linux/fs/nfs/read.c
Trond Myklebust 8cfb901528 NFS: Always provide aligned buffers to the RPC read layers
Instead of messing around with XDR padding in the RDMA layer, we should
just give the RPC layer an aligned buffer. Try to avoid creating extra
RPC calls by aligning to the smaller value of ALIGN(len, rsize) and
PAGE_SIZE.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
2021-08-30 13:21:38 -04:00

469 lines
12 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/*
* 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/module.h>
#include "nfs4_fs.h"
#include "internal.h"
#include "iostat.h"
#include "fscache.h"
#include "pnfs.h"
#include "nfstrace.h"
#define NFSDBG_FACILITY NFSDBG_PAGECACHE
static const struct nfs_pgio_completion_ops nfs_async_read_completion_ops;
static const struct nfs_rw_ops nfs_rw_read_ops;
static struct kmem_cache *nfs_rdata_cachep;
static struct nfs_pgio_header *nfs_readhdr_alloc(void)
{
struct nfs_pgio_header *p = kmem_cache_zalloc(nfs_rdata_cachep, GFP_KERNEL);
if (p)
p->rw_mode = FMODE_READ;
return p;
}
static void nfs_readhdr_free(struct nfs_pgio_header *rhdr)
{
kmem_cache_free(nfs_rdata_cachep, rhdr);
}
static
int nfs_return_empty_page(struct page *page)
{
zero_user(page, 0, PAGE_SIZE);
SetPageUptodate(page);
unlock_page(page);
return 0;
}
void nfs_pageio_init_read(struct nfs_pageio_descriptor *pgio,
struct inode *inode, bool force_mds,
const struct nfs_pgio_completion_ops *compl_ops)
{
struct nfs_server *server = NFS_SERVER(inode);
const struct nfs_pageio_ops *pg_ops = &nfs_pgio_rw_ops;
#ifdef CONFIG_NFS_V4_1
if (server->pnfs_curr_ld && !force_mds)
pg_ops = server->pnfs_curr_ld->pg_read_ops;
#endif
nfs_pageio_init(pgio, inode, pg_ops, compl_ops, &nfs_rw_read_ops,
server->rsize, 0);
}
EXPORT_SYMBOL_GPL(nfs_pageio_init_read);
static void nfs_pageio_complete_read(struct nfs_pageio_descriptor *pgio)
{
struct nfs_pgio_mirror *pgm;
unsigned long npages;
nfs_pageio_complete(pgio);
/* It doesn't make sense to do mirrored reads! */
WARN_ON_ONCE(pgio->pg_mirror_count != 1);
pgm = &pgio->pg_mirrors[0];
NFS_I(pgio->pg_inode)->read_io += pgm->pg_bytes_written;
npages = (pgm->pg_bytes_written + PAGE_SIZE - 1) >> PAGE_SHIFT;
nfs_add_stats(pgio->pg_inode, NFSIOS_READPAGES, npages);
}
void nfs_pageio_reset_read_mds(struct nfs_pageio_descriptor *pgio)
{
struct nfs_pgio_mirror *mirror;
if (pgio->pg_ops && pgio->pg_ops->pg_cleanup)
pgio->pg_ops->pg_cleanup(pgio);
pgio->pg_ops = &nfs_pgio_rw_ops;
/* read path should never have more than one mirror */
WARN_ON_ONCE(pgio->pg_mirror_count != 1);
mirror = &pgio->pg_mirrors[0];
mirror->pg_bsize = NFS_SERVER(pgio->pg_inode)->rsize;
}
EXPORT_SYMBOL_GPL(nfs_pageio_reset_read_mds);
static void nfs_readpage_release(struct nfs_page *req, int error)
{
struct inode *inode = d_inode(nfs_req_openctx(req)->dentry);
struct page *page = req->wb_page;
dprintk("NFS: read done (%s/%llu %d@%lld)\n", inode->i_sb->s_id,
(unsigned long long)NFS_FILEID(inode), req->wb_bytes,
(long long)req_offset(req));
if (nfs_error_is_fatal_on_server(error) && error != -ETIMEDOUT)
SetPageError(page);
if (nfs_page_group_sync_on_bit(req, PG_UNLOCKPAGE)) {
struct address_space *mapping = page_file_mapping(page);
if (PageUptodate(page))
nfs_readpage_to_fscache(inode, page, 0);
else if (!PageError(page) && !PagePrivate(page))
generic_error_remove_page(mapping, page);
unlock_page(page);
}
nfs_release_request(req);
}
struct nfs_readdesc {
struct nfs_pageio_descriptor pgio;
struct nfs_open_context *ctx;
};
static void nfs_page_group_set_uptodate(struct nfs_page *req)
{
if (nfs_page_group_sync_on_bit(req, PG_UPTODATE))
SetPageUptodate(req->wb_page);
}
static void nfs_read_completion(struct nfs_pgio_header *hdr)
{
unsigned long bytes = 0;
int error;
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;
unsigned long start = req->wb_pgbase;
unsigned long end = req->wb_pgbase + req->wb_bytes;
if (test_bit(NFS_IOHDR_EOF, &hdr->flags)) {
/* note: regions of the page not covered by a
* request are zeroed in readpage_async_filler */
if (bytes > hdr->good_bytes) {
/* nothing in this request was good, so zero
* the full extent of the request */
zero_user_segment(page, start, end);
