linux/fs/nfs/read.c
Christoph Lameter eebd2aa355 Pagecache zeroing: zero_user_segment, zero_user_segments and zero_user
Simplify page cache zeroing of segments of pages through 3 functions

zero_user_segments(page, start1, end1, start2, end2)

        Zeros two segments of the page. It takes the position where to
        start and end the zeroing which avoids length calculations and
	makes code clearer.

zero_user_segment(page, start, end)

        Same for a single segment.

zero_user(page, start, length)

        Length variant for the case where we know the length.

We remove the zero_user_page macro. Issues:

1. Its a macro. Inline functions are preferable.

2. The KM_USER0 macro is only defined for HIGHMEM.

   Having to treat this special case everywhere makes the
   code needlessly complex. The parameter for zeroing is always
   KM_USER0 except in one single case that we open code.

Avoiding KM_USER0 makes a lot of code not having to be dealing
with the special casing for HIGHMEM anymore. Dealing with
kmap is only necessary for HIGHMEM configurations. In those
configurations we use KM_USER0 like we do for a series of other
functions defined in highmem.h.

Since KM_USER0 is depends on HIGHMEM the existing zero_user_page
function could not be a macro. zero_user_* functions introduced
here can be be inline because that constant is not used when these
functions are called.

Also extract the flushing of the caches to be outside of the kmap.

[akpm@linux-foundation.org: fix nfs and ntfs build]
[akpm@linux-foundation.org: fix ntfs build some more]
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Cc: Steven French <sfrench@us.ibm.com>
Cc: Michael Halcrow <mhalcrow@us.ibm.com>
Cc: <linux-ext4@vger.kernel.org>
Cc: Steven Whitehouse <swhiteho@redhat.com>
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
Cc: "J. Bruce Fields" <bfields@fieldses.org>
Cc: Anton Altaparmakov <aia21@cantab.net>
Cc: Mark Fasheh <mark.fasheh@oracle.com>
Cc: David Chinner <dgc@sgi.com>
Cc: Michael Halcrow <mhalcrow@us.ibm.com>
Cc: Steven French <sfrench@us.ibm.com>
Cc: Steven Whitehouse <swhiteho@redhat.com>
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:13 -08:00

