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

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

[Vadim Lobanov]

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.)

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;
 }
 
 /*
@@ -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)

Re: [PATCH] Clean up expand_fdtable() and expand_files().

[Randy.Dunlap]

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

Re: [PATCH] Clean up expand_fdtable() and expand_files().

[Vadim Lobanov]

On Tuesday 05 September 2006 09:55, Randy.Dunlap wrote:
> 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.

More comments on the function headers. Gotcha. Will resend.

The problem with kernel-doc in this particular instance is that none of the 
other functions in that file have comments in that particular style; they all 
currently use the mostly-unstructured C comments. If anything, it'd be far 
simpler and cleaner to get this particular patch merged first, and then add 
kernel-doc comments to _all_ the functions in this file at once in a later 
patch.

>
> ---
> ~Randy

-- Vadim Lobanov

Re: [PATCH] Clean up expand_fdtable() and expand_files().

[Randy.Dunlap]

On Tue, 5 Sep 2006 11:56:49 -0700 Vadim Lobanov wrote:

> On Tuesday 05 September 2006 09:55, Randy.Dunlap wrote:
> > 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.
> 
> More comments on the function headers. Gotcha. Will resend.
> 
> The problem with kernel-doc in this particular instance is that none of the 
> other functions in that file have comments in that particular style; they all 
> currently use the mostly-unstructured C comments. If anything, it'd be far 
> simpler and cleaner to get this particular patch merged first, and then add 
> kernel-doc comments to _all_ the functions in this file at once in a later 
> patch.

Sure.  The kernel-doc comment was certainly secondary.

---
~Randy