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-rw-r--r--fs/nfs/read.c437
1 files changed, 211 insertions, 226 deletions
diff --git a/fs/nfs/read.c b/fs/nfs/read.c
index 0a4be28c2ea3..86ced7836214 100644
--- a/fs/nfs/read.c
+++ b/fs/nfs/read.c
@@ -30,43 +30,73 @@
#define NFSDBG_FACILITY NFSDBG_PAGECACHE
static const struct nfs_pageio_ops nfs_pageio_read_ops;
-static const struct rpc_call_ops nfs_read_partial_ops;
-static const struct rpc_call_ops nfs_read_full_ops;
+static const struct rpc_call_ops nfs_read_common_ops;
+static const struct nfs_pgio_completion_ops nfs_async_read_completion_ops;
static struct kmem_cache *nfs_rdata_cachep;
-struct nfs_read_data *nfs_readdata_alloc(unsigned int pagecount)
+struct nfs_read_header *nfs_readhdr_alloc(void)
{
- struct nfs_read_data *p;
-
- p = kmem_cache_zalloc(nfs_rdata_cachep, GFP_KERNEL);
- if (p) {
- INIT_LIST_HEAD(&p->pages);
- p->npages = pagecount;
- if (pagecount <= ARRAY_SIZE(p->page_array))
- p->pagevec = p->page_array;
- else {
- p->pagevec = kcalloc(pagecount, sizeof(struct page *), GFP_KERNEL);
- if (!p->pagevec) {
- kmem_cache_free(nfs_rdata_cachep, p);
- p = NULL;
- }
- }
+ struct nfs_read_header *rhdr;
+
+ rhdr = kmem_cache_zalloc(nfs_rdata_cachep, GFP_KERNEL);
+ if (rhdr) {
+ struct nfs_pgio_header *hdr = &rhdr->header;
+
+ INIT_LIST_HEAD(&hdr->pages);
+ INIT_LIST_HEAD(&hdr->rpc_list);
+ spin_lock_init(&hdr->lock);
+ atomic_set(&hdr->refcnt, 0);
+ }
+ return rhdr;
+}
+
+static struct nfs_read_data *nfs_readdata_alloc(struct nfs_pgio_header *hdr,
+ unsigned int pagecount)
+{
+ struct nfs_read_data *data, *prealloc;
+
+ prealloc = &container_of(hdr, struct nfs_read_header, header)->rpc_data;
+ if (prealloc->header == NULL)
+ data = prealloc;
+ else
+ data = kzalloc(sizeof(*data), GFP_KERNEL);
+ if (!data)
+ goto out;
+
+ if (nfs_pgarray_set(&data->pages, pagecount)) {
+ data->header = hdr;
+ atomic_inc(&hdr->refcnt);
+ } else {
+ if (data != prealloc)
+ kfree(data);
+ data = NULL;
}
- return p;
+out:
+ return data;
}
-void nfs_readdata_free(struct nfs_read_data *p)
+void nfs_readhdr_free(struct nfs_pgio_header *hdr)
{
- if (p && (p->pagevec != &p->page_array[0]))
- kfree(p->pagevec);
- kmem_cache_free(nfs_rdata_cachep, p);
+ struct nfs_read_header *rhdr = container_of(hdr, struct nfs_read_header, header);
+
+ kmem_cache_free(nfs_rdata_cachep, rhdr);
}
void nfs_readdata_release(struct nfs_read_data *rdata)
{
+ struct nfs_pgio_header *hdr = rdata->header;
+ struct nfs_read_header *read_header = container_of(hdr, struct nfs_read_header, header);
+
put_nfs_open_context(rdata->args.context);
- nfs_readdata_free(rdata);
+ if (rdata->pages.pagevec != rdata->pages.page_array)
+ kfree(rdata->pages.pagevec);
+ if (rdata != &read_header->rpc_data)
+ kfree(rdata);
+ else
+ rdata->header = NULL;
+ if (atomic_dec_and_test(&hdr->refcnt))
+ hdr->completion_ops->completion(hdr);
}
static
@@ -78,39 +108,11 @@ int nfs_return_empty_page(struct page *page)
return 0;
}
-static void nfs_readpage_truncate_uninitialised_page(struct nfs_read_data *data)
-{
- unsigned int remainder = data->args.count - data->res.count;
- unsigned int base = data->args.pgbase + data->res.count;
- unsigned int pglen;
- struct page **pages;
-
- if (data->res.eof == 0 || remainder == 0)
- return;
- /*
- * Note: "remainder" can never be negative, since we check for
- * this in the XDR code.