} else if (hdr->good_bytes - bytes < req->wb_bytes) {
/* part of this request has good bytes, but
* not all. zero the bad bytes */
start += hdr->good_bytes - bytes;
WARN_ON(start < req->wb_pgbase);
zero_user_segment(page, start, end);
}
}
error = 0;
bytes += req->wb_bytes;
if (test_bit(NFS_IOHDR_ERROR, &hdr->flags)) {
if (bytes <= hdr->good_bytes)
nfs_page_group_set_uptodate(req);
else {
error = hdr->error;
xchg(&nfs_req_openctx(req)->error, error);
}
} else
nfs_page_group_set_uptodate(req);
nfs_list_remove_request(req);
nfs_readpage_release(req, error);
}
out:
hdr->release(hdr);
}
static void nfs_initiate_read(struct nfs_pgio_header *hdr,
struct rpc_message *msg,
const struct nfs_rpc_ops *rpc_ops,
struct rpc_task_setup *task_setup_data, int how)
{
struct inode *inode = hdr->inode;
int swap_flags = IS_SWAPFILE(inode) ? NFS_RPC_SWAPFLAGS : 0;
task_setup_data->flags |= swap_flags;
rpc_ops->read_setup(hdr, msg);
trace_nfs_initiate_read(hdr);
}
static void
nfs_async_read_error(struct list_head *head, int error)
{
struct nfs_page *req;
while (!list_empty(head)) {
req = nfs_list_entry(head->next);
nfs_list_remove_request(req);
nfs_readpage_release(req, error);
}
}
static const struct nfs_pgio_completion_ops nfs_async_read_completion_ops = {
.error_cleanup = nfs_async_read_error,
.completion = nfs_read_completion,
};
/*
* This is the callback from RPC telling us whether a reply was
* received or some error occurred (timeout or socket shutdown).
*/
static int nfs_readpage_done(struct rpc_task *task,
struct nfs_pgio_header *hdr,
struct inode *inode)
{
int status = NFS_PROTO(inode)->read_done(task, hdr);
if (status != 0)
return status;
nfs_add_stats(inode, NFSIOS_SERVERREADBYTES, hdr->res.count);
trace_nfs_readpage_done(task, hdr);
if (task->tk_status == -ESTALE) {
nfs_set_inode_stale(inode);
nfs_mark_for_revalidate(inode);
}
return 0;
}
static void nfs_readpage_retry(struct rpc_task *task,
struct nfs_pgio_header *hdr)
{
struct nfs_pgio_args *argp = &hdr->args;
struct nfs_pgio_res *resp = &hdr->res;
/* This is a short read! */
nfs_inc_stats(hdr->inode, NFSIOS_SHORTREAD);
trace_nfs_readpage_short(task, hdr);
/* Has the server at least made some progress? */
if (resp->count == 0) {
nfs_set_pgio_error(hdr, -EIO, argp->offset);
return;
}
/* For non rpc-based layout drivers, retry-through-MDS */
if (!task->tk_ops) {
hdr->pnfs_error = -EAGAIN;
return;
}
/* Yes, so retry the read at the end of the hdr */
hdr->mds_offset += resp->count;
argp->offset += resp->count;
argp->pgbase += resp->count;
argp->count -= resp->count;
resp->count = 0;
resp->eof = 0;
rpc_restart_call_prepare(task);
}
static void nfs_readpage_result(struct rpc_task *task,
struct nfs_pgio_header *hdr)
{
if (hdr->res.eof) {
loff_t pos = hdr->args.offset + hdr->res.count;
unsigned int new = pos - hdr->io_start;
if (hdr->good_bytes > new) {
hdr->good_bytes = new;
set_bit(NFS_IOHDR_EOF, &hdr->flags);
clear_bit(NFS_IOHDR_ERROR, &hdr->flags);
}
} else if (hdr->res.count < hdr->args.count)
nfs_readpage_retry(task, hdr);
}
static int
readpage_async_filler(void *data, struct page *page)
{
struct nfs_readdesc *desc = data;
struct inode *inode = page_file_mapping(page)->host;
unsigned int rsize = NFS_SERVER(inode)->rsize;
struct nfs_page *new;
unsigned int len, aligned_len;
int error;
len = nfs_page_length(page);
if (len == 0)
return nfs_return_empty_page(page);
aligned_len = min_t(unsigned int, ALIGN(len, rsize), PAGE_SIZE);
new = nfs_create_request(desc->ctx, page, 0, aligned_len);
if (IS_ERR(new))
goto out_error;
if (len < PAGE_SIZE)
zero_user_segment(page, len, PAGE_SIZE);
if (!nfs_pageio_add_request(&desc->pgio, new)) {
nfs_list_remove_request(new);
error = desc->pgio.pg_error;
nfs_readpage_release(new, error);
goto out;
}
return 0;
out_error:
error = PTR_ERR(new);
unlock_page(page);
out:
return error;
}
/*
* 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_readdesc desc;
struct inode *inode = page_file_mapping(page)->host;
int ret;
dprintk("NFS: nfs_readpage (%p %ld@%lu)\n",
page, PAGE_SIZE, page_index(page));
nfs_inc_stats(inode, NFSIOS_VFSREADPAGE);
/*
* 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).
