fs: provide locked helper variant of close_fd_get_file()

Assumes current->files->file_lock is already held on invocation. Helps
the caller check the file before removing the fd, if it needs to.

Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/fs/file.c b/fs/file.c
index dab120b..f3a4bac 100644 (file)
--- a/fs/file.c
+++ b/fs/file.c
@@ -22,6 +22,8 @@
 #include <linux/close_range.h>
 #include <net/sock.h>
 
+#include "internal.h"
+
 unsigned int sysctl_nr_open __read_mostly = 1024*1024;
 unsigned int sysctl_nr_open_min = BITS_PER_LONG;
 /* our min() is unusable in constant expressions ;-/ */
@@ -732,36 +734,48 @@ int __close_range(unsigned fd, unsigned max_fd, unsigned int flags)
 }
 
 /*
- * variant of close_fd that gets a ref on the file for later fput.
- * The caller must ensure that filp_close() called on the file, and then
- * an fput().
+ * 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)
+int __close_fd_get_file(unsigned int fd, struct file **res)
 {
        struct files_struct *files = current->files;
        struct file *file;
        struct fdtable *fdt;
 
-       spin_lock(&files->file_lock);
        fdt = files_fdtable(files);
        if (fd >= fdt->max_fds)
-               goto out_unlock;
+               goto out_err;
        file = fdt->fd[fd];
        if (!file)
-               goto out_unlock;
+               goto out_err;
        rcu_assign_pointer(fdt->fd[fd], NULL);
        __put_unused_fd(files, fd);
-       spin_unlock(&files->file_lock);
        get_file(file);
        *res = file;
        return 0;
-
-out_unlock:
-       spin_unlock(&files->file_lock);
+out_err:
        *res = NULL;
        return -ENOENT;
 }
 
+/*
+ * variant of close_fd that gets a ref on the file for later fput.
+ * 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 files_struct *files = current->files;
+       int ret;
+
+       spin_lock(&files->file_lock);
+       ret = __close_fd_get_file(fd, res);
+       spin_unlock(&files->file_lock);
+
+       return ret;
+}
+
 void do_close_on_exec(struct files_struct *files)
 {
        unsigned i;

diff --git a/fs/internal.h b/fs/internal.h
index 77c50be..c6c85f6 100644 (file)
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -132,6 +132,7 @@ extern struct file *do_file_open_root(struct dentry *, struct vfsmount *,
                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);
 
 long do_sys_ftruncate(unsigned int fd, loff_t length, int small);
 int chmod_common(const struct path *path, umode_t mode);