- */
- pages = &data->args.pages[base >> PAGE_CACHE_SHIFT];
- base &= ~PAGE_CACHE_MASK;
- pglen = PAGE_CACHE_SIZE - base;
- for (;;) {
- if (remainder <= pglen) {
- zero_user(*pages, base, remainder);
- break;
- }
- zero_user(*pages, base, pglen);
- pages++;
- remainder -= pglen;
- pglen = PAGE_CACHE_SIZE;
- base = 0;
- }
-}
-
void nfs_pageio_init_read_mds(struct nfs_pageio_descriptor *pgio,
- struct inode *inode)
+ struct inode *inode,
+ const struct nfs_pgio_completion_ops *compl_ops)
{
- nfs_pageio_init(pgio, inode, &nfs_pageio_read_ops,
+ nfs_pageio_init(pgio, inode, &nfs_pageio_read_ops, compl_ops,
NFS_SERVER(inode)->rsize, 0);
}
@@ -121,11 +123,12 @@ void nfs_pageio_reset_read_mds(struct nfs_pageio_descriptor *pgio)
}
EXPORT_SYMBOL_GPL(nfs_pageio_reset_read_mds);
-static void nfs_pageio_init_read(struct nfs_pageio_descriptor *pgio,
- struct inode *inode)
+void nfs_pageio_init_read(struct nfs_pageio_descriptor *pgio,
+ struct inode *inode,
+ const struct nfs_pgio_completion_ops *compl_ops)
{
- if (!pnfs_pageio_init_read(pgio, inode))
- nfs_pageio_init_read_mds(pgio, inode);
+ if (!pnfs_pageio_init_read(pgio, inode, compl_ops))
+ nfs_pageio_init_read_mds(pgio, inode, compl_ops);
}
int nfs_readpage_async(struct nfs_open_context *ctx, struct inode *inode,
@@ -146,9 +149,10 @@ int nfs_readpage_async(struct nfs_open_context *ctx, struct inode *inode,
if (len < PAGE_CACHE_SIZE)
zero_user_segment(page, len, PAGE_CACHE_SIZE);
- nfs_pageio_init_read(&pgio, inode);
+ nfs_pageio_init_read(&pgio, inode, &nfs_async_read_completion_ops);
nfs_pageio_add_request(&pgio, new);
nfs_pageio_complete(&pgio);
+ NFS_I(inode)->read_io += pgio.pg_bytes_written;
return 0;
}
@@ -169,16 +173,49 @@ static void nfs_readpage_release(struct nfs_page *req)
nfs_release_request(req);
}
-int nfs_initiate_read(struct nfs_read_data *data, struct rpc_clnt *clnt,
- const struct rpc_call_ops *call_ops)
+/* Note io was page aligned */
+static void nfs_read_completion(struct nfs_pgio_header *hdr)
+{
+ unsigned long bytes = 0;
+
+ if (test_bit(NFS_IOHDR_REDO, &hdr->flags))
+ goto out;
+ while (!list_empty(&hdr->pages)) {
+ struct nfs_page *req = nfs_list_entry(hdr->pages.next);
+ struct page *page = req->wb_page;
+
+ if (test_bit(NFS_IOHDR_EOF, &hdr->flags)) {
+ if (bytes > hdr->good_bytes)
+ zero_user(page, 0, PAGE_SIZE);
+ else if (hdr->good_bytes - bytes < PAGE_SIZE)
+ zero_user_segment(page,
+ hdr->good_bytes & ~PAGE_MASK,
+ PAGE_SIZE);
+ }
+ bytes += req->wb_bytes;
+ if (test_bit(NFS_IOHDR_ERROR, &hdr->flags)) {
+ if (bytes <= hdr->good_bytes)
+ SetPageUptodate(page);
+ } else
+ SetPageUptodate(page);
+ nfs_list_remove_request(req);
+ nfs_readpage_release(req);
+ }
+out:
+ hdr->release(hdr);
+}
+
+int nfs_initiate_read(struct rpc_clnt *clnt,
+ struct nfs_read_data *data,
+ const struct rpc_call_ops *call_ops, int flags)
{
- struct inode *inode = data->inode;
+ struct inode *inode = data->header->inode;
int swap_flags = IS_SWAPFILE(inode) ? NFS_RPC_SWAPFLAGS : 0;
