[PATCH] exportfs: reduce stack usage

[PATCH] exportfs: reduce stack usage

[Randy.Dunlap]

find_exported_dentry() declares
	char nbuf[NAME_MAX+1];
in 2 separate places, and gcc allocates space on the stack for both
of them.  Having just one of them will suffice, if we can put put
with its scope.

Reduces function stack usage on x86-32 from 0x230 to 0x130.

Signed-off-by: Randy Dunlap <rddunlap@osdl.org>


diffstat:=
 fs/exportfs/expfs.c |    4 +---
 1 files changed, 1 insertion(+), 3 deletions(-)

diff -Naurp ./fs/exportfs/expfs.c~expfs_stack ./fs/exportfs/expfs.c
--- ./fs/exportfs/expfs.c~expfs_stack	2004-09-15 19:27:42.000000000 -0700
+++ ./fs/exportfs/expfs.c	2004-09-28 21:35:42.339816784 -0700
@@ -55,7 +55,7 @@ find_exported_dentry(struct super_block 
 	struct list_head *le, *head;
 	struct dentry *toput = NULL;
 	int noprogress;
-
+	char nbuf[NAME_MAX+1];
 
 	/*
 	 * Attempt to find the inode.
@@ -176,7 +176,6 @@ find_exported_dentry(struct super_block 
 			 */
 			struct dentry *ppd;
 			struct dentry *npd;
-			char nbuf[NAME_MAX+1];
 
 			down(&pd->d_inode->i_sem);
 			ppd = CALL(nops,get_parent)(pd);
@@ -241,7 +240,6 @@ find_exported_dentry(struct super_block 
 	/* if we weren't after a directory, have one more step to go */
 	if (result != target_dir) {
 		struct dentry *nresult;
-		char nbuf[NAME_MAX+1];
 		err = CALL(nops,get_name)(target_dir, nbuf, result);
 		if (!err) {
 			down(&target_dir->d_inode->i_sem);


--

Re: [PATCH] exportfs: reduce stack usage

[Neil Brown]

On Tuesday September 28, rddunlap@osdl.org wrote:
> 
> find_exported_dentry() declares
> 	char nbuf[NAME_MAX+1];
> in 2 separate places, and gcc allocates space on the stack for both
> of them.  Having just one of them will suffice, if we can put put
> with its scope.
> 
> Reduces function stack usage on x86-32 from 0x230 to 0x130.

So it does.  I thought gcc was cleverer than that.
I'll add it to my collection.

Thanks,
NeilBrown