ERR_PTR(...) as "return -EBADF"; another
uses ERR_PTR(-EINVAL) as "end the loop now" indicator.
2) {__,}close_fd_get_file() returns 0 or -ENOENT (huh?), with file (or NULL)
passed to caller by way of struct file ** argument. One of the callers
(binder) ignores the return value completely and checks if the file is NULL.
Another (io_uring) checks for return value being negative, then maps
-ENOENT to -EBADF, not that any other value would be possible.
ERR_PTR(-EINVAL) magic in case of pick_file() is borderline defensible;
{__,}close_fd_get_file() conventions are insane. The older caller
(in binder) had never even looked at return value; the newer one
patches the bogus -ENOENT to what it wants to report, with strange
"defensive" BS logics just in case __close_fd_get_file() would somehow
find a different error to report.
At the very least, {__,}close_fd_get_file() callers would've been happier
if it just returned file or NULL. What's more, I'm seriously tempted
to make pick_file() do the same thing. close_fd() won't care (checking
for NULL is just as easy as for IS_ERR) and __range_close() could just
as well cap the max_fd argument with last_fd(files_fdtable(current->files)).
Does anybody see problems with the following?
commit 8819510a641800a63ab10d6b5ab283cada1cbd50
Author: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Date: Thu May 12 17:08:03 2022 -0400
Unify the primitives for file descriptor closing
Currently we have 3 primitives for removing an opened file from descriptor
table - pick_file(), __close_fd_get_file() and close_fd_get_file(). Their
calling conventions are rather odd and there's a code duplication for no
good reason. They can be unified -
1) have __range_close() cap max_fd in the very beginning; that way
we don't need separate way for pick_file() to report being past the end
of descriptor table.
2) make {__,}close_fd_get_file() return file (or NULL) directly, rather
than returning it via struct file ** argument. Don't bother with
(bogus) return value - nobody wants that -ENOENT.
3) make pick_file() return NULL on unopened descriptor - the only caller
that used to care about the distinction between descriptor past the end
of descriptor table and finding NULL in descriptor table doesn't give
a damn after (1).
4) lift ->files_lock out of pick_file()
That actually simplifies the callers, as well as the primitives themselves.
Code duplication is also gone...
Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index 8351c5638880..27c9b004823a 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -1855,7 +1855,7 @@ static void binder_deferred_fd_close(int fd)
if (!twcb)
return;
init_task_work(&twcb->twork, binder_do_fd_close);
- close_fd_get_file(fd, &twcb->file);
+ twcb->file = close_fd_get_file(fd);
if (twcb->file) {
filp_close(twcb->file, current->files);
task_work_add(current, &twcb->twork, TWA_RESUME);
diff --git a/fs/file.c b/fs/file.c
index ee9317346702..9780888fa2da 100644
--- a/fs/file.c
+++ b/fs/file.c
@@ -630,32 +630,21 @@ EXPORT_SYMBOL(fd_install);
* @files: file struct to retrieve file from
* @fd: file descriptor to retrieve file for
*
- * If this functions returns an EINVAL error pointer the fd was beyond the
- * current maximum number of file descriptors for that fdtable.
- *
- * Returns: The file associated with @fd, on error returns an error pointer.
+ * Returns: The file associated with @fd (NULL if @fd is not open)
*/
static struct file *pick_file(struct files_struct *files, unsigned fd)
{
+ struct fdtable *fdt = files_fdtable(files);
struct file *file;
- struct fdtable *fdt;
- spin_lock(&files->file_lock);
- fdt = files_fdtable(files);
- if (fd >= fdt->max_fds) {
- file = ERR_PTR(-EINVAL);
- goto out_unlock;
- }
+ if (fd >= fdt->max_fds)
+ return NULL;
+
file = fdt->fd[fd];
- if (!file) {
- file = ERR_PTR(-EBADF);
- goto out_unlock;
+ if (file) {
+ rcu_assign_pointer(fdt->fd[fd], NULL);
+ __put_unused_fd(files, fd);
}
- rcu_assign_pointer(fdt->fd[fd], NULL);
- __put_unused_fd(files, fd);
-
-out_unlock:
- spin_unlock(&files->file_lock);
return file;
}
@@ -664,8 +653,10 @@ int close_fd(unsigned fd)
struct files_struct *files = current->files;
struct file *file;
+ spin_lock(&files->file_lock);
file = pick_file(files, fd);
- if (IS_ERR(file))
+ spin_unlock(&files->file_lock);
+ if (!file)
return -EBADF;
return filp_close(file, files);
@@ -702,20 +693,25 @@ static inline void __range_cloexec(struct files_struct *cur_fds,
static inline void __range_close(struct files_struct *cur_fds, unsigned int fd,
unsigned int max_fd)
{
+ unsigned n;
+
+ rcu_read_lock();
+ n = last_fd(files_fdtable(cur_fds));
+ rcu_read_unlock();
+ max_fd = min(max_fd, n);
+
while (fd <= max_fd) {
struct file *file;
+ spin_lock(&cur_fds->file_lock);
file = pick_file(cur_fds, fd++);
- if (!IS_ERR(file)) {
+ spin_unlock(&cur_fds->file_lock);
+
+ if (file) {
/* found a valid file to close */
filp_close(file, cur_fds);
cond_resched();
- continue;
}
-
- /* beyond the last fd in that table */
- if (PTR_ERR(file) == -EINVAL)
- return;
}
}
@@ -795,26 +791,9 @@ int __close_range(unsigned fd, unsigned max_fd, unsigned int flags)
* See close_fd_get_file() below, this variant assumes current->files->file_lock
* is held.