struct rpc_task *task;
struct rpc_message msg = {
.rpc_argp = &data->args,
.rpc_resp = &data->res,
- .rpc_cred = data->cred,
+ .rpc_cred = data->header->cred,
};
struct rpc_task_setup task_setup_data = {
.task = &data->task,
@@ -187,7 +224,7 @@ int nfs_initiate_read(struct nfs_read_data *data, struct rpc_clnt *clnt,
.callback_ops = call_ops,
.callback_data = data,
.workqueue = nfsiod_workqueue,
- .flags = RPC_TASK_ASYNC | swap_flags,
+ .flags = RPC_TASK_ASYNC | swap_flags | flags,
};
/* Set up the initial task struct. */
@@ -212,19 +249,15 @@ EXPORT_SYMBOL_GPL(nfs_initiate_read);
/*
* Set up the NFS read request struct
*/
-static void nfs_read_rpcsetup(struct nfs_page *req, struct nfs_read_data *data,
+static void nfs_read_rpcsetup(struct nfs_read_data *data,
unsigned int count, unsigned int offset)
{
- struct inode *inode = req->wb_context->dentry->d_inode;
-
- data->req = req;
- data->inode = inode;
- data->cred = req->wb_context->cred;
+ struct nfs_page *req = data->header->req;
- data->args.fh = NFS_FH(inode);
+ data->args.fh = NFS_FH(data->header->inode);
data->args.offset = req_offset(req) + offset;
data->args.pgbase = req->wb_pgbase + offset;
- data->args.pages = data->pagevec;
+ data->args.pages = data->pages.pagevec;
data->args.count = count;
data->args.context = get_nfs_open_context(req->wb_context);
data->args.lock_context = req->wb_lock_context;
@@ -238,9 +271,9 @@ static void nfs_read_rpcsetup(struct nfs_page *req, struct nfs_read_data *data,
static int nfs_do_read(struct nfs_read_data *data,
const struct rpc_call_ops *call_ops)
{
- struct inode *inode = data->args.context->dentry->d_inode;
+ struct inode *inode = data->header->inode;
- return nfs_initiate_read(data, NFS_CLIENT(inode), call_ops);
+ return nfs_initiate_read(NFS_CLIENT(inode), data, call_ops, 0);
}
static int
@@ -253,7 +286,7 @@ nfs_do_multiple_reads(struct list_head *head,
while (!list_empty(head)) {
int ret2;
- data = list_entry(head->next, struct nfs_read_data, list);
+ data = list_first_entry(head, struct nfs_read_data, list);
list_del_init(&data->list);
ret2 = nfs_do_read(data, call_ops);
@@ -275,6 +308,24 @@ nfs_async_read_error(struct list_head *head)
}
}
+static const struct nfs_pgio_completion_ops nfs_async_read_completion_ops = {
+ .error_cleanup = nfs_async_read_error,
+ .completion = nfs_read_completion,
+};
+
+static void nfs_pagein_error(struct nfs_pageio_descriptor *desc,
+ struct nfs_pgio_header *hdr)
+{
+ set_bit(NFS_IOHDR_REDO, &hdr->flags);
+ while (!list_empty(&hdr->rpc_list)) {
+ struct nfs_read_data *data = list_first_entry(&hdr->rpc_list,
+ struct nfs_read_data, list);
+ list_del(&data->list);
+ nfs_readdata_release(data);
+ }
+ desc->pg_completion_ops->error_cleanup(&desc->pg_list);
+}
+
/*
* Generate multiple requests to fill a single page.
*
@@ -288,93 +339,95 @@ nfs_async_read_error(struct list_head *head)
* won't see the new data until our attribute cache is updated. This is more
* or less conventional NFS client behavior.