611 lines
15 KiB
C

/*
* linux/fs/nfs/read.c
*
* Block I/O for NFS
*
* Partial copy of Linus' read cache modifications to fs/nfs/file.c
* modified for async RPC by okir@monad.swb.de
*/
#include <linux/time.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/fcntl.h>
#include <linux/stat.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/pagemap.h>
#include <linux/sunrpc/clnt.h>
#include <linux/nfs_fs.h>
#include <linux/nfs_page.h>
#include <linux/smp_lock.h>
#include <asm/system.h>
#include "internal.h"
#include "iostat.h"
#define NFSDBG_FACILITY NFSDBG_PAGECACHE
static int nfs_pagein_multi(struct inode *, struct list_head *, unsigned int, size_t, int);
static int nfs_pagein_one(struct inode *, struct list_head *, unsigned int, size_t, int);
static const struct rpc_call_ops nfs_read_partial_ops;
static const struct rpc_call_ops nfs_read_full_ops;
static struct kmem_cache *nfs_rdata_cachep;
static mempool_t *nfs_rdata_mempool;
#define MIN_POOL_READ (32)
struct nfs_read_data *nfs_readdata_alloc(unsigned int pagecount)
{
struct nfs_read_data *p = mempool_alloc(nfs_rdata_mempool, GFP_NOFS);
if (p) {
memset(p, 0, sizeof(*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_NOFS);
if (!p->pagevec) {
mempool_free(p, nfs_rdata_mempool);
p = NULL;
}
}
}
return p;
}
static void nfs_readdata_rcu_free(struct rcu_head *head)
{
struct nfs_read_data *p = container_of(head, struct nfs_read_data, task.u.tk_rcu);
if (p && (p->pagevec != &p->page_array[0]))
kfree(p->pagevec);
mempool_free(p, nfs_rdata_mempool);
}
static void nfs_readdata_free(struct nfs_read_data *rdata)
{
call_rcu_bh(&rdata->task.u.tk_rcu, nfs_readdata_rcu_free);
}
void nfs_readdata_release(void *data)
{
nfs_readdata_free(data);
}
static
int nfs_return_empty_page(struct page *page)
{
zero_user(page, 0, PAGE_CACHE_SIZE);
SetPageUptodate(page);
unlock_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;
}
}
static int nfs_readpage_async(struct nfs_open_context *ctx, struct inode *inode,
struct page *page)
{
LIST_HEAD(one_request);
struct nfs_page *new;
unsigned int len;
len = nfs_page_length(page);
if (len == 0)
return nfs_return_empty_page(page);
new = nfs_create_request(ctx, inode, page, 0, len);
if (IS_ERR(new)) {
unlock_page(page);
return PTR_ERR(new);
}
if (len < PAGE_CACHE_SIZE)
zero_user_segment(page, len, PAGE_CACHE_SIZE);
nfs_list_add_request(new, &one_request);
if (NFS_SERVER(inode)->rsize < PAGE_CACHE_SIZE)
nfs_pagein_multi(inode, &one_request, 1, len, 0);
else
nfs_pagein_one(inode, &one_request, 1, len, 0);
return 0;
}
static void nfs_readpage_release(struct nfs_page *req)
{
unlock_page(req->wb_page);
dprintk("NFS: read done (%s/%Ld %d@%Ld)\n",
req->wb_context->path.dentry->d_inode->i_sb->s_id,
(long long)NFS_FILEID(req->wb_context->path.dentry->d_inode),
req->wb_bytes,
(long long)req_offset(req));
nfs_clear_request(req);
nfs_release_request(req);
}
/*
* Set up the NFS read request struct
*/
static void nfs_read_rpcsetup(struct nfs_page *req, struct nfs_read_data *data,
const struct rpc_call_ops *call_ops,
unsigned int count, unsigned int offset)
{
struct inode *inode = req->wb_context->path.dentry->d_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 = req->wb_context->cred,
};
struct rpc_task_setup task_setup_data = {
.task = &data->task,
.rpc_client = NFS_CLIENT(inode),
.rpc_message = &msg,
.callback_ops = call_ops,
.callback_data = data,
.flags = RPC_TASK_ASYNC | swap_flags,
};
data->req = req;
data->inode = inode;
data->cred = msg.rpc_cred;
data->args.fh = NFS_FH(inode);
data->args.offset = req_offset(req) + offset;
data->args.pgbase = req->wb_pgbase + offset;
data->args.pages = data->pagevec;
data->args.count = count;
data->args.context = req->wb_context;
data->res.fattr = &data->fattr;
data->res.count = count;
data->res.eof = 0;
nfs_fattr_init(&data->fattr);
/* Set up the initial task struct. */
NFS_PROTO(inode)->read_setup(data, &msg);
dprintk("NFS: %5u initiated read call (req %s/%Ld, %u bytes @ offset %Lu)\n",
data->task.tk_pid,
inode->i_sb->s_id,
(long long)NFS_FILEID(inode),
count,
(unsigned long long)data->args.offset);
task = rpc_run_task(&task_setup_data);
if (!IS_ERR(task))
rpc_put_task(task);
}
static void
