[PATCH] Clean up expand_fdtable() and expand_files()

Perform a code cleanup against the expand_fdtable() and expand_files()
functions inside fs/file.c.  It aims to make the flow of code within these
functions simpler and easier to understand, via added comments and modest
refactoring.

Signed-off-by: Vadim Lobanov <vlobanov@speakeasy.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 35 insertions, 41 deletions

diff --git a/fs/file.c b/fs/file.c
index 8d3bfca7714b..2a991ac8e562 100644
--- a/fs/file.c
+++ b/fs/file.c
@@ -288,71 +288,65 @@ out:
 }
 
 /*
- * Expands the file descriptor table - it will allocate a new fdtable and
- * both fd array and fdset. It is expected to be called with the
- * files_lock held.
+ * Expand the file descriptor table.
+ * This function will allocate a new fdtable and both fd array and fdset, of
+ * the given size.
+ * Return <0 error code on error; 1 on successful completion.
+ * The files->file_lock should be held on entry, and will be held on exit.
  */
 static int expand_fdtable(struct files_struct *files, int nr)
         __releases(files->file_lock)
         __acquires(files->file_lock)
 {
-        int error = 0;
-        struct fdtable *fdt;
-        struct fdtable *nfdt = NULL;
+        struct fdtable *new_fdt, *cur_fdt;
 
         spin_unlock(&files->file_lock);
-        nfdt = alloc_fdtable(nr);
-        if (!nfdt) {
-                error = -ENOMEM;
-                spin_lock(&files->file_lock);
-                goto out;
-        }
-
+        new_fdt = alloc_fdtable(nr);
         spin_lock(&files->file_lock);
-        fdt = files_fdtable(files);
+        if (!new_fdt)
+                return -ENOMEM;
         /*
-         * Check again since another task may have expanded the
-         * fd table while we dropped the lock
+         * Check again since another task may have expanded the fd table while
+         * we dropped the lock
          */
-        if (nr >= fdt->max_fds || nr >= fdt->max_fdset) {
-                copy_fdtable(nfdt, fdt);
+        cur_fdt = files_fdtable(files);
+        if (nr >= cur_fdt->max_fds || nr >= cur_fdt->max_fdset) {
+                /* Continue as planned */
+                copy_fdtable(new_fdt, cur_fdt);
+                rcu_assign_pointer(files->fdt, new_fdt);
+                free_fdtable(cur_fdt);
         } else {
-                /* Somebody expanded while we dropped file_lock */
+                /* Somebody else expanded, so undo our attempt */
                 spin_unlock(&files->file_lock);
-                __free_fdtable(nfdt);
+                __free_fdtable(new_fdt);
                 spin_lock(&files->file_lock);
-                goto out;
         }
-        rcu_assign_pointer(files->fdt, nfdt);
-        free_fdtable(fdt);
-out:
-        return error;
+        return 1;
 }
 
 /*
  * Expand files.
- * Return <0 on error; 0 nothing done; 1 files expanded, we may have blocked.
- * Should be called with the files->file_lock spinlock held for write.
+ * This function will expand the file structures, if the requested size exceeds
+ * the current capacity and there is room for expansion.
+ * Return <0 error code on error; 0 when nothing done; 1 when files were
+ * expanded and execution may have blocked.
+ * The files->file_lock should be held on entry, and will be held on exit.
  */
 int expand_files(struct files_struct *files, int nr)
 {
-        int err, expand = 0;
         struct fdtable *fdt;
 
         fdt = files_fdtable(files);
-        if (nr >= fdt->max_fdset || nr >= fdt->max_fds) {
-                if (fdt->max_fdset >= NR_OPEN ||
-                        fdt->max_fds >= NR_OPEN || nr >= NR_OPEN) {
-                        err = -EMFILE;
-                        goto out;
-                }
-                expand = 1;
-                if ((err = expand_fdtable(files, nr)))
-                        goto out;
-        }
-        err = expand;
-out:
-        return err;
+        /* Do we need to expand? */
+        if (nr < fdt->max_fdset && nr < fdt->max_fds)
+                return 0;
+        /* Can we expand? */
+        if (fdt->max_fdset >= NR_OPEN || fdt->max_fds >= NR_OPEN ||
+            nr >= NR_OPEN)
+                return -EMFILE;
+
+        /* All good, so we try */
+        return expand_fdtable(files, nr);
 }
 
 static void __devinit fdtable_defer_list_init(int cpu)