*/
-static int nfs_pagein_multi(struct nfs_pageio_descriptor *desc, struct list_head *res)
+static int nfs_pagein_multi(struct nfs_pageio_descriptor *desc,
+ struct nfs_pgio_header *hdr)
{
- struct nfs_page *req = nfs_list_entry(desc->pg_list.next);
+ struct nfs_page *req = hdr->req;
struct page *page = req->wb_page;
struct nfs_read_data *data;
size_t rsize = desc->pg_bsize, nbytes;
unsigned int offset;
- int requests = 0;
- int ret = 0;
-
- nfs_list_remove_request(req);
offset = 0;
nbytes = desc->pg_count;
do {
size_t len = min(nbytes,rsize);
- data = nfs_readdata_alloc(1);
- if (!data)
- goto out_bad;
- data->pagevec[0] = page;
- nfs_read_rpcsetup(req, data, len, offset);
- list_add(&data->list, res);
- requests++;
+ data = nfs_readdata_alloc(hdr, 1);
+ if (!data) {
+ nfs_pagein_error(desc, hdr);
+ return -ENOMEM;
+ }
+ data->pages.pagevec[0] = page;
+ nfs_read_rpcsetup(data, len, offset);
+ list_add(&data->list, &hdr->rpc_list);
nbytes -= len;
offset += len;
- } while(nbytes != 0);
- atomic_set(&req->wb_complete, requests);
- desc->pg_rpc_callops = &nfs_read_partial_ops;
- return ret;
-out_bad:
- while (!list_empty(res)) {
- data = list_entry(res->next, struct nfs_read_data, list);
- list_del(&data->list);
- nfs_readdata_release(data);
- }
- nfs_readpage_release(req);
- return -ENOMEM;
+ } while (nbytes != 0);
+
+ nfs_list_remove_request(req);
+ nfs_list_add_request(req, &hdr->pages);
+ desc->pg_rpc_callops = &nfs_read_common_ops;
+ return 0;
}
-static int nfs_pagein_one(struct nfs_pageio_descriptor *desc, struct list_head *res)
+static int nfs_pagein_one(struct nfs_pageio_descriptor *desc,
+ struct nfs_pgio_header *hdr)
{
struct nfs_page *req;
struct page **pages;
- struct nfs_read_data *data;
+ struct nfs_read_data *data;
struct list_head *head = &desc->pg_list;
- int ret = 0;
- data = nfs_readdata_alloc(nfs_page_array_len(desc->pg_base,
- desc->pg_count));
+ data = nfs_readdata_alloc(hdr, nfs_page_array_len(desc->pg_base,
+ desc->pg_count));
if (!data) {
- nfs_async_read_error(head);
- ret = -ENOMEM;
- goto out;
+ nfs_pagein_error(desc, hdr);
+ return -ENOMEM;
}
- pages = data->pagevec;
+ pages = data->pages.pagevec;
while (!list_empty(head)) {
req = nfs_list_entry(head->next);
nfs_list_remove_request(req);
- nfs_list_add_request(req, &data->pages);
+ nfs_list_add_request(req, &hdr->pages);
*pages++ = req->wb_page;
}
- req = nfs_list_entry(data->pages.next);
- nfs_read_rpcsetup(req, data, desc->pg_count, 0);
- list_add(&data->list, res);
- desc->pg_rpc_callops = &nfs_read_full_ops;
-out:
- return ret;
+ nfs_read_rpcsetup(data, desc->pg_count, 0);
+ list_add(&data->list, &hdr->rpc_list);
+ desc->pg_rpc_callops = &nfs_read_common_ops;
+ return 0;
}
-int nfs_generic_pagein(struct nfs_pageio_descriptor *desc, struct list_head *head)
+int nfs_generic_pagein(struct nfs_pageio_descriptor *desc,
+ struct nfs_pgio_header *hdr)
{
if (desc->pg_bsize < PAGE_CACHE_SIZE)
- return nfs_pagein_multi(desc, head);
- return nfs_pagein_one(desc, head);
+ return nfs_pagein_multi(desc, hdr);
+ return nfs_pagein_one(desc, hdr);
}
static int nfs_generic_pg_readpages(struct nfs_pageio_descriptor *desc)
{
- LIST_HEAD(head);
+ struct nfs_read_header *rhdr;
+ struct nfs_pgio_header *hdr;
int ret;
- ret = nfs_generic_pagein(desc, &head);
+ rhdr = nfs_readhdr_alloc();
+ if (!rhdr) {
+ desc->pg_completion_ops->error_cleanup(&desc->pg_list);