nfs_async_read_error(struct list_head *head)
{
struct nfs_page *req;
while (!list_empty(head)) {
req = nfs_list_entry(head->next);
nfs_list_remove_request(req);
SetPageError(req->wb_page);
nfs_readpage_release(req);
}
}
/*
* Generate multiple requests to fill a single page.
*
* We optimize to reduce the number of read operations on the wire. If we
* detect that we're reading a page, or an area of a page, that is past the
* end of file, we do not generate NFS read operations but just clear the
* parts of the page that would have come back zero from the server anyway.
*
* We rely on the cached value of i_size to make this determination; another
* client can fill pages on the server past our cached end-of-file, but we
* 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 inode *inode, struct list_head *head, unsigned int npages, size_t count, int flags)
{
struct nfs_page *req = nfs_list_entry(head->next);
struct page *page = req->wb_page;
struct nfs_read_data *data;
size_t rsize = NFS_SERVER(inode)->rsize, nbytes;
unsigned int offset;
int requests = 0;
LIST_HEAD(list);
nfs_list_remove_request(req);
nbytes = count;
do {
size_t len = min(nbytes,rsize);
data = nfs_readdata_alloc(1);
if (!data)
goto out_bad;
INIT_LIST_HEAD(&data->pages);
list_add(&data->pages, &list);
requests++;
nbytes -= len;
} while(nbytes != 0);
atomic_set(&req->wb_complete, requests);
ClearPageError(page);
offset = 0;
nbytes = count;
do {
data = list_entry(list.next, struct nfs_read_data, pages);
list_del_init(&data->pages);
data->pagevec[0] = page;
if (nbytes < rsize)
rsize = nbytes;
nfs_read_rpcsetup(req, data, &nfs_read_partial_ops,
rsize, offset);
offset += rsize;
nbytes -= rsize;
} while (nbytes != 0);
return 0;
out_bad:
while (!list_empty(&list)) {
data = list_entry(list.next, struct nfs_read_data, pages);
list_del(&data->pages);
nfs_readdata_free(data);
}
SetPageError(page);
nfs_readpage_release(req);
return -ENOMEM;
}
static int nfs_pagein_one(struct inode *inode, struct list_head *head, unsigned int npages, size_t count, int flags)
{
struct nfs_page *req;
struct page **pages;
struct nfs_read_data *data;
data = nfs_readdata_alloc(npages);
if (!data)
goto out_bad;
INIT_LIST_HEAD(&data->pages);
pages = data->pagevec;
while (!list_empty(head)) {
req = nfs_list_entry(head->next);
nfs_list_remove_request(req);
nfs_list_add_request(req, &data->pages);
ClearPageError(req->wb_page);
*pages++ = req->wb_page;
}
req = nfs_list_entry(data->pages.next);
nfs_read_rpcsetup(req, data, &nfs_read_full_ops, count, 0);
return 0;
out_bad:
nfs_async_read_error(head);
return -ENOMEM;
}
/*
* This is the callback from RPC telling us whether a reply was
* received or some error occurred (timeout or socket shutdown).
*/
int nfs_readpage_result(struct rpc_task *task, struct nfs_read_data *data)
{
int status;
dprintk("NFS: %s: %5u, (status %d)\n", __FUNCTION__, task->tk_pid,
task->tk_status);
status = NFS_PROTO(data->inode)->read_done(task, data);
if (status != 0)
return status;
nfs_add_stats(data->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);
}
return 0;
}
static int 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 0;
/* This is a short read! */
nfs_inc_stats(data->inode, NFSIOS_SHORTREAD);
/* Has the server at least made some progress? */
if (resp->count == 0)
return 0;
/* Yes, so retry the read at the end of the data */
argp->offset += resp->count;
argp->pgbase += resp->count;
argp->count -= resp->count;
rpc_restart_call(task);
return -EAGAIN;
}
/*
* Handle a read reply that fills part of a page.
*/
static void nfs_readpage_result_partial(struct rpc_task *task, void *calldata)
{
struct nfs_read_data *data = calldata;
struct nfs_page *req = data->req;
struct page *page = req->wb_page;
if (nfs_readpage_result(task, data) != 0)
return;
if (likely(task->tk_status >= 0)) {
nfs_readpage_truncate_uninitialised_page(data);
if (nfs_readpage_retry(task, data) != 0)
return;
}
if (unlikely(task->tk_status < 0))
SetPageError(page);
if (atomic_dec_and_test(&req->wb_complete)) {
if (!PageError(page))
SetPageUptodate(page);
nfs_readpage_release(req);
}
}
static const struct rpc_call_ops nfs_read_partial_ops = {
.rpc_call_done = nfs_readpage_result_partial,
.rpc_release = nfs_readdata_release,
