[PATCH v4 14/21] NFS: Reduce readdir stack usage

trondmy
2020-11-07T14:13:50Z

The descriptor and the struct nfs_entry are both large structures,
so don't allocate them from the stack.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
---
fs/nfs/dir.c | 58 ++++++++++++++++++++++++++++++----------------------
1 file changed, 33 insertions(+), 25 deletions(-)

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 48856cee10de..c3af54640f6c 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -761,23 +761,24 @@ static
int nfs_readdir_xdr_to_array(nfs_readdir_descriptor_t *desc, struct page *page, struct inode *inode)
{
struct page **pages;
- struct nfs_entry entry;
+ struct nfs_entry *entry;
size_t array_size;
size_t dtsize = NFS_SERVER(inode)->dtsize;
int status = -ENOMEM;

- entry.prev_cookie = 0;
- entry.cookie = nfs_readdir_page_last_cookie(page);
- entry.eof = 0;
- entry.fh = nfs_alloc_fhandle();
- entry.fattr = nfs_alloc_fattr();
- entry.server = NFS_SERVER(inode);
- if (entry.fh == NULL || entry.fattr == NULL)
+ entry = kzalloc(sizeof(*entry), GFP_KERNEL);
+ if (!entry)
+ return -ENOMEM;
+ entry->cookie = nfs_readdir_page_last_cookie(page);
+ entry->fh = nfs_alloc_fhandle();
+ entry->fattr = nfs_alloc_fattr();
+ entry->server = NFS_SERVER(inode);
+ if (entry->fh == NULL || entry->fattr == NULL)
goto out;

- entry.label = nfs4_label_alloc(NFS_SERVER(inode), GFP_NOWAIT);
- if (IS_ERR(entry.label)) {
- status = PTR_ERR(entry.label);
+ entry->label = nfs4_label_alloc(NFS_SERVER(inode), GFP_NOWAIT);
+ if (IS_ERR(entry->label)) {
+ status = PTR_ERR(entry->label);
goto out;
}

@@ -788,7 +789,7 @@ int nfs_readdir_xdr_to_array(nfs_readdir_descriptor_t *desc, struct page *page,

do {
unsigned int pglen;
- status = nfs_readdir_xdr_filler(desc, entry.cookie,
+ status = nfs_readdir_xdr_filler(desc, entry->cookie,
pages, dtsize);
if (status < 0)
break;
@@ -799,15 +800,16 @@ int nfs_readdir_xdr_to_array(nfs_readdir_descriptor_t *desc, struct page *page,
break;
}

- status = nfs_readdir_page_filler(desc, &entry, pages, page, pglen);
+ status = nfs_readdir_page_filler(desc, entry, pages, page, pglen);
} while (!status && nfs_readdir_page_needs_filling(page));

nfs_readdir_free_pages(pages, array_size);
out_release_label:
- nfs4_label_free(entry.label);
+ nfs4_label_free(entry->label);
out:
- nfs_free_fattr(entry.fattr);
- nfs_free_fhandle(entry.fh);
+ nfs_free_fattr(entry->fattr);
+ nfs_free_fhandle(entry->fh);
+ kfree(entry);
return status;
}

@@ -974,13 +976,8 @@ static int nfs_readdir(struct file *file, struct dir_context *ctx)
struct dentry *dentry = file_dentry(file);
struct inode *inode = d_inode(dentry);
struct nfs_open_dir_context *dir_ctx = file->private_data;
- nfs_readdir_descriptor_t my_desc = {
- .file = file,
- .ctx = ctx,
- .plus = nfs_use_readdirplus(inode, ctx),
- },
- *desc = &my_desc;
- int res = 0;
+ struct nfs_readdir_descriptor *desc;
+ int res;

dfprintk(FILE, "NFS: readdir(%pD2) starting at cookie %llu\n",
file, (long long)ctx->pos);
@@ -992,10 +989,19 @@ static int nfs_readdir(struct file *file, struct dir_context *ctx)
* to either find the entry with the appropriate number or
* revalidate the cookie.
*/
- if (ctx->pos == 0 || nfs_attribute_cache_expired(inode))
+ if (ctx->pos == 0 || nfs_attribute_cache_expired(inode)) {
res = nfs_revalidate_mapping(inode, file->f_mapping);
- if (res < 0)
+ if (res < 0)
+ goto out;
+ }
+
+ res = -ENOMEM;
+ desc = kzalloc(sizeof(*desc), GFP_KERNEL);
+ if (!desc)
goto out;
+ desc->file = file;
+ desc->ctx = ctx;
+ desc->plus = nfs_use_readdirplus(inode, ctx);

spin_lock(&file->f_lock);
desc->dir_cookie = dir_ctx->dir_cookie;
@@ -1040,6 +1046,8 @@ static int nfs_readdir(struct file *file, struct dir_context *ctx)
dir_ctx->attr_gencount = desc->attr_gencount;
spin_unlock(&file->f_lock);

+ kfree(desc);
+
out:
dfprintk(FILE, "NFS: readdir(%pD2) returns %d\n", file, res);
return res;
--
2.28.0