+ return -ENOMEM;
+ }
+ hdr = &rhdr->header;
+ nfs_pgheader_init(desc, hdr, nfs_readhdr_free);
+ atomic_inc(&hdr->refcnt);
+ ret = nfs_generic_pagein(desc, hdr);
if (ret == 0)
- ret = nfs_do_multiple_reads(&head, desc->pg_rpc_callops);
+ ret = nfs_do_multiple_reads(&hdr->rpc_list,
+ desc->pg_rpc_callops);
+ if (atomic_dec_and_test(&hdr->refcnt))
+ hdr->completion_ops->completion(hdr);
return ret;
}
@@ -389,20 +442,21 @@ static const struct nfs_pageio_ops nfs_pageio_read_ops = {
*/
int nfs_readpage_result(struct rpc_task *task, struct nfs_read_data *data)
{
+ struct inode *inode = data->header->inode;
int status;
dprintk("NFS: %s: %5u, (status %d)\n", __func__, task->tk_pid,
task->tk_status);
- status = NFS_PROTO(data->inode)->read_done(task, data);
+ status = NFS_PROTO(inode)->read_done(task, data);
if (status != 0)
return status;
- nfs_add_stats(data->inode, NFSIOS_SERVERREADBYTES, data->res.count);
+ nfs_add_stats(inode, NFSIOS_SERVERREADBYTES, data->res.count);
if (task->tk_status == -ESTALE) {
- set_bit(NFS_INO_STALE, &NFS_I(data->inode)->flags);
- nfs_mark_for_revalidate(data->inode);
+ set_bit(NFS_INO_STALE, &NFS_I(inode)->flags);
+ nfs_mark_for_revalidate(inode);
}
return 0;
}
@@ -412,15 +466,13 @@ static void nfs_readpage_retry(struct rpc_task *task, struct nfs_read_data *data
struct nfs_readargs *argp = &data->args;
struct nfs_readres *resp = &data->res;
- if (resp->eof || resp->count == argp->count)
- return;
-
/* This is a short read! */
- nfs_inc_stats(data->inode, NFSIOS_SHORTREAD);
+ nfs_inc_stats(data->header->inode, NFSIOS_SHORTREAD);
/* Has the server at least made some progress? */
- if (resp->count == 0)
+ if (resp->count == 0) {
+ nfs_set_pgio_error(data->header, -EIO, argp->offset);
return;
-
+ }
/* Yes, so retry the read at the end of the data */
data->mds_offset += resp->count;
argp->offset += resp->count;
@@ -429,114 +481,46 @@ static void nfs_readpage_retry(struct rpc_task *task, struct nfs_read_data *data
rpc_restart_call_prepare(task);
}
-/*
- * Handle a read reply that fills part of a page.
- */
-static void nfs_readpage_result_partial(struct rpc_task *task, void *calldata)
+static void nfs_readpage_result_common(struct rpc_task *task, void *calldata)
{
struct nfs_read_data *data = calldata;
-
+ struct nfs_pgio_header *hdr = data->header;
+
+ /* Note the only returns of nfs_readpage_result are 0 and -EAGAIN */
if (nfs_readpage_result(task, data) != 0)
return;
if (task->tk_status < 0)
- return;
-
- nfs_readpage_truncate_uninitialised_page(data);
- nfs_readpage_retry(task, data);
+ nfs_set_pgio_error(hdr, task->tk_status, data->args.offset);
+ else if (data->res.eof) {
+ loff_t bound;
+
+ bound = data->args.offset + data->res.count;
+ spin_lock(&hdr->lock);
+ if (bound < hdr->io_start + hdr->good_bytes) {
+ set_bit(NFS_IOHDR_EOF, &hdr->flags);
+ clear_bit(NFS_IOHDR_ERROR, &hdr->flags);
+ hdr->good_bytes = bound - hdr->io_start;
+ }
+ spin_unlock(&hdr->lock);
+ } else if (data->res.count != data->args.count)
+ nfs_readpage_retry(task, data);
}
-static void nfs_readpage_release_partial(void *calldata)
+static void nfs_readpage_release_common(void *calldata)
{
- struct nfs_read_data *data = calldata;
- struct nfs_page *req = data->req;
- struct page *page = req->wb_page;
- int status = data->task.tk_status;
-
- if (status < 0)
- set_bit(PG_PARTIAL_READ_FAILED, &req->wb_flags);
