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SubjectRe: [PATCH] Clean up expand_fdtable() and expand_files().
On Mon, 4 Sep 2006 22:08:36 -0700 Vadim Lobanov wrote:

> Hi,
>
> This patch performs 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. The patch was generated against 2.6.18-rc5-mm1, and
> was successfully run live. Please apply.
>
> (I'm trying out KMail for this patch. I tested this mailer beforehand to make
> sure the patch will come out unmangled, but, as with all things software,
> success is far from guaranteed. :) Please yell if the patch is borked.)

It's not (mechanically) b0rked.

> Signed-off-by: Vadim Lobanov <vlobanov@speakeasy.net>
>
> diff -Npru linux-a/fs/file.c linux-b/fs/file.c
> --- linux-a/fs/file.c 2006-09-01 20:34:12.000000000 -0700
> +++ linux-b/fs/file.c 2006-09-04 16:42:33.000000000 -0700
> @@ -296,37 +296,30 @@ static int expand_fdtable(struct files_s
> __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;

This function didn't previously return a value of 1.
If it can do so now, please document it in the function comments
"header". Using kernel-doc would be good too.

> }
>
> /*
> @@ -336,23 +329,19 @@ out:
> */
> 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)


---
~Randy
-
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