};
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;
/*
* 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.
*/
if (likely(task->tk_status >= 0)) {
nfs_readpage_truncate_uninitialised_page(data);
nfs_readpage_set_pages_uptodate(data);
if (nfs_readpage_retry(task, data) != 0)
return;
}
while (!list_empty(&data->pages)) {
struct nfs_page *req = nfs_list_entry(data->pages.next);
nfs_list_remove_request(req);
nfs_readpage_release(req);
}
}
static const struct rpc_call_ops nfs_read_full_ops = {
.rpc_call_done = nfs_readpage_result_full,
.rpc_release = nfs_readdata_release,
};
/*
* Read a page over NFS.
* We read the page synchronously in the following case:
* - The error flag is set for this page. This happens only when a
* previous async read operation failed.
*/
int nfs_readpage(struct file *file, struct page *page)
{
struct nfs_open_context *ctx;
struct inode *inode = page->mapping->host;
int error;
dprintk("NFS: nfs_readpage (%p %ld@%lu)\n",
page, PAGE_CACHE_SIZE, page->index);
nfs_inc_stats(inode, NFSIOS_VFSREADPAGE);
nfs_add_stats(inode, NFSIOS_READPAGES, 1);
/*
* Try to flush any pending writes to the file..
*
* NOTE! Because we own the page lock, there cannot
* be any new pending writes generated at this point
* for this page (other pages can be written to).
*/
error = nfs_wb_page(inode, page);
if (error)
goto out_unlock;
if (PageUptodate(page))
goto out_unlock;
error = -ESTALE;
if (NFS_STALE(inode))
goto out_unlock;
if (file == NULL) {
error = -EBADF;
ctx = nfs_find_open_context(inode, NULL, FMODE_READ);
if (ctx == NULL)
goto out_unlock;
} else
ctx = get_nfs_open_context(nfs_file_open_context(file));
error = nfs_readpage_async(ctx, inode, page);
put_nfs_open_context(ctx);
return error;
out_unlock:
unlock_page(page);
return error;
}
struct nfs_readdesc {
struct nfs_pageio_descriptor *pgio;
struct nfs_open_context *ctx;
};
static int
readpage_async_filler(void *data, struct page *page)
{
struct nfs_readdesc *desc = (struct nfs_readdesc *)data;
struct inode *inode = page->mapping->host;
struct nfs_page *new;
unsigned int len;
int error;
error = nfs_wb_page(inode, page);
if (error)
goto out_unlock;
if (PageUptodate(page))
goto out_unlock;
len = nfs_page_length(page);
if (len == 0)
return nfs_return_empty_page(page);
new = nfs_create_request(desc->ctx, inode, page, 0, len);
if (IS_ERR(new))
goto out_error;
if (len < PAGE_CACHE_SIZE)
zero_user_segment(page, len, PAGE_CACHE_SIZE);
nfs_pageio_add_request(desc->pgio, new);
return 0;
out_error:
error = PTR_ERR(new);
SetPageError(page);
out_unlock:
unlock_page(page);
return error;
}
int nfs_readpages(struct file *filp, struct address_space *mapping,
struct list_head *pages, unsigned nr_pages)
{
struct nfs_pageio_descriptor pgio;
struct nfs_readdesc desc = {
.pgio = &pgio,
};
struct inode *inode = mapping->host;
struct nfs_server *server = NFS_SERVER(inode);
size_t rsize = server->rsize;
unsigned long npages;
int ret = -ESTALE;
dprintk("NFS: nfs_readpages (%s/%Ld %d)\n",
inode->i_sb->s_id,
(long long)NFS_FILEID(inode),
nr_pages);
nfs_inc_stats(inode, NFSIOS_VFSREADPAGES);
if (NFS_STALE(inode))
goto out;
if (filp == NULL) {
desc.ctx = nfs_find_open_context(inode, NULL, FMODE_READ);
if (desc.ctx == NULL)
return -EBADF;
} else
desc.ctx = get_nfs_open_context(nfs_file_open_context(filp));
if (rsize < PAGE_CACHE_SIZE)
nfs_pageio_init(&pgio, inode, nfs_pagein_multi, rsize, 0);
else
nfs_pageio_init(&pgio, inode, nfs_pagein_one, rsize, 0);
ret = read_cache_pages(mapping, pages, readpage_async_filler, &desc);
nfs_pageio_complete(&pgio);
npages = (pgio.pg_bytes_written + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
nfs_add_stats(inode, NFSIOS_READPAGES, npages);
put_nfs_open_context(desc.ctx);
out:
return ret;
}
int __init nfs_init_readpagecache(void)
{
nfs_rdata_cachep = kmem_cache_create("nfs_read_data",
sizeof(struct nfs_read_data),
0, SLAB_HWCACHE_ALIGN,
NULL);
if (nfs_rdata_cachep == NULL)
return -ENOMEM;
nfs_rdata_mempool = mempool_create_slab_pool(MIN_POOL_READ,
nfs_rdata_cachep);
if (nfs_rdata_mempool == NULL)
return -ENOMEM;
return 0;
}
void nfs_destroy_readpagecache(void)
{
mempool_destroy(nfs_rdata_mempool);
kmem_cache_destroy(nfs_rdata_cachep);
}