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Subject[PATCH] reduce NFS stack usage
struct nfs_entry, nfs_readdir_descriptor_t, struct nfs_fh, and struct
nfs_fattr are all not-small and shouldn't be placed on the stack
if we can help it. This was noticed in a "do_IRQ stack overflow"
oops trace, by examining the stack pointer deltas.

This patch does the obvious -- uses kmalloc.

Patch against 2.4.23-preXX, but should apply to 2.6.0-test as well.

Untested, unreviewed... enjoy.



===== fs/nfs/dir.c 1.12 vs edited =====
--- 1.12/fs/nfs/dir.c Tue Oct 15 00:59:27 2002
+++ edited/fs/nfs/dir.c Mon Sep 22 15:08:27 2003
@@ -349,14 +349,25 @@
{
struct dentry *dentry = filp->f_dentry;
struct inode *inode = dentry->d_inode;
- nfs_readdir_descriptor_t my_desc,
- *desc = &my_desc;
- struct nfs_entry my_entry;
+ nfs_readdir_descriptor_t *desc;
+ struct nfs_entry *my_entry;
long res;
+ int rc = -EINVAL;
+ void *mem;
+
+ mem = kmalloc(sizeof(struct nfs_entry) +
+ sizeof(nfs_readdir_descriptor_t), GFP_KERNEL);
+ if (!mem)
+ return -ENOMEM;
+
+ my_entry = mem;
+ desc = mem + sizeof(struct nfs_entry);

res = nfs_revalidate(dentry);
- if (res < 0)
- return res;
+ if (res < 0) {
+ rc = (int) res;
+ goto out;
+ }

/*
* filp->f_pos points to the file offset in the page cache.
@@ -365,11 +376,11 @@
* itself.
*/
memset(desc, 0, sizeof(*desc));
- memset(&my_entry, 0, sizeof(my_entry));
+ memset(my_entry, 0, sizeof(my_entry));

desc->file = filp;
desc->target = filp->f_pos;
- desc->entry = &my_entry;
+ desc->entry = my_entry;
desc->decode = NFS_PROTO(inode)->decode_dirent;

while(!desc->entry->eof) {
@@ -393,11 +404,16 @@
break;
}
}
+
if (desc->error < 0)
- return desc->error;
- if (res < 0)
- return res;
- return 0;
+ rc = desc->error;
+ else if (res < 0)
+ rc = res;
+ /* fall through */
+
+out:
+ kfree(mem);
+ return rc;
}

/*
@@ -476,13 +492,22 @@
struct inode *dir;
struct inode *inode;
int error;
- struct nfs_fh fhandle;
- struct nfs_fattr fattr;
+ struct nfs_fh *fhandle;
+ struct nfs_fattr *fattr;
+ void *mem;
+ int rc = 0;

lock_kernel();
dir = dentry->d_parent->d_inode;
inode = dentry->d_inode;

+ mem = kmalloc(sizeof(struct nfs_fh) + sizeof(struct nfs_fattr),
+ GFP_KERNEL);
+ if (!mem)
+ goto out_bad;
+ fhandle = mem;
+ fattr = mem + sizeof(struct nfs_fh);
+
if (!inode) {
if (nfs_neg_need_reval(dir, dentry))
goto out_bad;
@@ -505,18 +530,19 @@
if (NFS_STALE(inode))
goto out_bad;

- error = NFS_PROTO(dir)->lookup(dir, &dentry->d_name, &fhandle, &fattr);
+ error = NFS_PROTO(dir)->lookup(dir, &dentry->d_name, fhandle, fattr);
if (error)
goto out_bad;
- if (memcmp(NFS_FH(inode), &fhandle, sizeof(struct nfs_fh))!= 0)
+ if (memcmp(NFS_FH(inode), fhandle, sizeof(struct nfs_fh))!= 0)
goto out_bad;
- if ((error = nfs_refresh_inode(inode, &fattr)) != 0)
+ if ((error = nfs_refresh_inode(inode, fattr)) != 0)
goto out_bad;

nfs_renew_times(dentry);
out_valid:
- unlock_kernel();
- return 1;
+ rc = 1;
+ goto out;
+
out_bad:
NFS_CACHEINV(dir);
if (inode && S_ISDIR(inode->i_mode)) {
@@ -528,8 +554,14 @@
shrink_dcache_parent(dentry);
}
d_drop(dentry);
+ rc = 0;
+ /* fall through */
+
+out:
unlock_kernel();
- return 0;
+ if (mem)
+ kfree(mem);
+ return rc;
}

/*
-
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