[PATCH] merge locate_fd() and get_unused_fd()

	New primitive: alloc_fd(start, flags).  get_unused_fd() and
get_unused_fd_flags() become wrappers on top of it.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

3 files changed, 75 insertions, 129 deletions

diff --git a/fs/fcntl.c b/fs/fcntl.c
index 61d625136813..2e40799daad6 100644
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -49,73 +49,6 @@ static int get_close_on_exec(unsigned int fd)
         return res;
 }
 
-/*
- * locate_fd finds a free file descriptor in the open_fds fdset,
- * expanding the fd arrays if necessary.  Must be called with the
- * file_lock held for write.
- */
-
-static int locate_fd(unsigned int orig_start, int cloexec)
-{
-        struct files_struct *files = current->files;
-        unsigned int newfd;
-        unsigned int start;
-        int error;
-        struct fdtable *fdt;
-
-        spin_lock(&files->file_lock);
-repeat:
-        fdt = files_fdtable(files);
-        /*
-         * Someone might have closed fd's in the range
-         * orig_start..fdt->next_fd
-         */
-        start = orig_start;
-        if (start < files->next_fd)
-                start = files->next_fd;
-
-        newfd = start;
-        if (start < fdt->max_fds)
-                newfd = find_next_zero_bit(fdt->open_fds->fds_bits,
-                                           fdt->max_fds, start);
-
-        error = expand_files(files, newfd);
-        if (error < 0)
-                goto out;
-
-        /*
-         * If we needed to expand the fs array we
-         * might have blocked - try again.
-         */
-        if (error)
-                goto repeat;
-
-        if (start <= files->next_fd)
-                files->next_fd = newfd + 1;
-
-        FD_SET(newfd, fdt->open_fds);
-        if (cloexec)
-                FD_SET(newfd, fdt->close_on_exec);
-        else
-                FD_CLR(newfd, fdt->close_on_exec);
-        error = newfd;
-
-out:
-        spin_unlock(&files->file_lock);
-        return error;
-}
-
-static int dupfd(struct file *file, unsigned int start, int cloexec)
-{
-        int fd = locate_fd(start, cloexec);
-        if (fd >= 0)
-                fd_install(fd, file);
-        else
-                fput(file);
-
-        return fd;
-}
-
 asmlinkage long sys_dup3(unsigned int oldfd, unsigned int newfd, int flags)
 {
         int err = -EBADF;
@@ -194,10 +127,15 @@ asmlinkage long sys_dup2(unsigned int oldfd, unsigned int newfd)
 asmlinkage long sys_dup(unsigned int fildes)
 {
         int ret = -EBADF;
-        struct file * file = fget(fildes);
-
-        if (file)
-                ret = dupfd(file, 0, 0);
+        struct file *file = fget(fildes);
+
+        if (file) {
+                ret = get_unused_fd();
+                if (ret >= 0)
+                        fd_install(ret, file);
+                else
+                        fput(file);
+        }
         return ret;
 }
 
@@ -322,8 +260,11 @@ static long do_fcntl(int fd, unsigned int cmd, unsigned long arg,
         case F_DUPFD_CLOEXEC:
                 if (arg >= current->signal->rlim[RLIMIT_NOFILE].rlim_cur)
                         break;
-                get_file(filp);
-                err = dupfd(filp, arg, cmd == F_DUPFD_CLOEXEC);
+                err = alloc_fd(arg, cmd == F_DUPFD_CLOEXEC ? O_CLOEXEC : 0);
+                if (err >= 0) {
+                        get_file(filp);
+                        fd_install(err, filp);
+                }
                 break;
         case F_GETFD:
                 err = get_close_on_exec(fd) ? FD_CLOEXEC : 0;
diff --git a/fs/file.c b/fs/file.c
index d8773b19fe47..f313314f996f 100644
--- a/fs/file.c
+++ b/fs/file.c
@@ -6,6 +6,7 @@
  *  Manage the dynamic fd arrays in the process files_struct.
  */
 