-
- if (atomic_dec_and_test(&req->wb_complete)) {
- if (!test_bit(PG_PARTIAL_READ_FAILED, &req->wb_flags))
- SetPageUptodate(page);
- nfs_readpage_release(req);
- }
nfs_readdata_release(calldata);
}
void nfs_read_prepare(struct rpc_task *task, void *calldata)
{
struct nfs_read_data *data = calldata;
- NFS_PROTO(data->inode)->read_rpc_prepare(task, data);
-}
-
-static const struct rpc_call_ops nfs_read_partial_ops = {
- .rpc_call_prepare = nfs_read_prepare,
- .rpc_call_done = nfs_readpage_result_partial,
- .rpc_release = nfs_readpage_release_partial,
-};
-
-static void nfs_readpage_set_pages_uptodate(struct nfs_read_data *data)
-{
- unsigned int count = data->res.count;
- unsigned int base = data->args.pgbase;
- struct page **pages;
-
- if (data->res.eof)
- count = data->args.count;
- if (unlikely(count == 0))
- return;
- pages = &data->args.pages[base >> PAGE_CACHE_SHIFT];
- base &= ~PAGE_CACHE_MASK;
- count += base;
- for (;count >= PAGE_CACHE_SIZE; count -= PAGE_CACHE_SIZE, pages++)
- SetPageUptodate(*pages);
- if (count == 0)
- return;
- /* Was this a short read? */
- if (data->res.eof || data->res.count == data->args.count)
- SetPageUptodate(*pages);
-}
-
-/*
- * This is the callback from RPC telling us whether a reply was
- * received or some error occurred (timeout or socket shutdown).
- */
-static void nfs_readpage_result_full(struct rpc_task *task, void *calldata)
-{
- struct nfs_read_data *data = calldata;
-
- if (nfs_readpage_result(task, data) != 0)
- return;
- if (task->tk_status < 0)
- return;
- /*
- * Note: nfs_readpage_retry may change the values of
- * data->args. In the multi-page case, we therefore need
- * to ensure that we call nfs_readpage_set_pages_uptodate()
- * first.
- */
- nfs_readpage_truncate_uninitialised_page(data);
- nfs_readpage_set_pages_uptodate(data);
- nfs_readpage_retry(task, data);
-}
-
-static void nfs_readpage_release_full(void *calldata)
-{
- struct nfs_read_data *data = calldata;
-
- while (!list_empty(&data->pages)) {
- struct nfs_page *req = nfs_list_entry(data->pages.next);
-
- nfs_list_remove_request(req);
- nfs_readpage_release(req);
- }
- nfs_readdata_release(calldata);
+ NFS_PROTO(data->header->inode)->read_rpc_prepare(task, data);
}
-static const struct rpc_call_ops nfs_read_full_ops = {
+static const struct rpc_call_ops nfs_read_common_ops = {
.rpc_call_prepare = nfs_read_prepare,
- .rpc_call_done = nfs_readpage_result_full,
- .rpc_release = nfs_readpage_release_full,
+ .rpc_call_done = nfs_readpage_result_common,
+ .rpc_release = nfs_readpage_release_common,
};
/*
@@ -668,11 +652,12 @@ int nfs_readpages(struct file *filp, struct address_space *mapping,
if (ret == 0)
goto read_complete; /* all pages were read */
- nfs_pageio_init_read(&pgio, inode);
+ nfs_pageio_init_read(&pgio, inode, &nfs_async_read_completion_ops);
ret = read_cache_pages(mapping, pages, readpage_async_filler, &desc);
nfs_pageio_complete(&pgio);
+ NFS_I(inode)->read_io += pgio.pg_bytes_written;
npages = (pgio.pg_bytes_written + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
nfs_add_stats(inode, NFSIOS_READPAGES, npages);
read_complete:
@@ -684,7 +669,7 @@ out:
int __init nfs_init_readpagecache(void)
{
nfs_rdata_cachep = kmem_cache_create("nfs_read_data",
- sizeof(struct nfs_read_data),
+ sizeof(struct nfs_read_header),
0, SLAB_HWCACHE_ALIGN,
NULL);
if (nfs_rdata_cachep == NULL)