*/
-int __close_fd_get_file(unsigned int fd, struct file **res)
+struct file *__close_fd_get_file(unsigned int fd)
{
- struct files_struct *files = current->files;
- struct file *file;
- struct fdtable *fdt;
-
- fdt = files_fdtable(files);
- if (fd >= fdt->max_fds)
- goto out_err;
- file = fdt->fd[fd];
- if (!file)
- goto out_err;
- rcu_assign_pointer(fdt->fd[fd], NULL);
- __put_unused_fd(files, fd);
- get_file(file);
- *res = file;
- return 0;
-out_err:
- *res = NULL;
- return -ENOENT;
+ return pick_file(current->files, fd);
}
/*
@@ -822,16 +801,16 @@ int __close_fd_get_file(unsigned int fd, struct file **res)
* The caller must ensure that filp_close() called on the file, and then
* an fput().
*/
-int close_fd_get_file(unsigned int fd, struct file **res)
+struct file *close_fd_get_file(unsigned int fd)
{
struct files_struct *files = current->files;
- int ret;
+ struct file *file;
spin_lock(&files->file_lock);
- ret = __close_fd_get_file(fd, res);
+ file = pick_file(files, fd);
spin_unlock(&files->file_lock);
- return ret;
+ return file;
}
void do_close_on_exec(struct files_struct *files)
diff --git a/fs/internal.h b/fs/internal.h
index 08503dc68d2b..4065e2679103 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -125,7 +125,7 @@ extern struct file *do_file_open_root(const struct path *,
const char *, const struct open_flags *);
extern struct open_how build_open_how(int flags, umode_t mode);
extern int build_open_flags(const struct open_how *how, struct open_flags *op);
-extern int __close_fd_get_file(unsigned int fd, struct file **res);
+extern struct file *__close_fd_get_file(unsigned int fd);
long do_sys_ftruncate(unsigned int fd, loff_t length, int small);
int chmod_common(const struct path *path, umode_t mode);
diff --git a/fs/io_uring.c b/fs/io_uring.c
index dc580a30723d..7257b0870353 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -5137,13 +5137,10 @@ static int io_close(struct io_kiocb *req, unsigned int issue_flags)
return -EAGAIN;
}
- ret = __close_fd_get_file(close->fd, &file);
+ file = __close_fd_get_file(close->fd);
spin_unlock(&files->file_lock);
- if (ret < 0) {
- if (ret == -ENOENT)
- ret = -EBADF;
+ if (!file)
goto err;
- }
/* No ->flush() or already async, safely close from here */
ret = filp_close(file, current->files);
diff --git a/include/linux/fdtable.h b/include/linux/fdtable.h
index d0e78174874a..e066816f3519 100644
--- a/include/linux/fdtable.h
+++ b/include/linux/fdtable.h
@@ -125,7 +125,7 @@ int iterate_fd(struct files_struct *, unsigned,
extern int close_fd(unsigned int fd);
extern int __close_range(unsigned int fd, unsigned int max_fd, unsigned int flags);
-extern int close_fd_get_file(unsigned int fd, struct file **res);
+extern struct file *close_fd_get_file(unsigned int fd);
extern int unshare_fd(unsigned long unshare_flags, unsigned int max_fds,
struct files_struct **new_fdp);