+#include <linux/module.h>
 #include <linux/fs.h>
 #include <linux/mm.h>
 #include <linux/time.h>
@@ -432,3 +433,63 @@ struct files_struct init_files = {
         },
         .file_lock      = __SPIN_LOCK_UNLOCKED(init_task.file_lock),
 };
+
+/*
+ * allocate a file descriptor, mark it busy.
+ */
+int alloc_fd(unsigned start, unsigned flags)
+{
+        struct files_struct *files = current->files;
+        unsigned int fd;
+        int error;
+        struct fdtable *fdt;
+
+        spin_lock(&files->file_lock);
+repeat:
+        fdt = files_fdtable(files);
+        fd = start;
+        if (fd < files->next_fd)
+                fd = files->next_fd;
+
+        if (fd < fdt->max_fds)
+                fd = find_next_zero_bit(fdt->open_fds->fds_bits,
+                                           fdt->max_fds, fd);
+
+        error = expand_files(files, fd);
+        if (error < 0)
+                goto out;
+
+        /*
+         * If we needed to expand the fs array we
+         * might have blocked - try again.
+         */
+        if (error)
+                goto repeat;
+
+        if (start <= files->next_fd)
+                files->next_fd = fd + 1;
+
+        FD_SET(fd, fdt->open_fds);
+        if (flags & O_CLOEXEC)
+                FD_SET(fd, fdt->close_on_exec);
+        else
+                FD_CLR(fd, fdt->close_on_exec);
+        error = fd;
+#if 1
+        /* Sanity check */
+        if (rcu_dereference(fdt->fd[fd]) != NULL) {
+                printk(KERN_WARNING "alloc_fd: slot %d not NULL!\n", fd);
+                rcu_assign_pointer(fdt->fd[fd], NULL);
+        }
+#endif
+
+out:
+        spin_unlock(&files->file_lock);
+        return error;
+}
+
+int get_unused_fd(void)
+{
+        return alloc_fd(0, 0);
+}
+EXPORT_SYMBOL(get_unused_fd);
diff --git a/fs/open.c b/fs/open.c
index 52647be277a2..07da9359481c 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -963,62 +963,6 @@ struct file *dentry_open(struct dentry *dentry, struct vfsmount *mnt, int flags)
 }
 EXPORT_SYMBOL(dentry_open);
 
-/*
- * Find an empty file descriptor entry, and mark it busy.
- */
-int get_unused_fd_flags(int flags)
-{
-        struct files_struct * files = current->files;
-        int fd, error;
-        struct fdtable *fdt;
-
-        spin_lock(&files->file_lock);
-
-repeat:
-        fdt = files_fdtable(files);
-        fd = find_next_zero_bit(fdt->open_fds->fds_bits, fdt->max_fds,
-                                files->next_fd);
-
-        /* Do we need to expand the fd array or fd set?  */
-        error = expand_files(files, fd);
-        if (error < 0)
-                goto out;
-
-        if (error) {
-                /*
-                 * If we needed to expand the fs array we
-                 * might have blocked - try again.
-                 */
-                goto repeat;
-        }
-
-        FD_SET(fd, fdt->open_fds);
-        if (flags & O_CLOEXEC)
-                FD_SET(fd, fdt->close_on_exec);
-        else
-                FD_CLR(fd, fdt->close_on_exec);
-        files->next_fd = fd + 1;
-#if 1
-        /* Sanity check */
-        if (fdt->fd[fd] != NULL) {
-                printk(KERN_WARNING "get_unused_fd: slot %d not NULL!\n", fd);
-                fdt->fd[fd] = NULL;
-        }
-#endif
-        error = fd;
-
-out:
-        spin_unlock(&files->file_lock);
-        return error;
-}
-
-int get_unused_fd(void)
-{
-        return get_unused_fd_flags(0);
-}
-
-EXPORT_SYMBOL(get_unused_fd);
-
 static void __put_unused_fd(struct files_struct *files, unsigned int fd)
 {
         struct fdtable *fdt = files_fdtable(files);