*/
ret = nfs_wb_page(inode, page);
if (ret)
goto out_unlock;
if (PageUptodate(page))
goto out_unlock;
ret = -ESTALE;
if (NFS_STALE(inode))
goto out_unlock;
if (file == NULL) {
ret = -EBADF;
desc.ctx = nfs_find_open_context(inode, NULL, FMODE_READ);
if (desc.ctx == NULL)
goto out_unlock;
} else
desc.ctx = get_nfs_open_context(nfs_file_open_context(file));
xchg(&desc.ctx->error, 0);
if (!IS_SYNC(inode)) {
ret = nfs_readpage_from_fscache(desc.ctx, inode, page);
if (ret == 0)
goto out_wait;
}
nfs_pageio_init_read(&desc.pgio, inode, false,
&nfs_async_read_completion_ops);
ret = readpage_async_filler(&desc, page);
if (ret)
goto out;
nfs_pageio_complete_read(&desc.pgio);
ret = desc.pgio.pg_error < 0 ? desc.pgio.pg_error : 0;
out_wait:
if (!ret) {
ret = wait_on_page_locked_killable(page);
if (!PageUptodate(page) && !ret)
ret = xchg(&desc.ctx->error, 0);
}
out:
put_nfs_open_context(desc.ctx);
return ret;
out_unlock:
unlock_page(page);
return ret;
}
int nfs_readpages(struct file *file, struct address_space *mapping,
struct list_head *pages, unsigned nr_pages)
{
struct nfs_readdesc desc;
struct inode *inode = mapping->host;
int ret;
dprintk("NFS: nfs_readpages (%s/%Lu %d)\n",
inode->i_sb->s_id,
(unsigned long long)NFS_FILEID(inode),
nr_pages);
nfs_inc_stats(inode, NFSIOS_VFSREADPAGES);
ret = -ESTALE;
if (NFS_STALE(inode))
goto out;
if (file == NULL) {
ret = -EBADF;
desc.ctx = nfs_find_open_context(inode, NULL, FMODE_READ);
if (desc.ctx == NULL)
goto out;
} else
desc.ctx = get_nfs_open_context(nfs_file_open_context(file));
/* attempt to read as many of the pages as possible from the cache
* - this returns -ENOBUFS immediately if the cookie is negative
*/
ret = nfs_readpages_from_fscache(desc.ctx, inode, mapping,
pages, &nr_pages);
if (ret == 0)
goto read_complete; /* all pages were read */
nfs_pageio_init_read(&desc.pgio, inode, false,
&nfs_async_read_completion_ops);
ret = read_cache_pages(mapping, pages, readpage_async_filler, &desc);
nfs_pageio_complete_read(&desc.pgio);
read_complete:
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_pgio_header),
0, SLAB_HWCACHE_ALIGN,
NULL);
if (nfs_rdata_cachep == NULL)
return -ENOMEM;
return 0;
}
void nfs_destroy_readpagecache(void)
{
kmem_cache_destroy(nfs_rdata_cachep);
}
static const struct nfs_rw_ops nfs_rw_read_ops = {
.rw_alloc_header = nfs_readhdr_alloc,
.rw_free_header = nfs_readhdr_free,
.rw_done = nfs_readpage_done,
.rw_result = nfs_readpage_result,
.rw_initiate = nfs_initiate_read,
};