/*
* linux/fs/nfs/pagelist.c
*
* A set of helper functions for managing NFS read and write requests.
* The main purpose of these routines is to provide support for the
* coalescing of several requests into a single RPC call.
*
* Copyright 2000, 2001 (c) Trond Myklebust <trond.myklebust@fys.uio.no>
*
*/
#include <linux/slab.h>
#include <linux/file.h>
#include <linux/sunrpc/clnt.h>
#include <linux/nfs3.h>
#include <linux/nfs4.h>
#include <linux/nfs_page.h>
#include <linux/nfs_fs.h>
#include <linux/nfs_mount.h>
#include <linux/writeback.h>
#define NFS_PARANOIA 1
static struct kmem_cache *nfs_page_cachep;
static inline struct nfs_page *
nfs_page_alloc(void)
{
struct nfs_page *p;
p = kmem_cache_alloc(nfs_page_cachep, GFP_KERNEL);
if (p) {
memset(p, 0, sizeof(*p));
INIT_LIST_HEAD(&p->wb_list);
}
return p;
}
static inline void
nfs_page_free(struct nfs_page *p)
{
kmem_cache_free(nfs_page_cachep, p);
}
/**
* nfs_create_request - Create an NFS read/write request.
* @file: file descriptor to use
* @inode: inode to which the request is attached
* @page: page to write
* @offset: starting offset within the page for the write
* @count: number of bytes to read/write
*
* The page must be locked by the caller. This makes sure we never
* create two different requests for the same page, and avoids
* a possible deadlock when we reach the hard limit on the number
* of dirty pages.
* User should ensure it is safe to sleep in this function.
*/
struct nfs_page *
nfs_create_request(struct nfs_open_context *ctx, struct inode *inode,
struct page *page,
unsigned int offset, unsigned int count)
{
struct nfs_server *server = NFS_SERVER(inode);
struct nfs_page *req;
/* Deal with hard limits. */
for (;;) {
/* try to allocate the request struct */
req = nfs_page_alloc();
if (req != NULL)
break;
/* Try to free up at least one request in order to stay
* below the hard limit
*/
if (signalled() && (server->flags & NFS_MOUNT_INTR))
return ERR_PTR(-ERESTARTSYS);
yield();
}
/* Initialize the request struct. Initially, we assume a
* long write-back delay. This will be adjusted in
* update_nfs_request below if the region is not locked. */
req->wb_page = page;
atomic_set(&req->wb_complete, 0);
req->wb_index = page->index;
page_cache_get(page);
BUG_ON(PagePrivate(page));
BUG_ON(!PageLocked(page));
BUG_ON(page->mapping->host != inode);
req->wb_offset = offset;
req->wb_pgbase = offset;
req->wb_bytes = count;
atomic_set(&req->wb_count, 1);
req->wb_context = get_nfs_open_context(ctx);
return req;
}
/**
* nfs_unlock_request - Unlock request and wake up sleepers.
* @req:
*/
void nfs_unlock_request(struct nfs_page *req)
{
if (!NFS_WBACK_BUSY(req)) {
printk(KERN_ERR "NFS: Invalid unlock attempted\n");
BUG();
}
smp_mb__before_clear_bit();
clear_bit(PG_BUSY, &req->wb_flags);
smp_mb__after_clear_bit();
wake_up_bit(&req->wb_flags, PG_BUSY);
nfs_release_request(req);
}
/**
* nfs_set_page_writeback_locked - Lock a request for writeback
* @req:
*/
int nfs_set_page_writeback_locked(struct nfs_page *req)
{
struct nfs_inode *nfsi = NFS_I(req->wb_context->dentry->d_inode);
if (!nfs_lock_request(req))
return 0;
radix_tree_tag_set(&nfsi->nfs_page_tree, req->wb_index, NFS_PAGE_TAG_WRITEBACK);
return 1;
}
/**
* nfs_clear_page_writeback - Unlock request and wake up sleepers
*/
void nfs_clear_page_writeback(struct nfs_page *req)
{
struct nfs_inode *nfsi = NFS_I(req->wb_context->dentry->d_inode);
if (req->wb_page != NULL) {
spin_lock(&nfsi->req_lock);
radix_tree_tag_clear(&nfsi->nfs_page_tree, req->wb_index, NFS_PAGE_TAG_WRITEBACK);
spin_unlock(&nfsi->req_lock);
}
nfs_unlock_request(req);
}
/**
* nfs_clear_request - Free up all resources allocated to the request
* @req:
*
* Release page resources associated with a write request after it
* has completed.
*/
void nfs_clear_request(struct nfs_page *req)
{
struct page *page = req->wb_page;
if (page != NULL) {
page_cache_release(page);
req->wb_page = NULL;
}
}
/**
* nfs_release_request - Release the count on an NFS read/write request
* @req: request to release
*
* Note: Should never be called with the spinlock held!
*/
void
nfs_release_request(struct nfs_page *req)
{
if (!atomic_dec_and_test(&req->wb_count))
return;
#ifdef NFS_PARANOIA
BUG_ON (!list_empty(&req->wb_list));
BUG_ON (NFS_WBACK_BUSY(req));
#endif
/* Release struct file or cached credential */
nfs_clear_request(req);
put_nfs_open_context(req->wb_context);
nfs_page_free(req);
}
static int nfs_wait_bit_interruptible(void *word)
{
int ret = 0;
if (signal_pending(current))
ret = -ERESTARTSYS;
else
schedule();
return ret;
}
/**
* nfs_wait_on_request - Wait for a request to complete.
* @req: request to wait upon.
*
* Interruptible by signals only if mounted with intr flag.
* The user is responsible for holding a count on the request.
*/
int
nfs_wait_on_request(struct nfs_page *req)
{
struct rpc_clnt *clnt = NFS_CLIENT(req->wb_context->dentry->d_inode);
sigset_t oldmask;
int ret = 0;
if (!test_bit(PG_BUSY, &req->wb_flags))
goto out;
/*
* Note: the call to rpc_clnt_sigmask() suffices to ensure that we
* are not interrupted if intr flag is not set
*/
rpc_clnt_sigmask(clnt, &oldmask);
ret = out_of_line_wait_on_bit(&req->wb_flags, PG_BUSY,
nfs_wait_bit_interruptible, TASK_INTERRUPTIBLE);
rpc_clnt_sigunmask(clnt, &oldmask);
out:
return ret;
}
/**
* nfs_pageio_init - initialise a page io descriptor
* @desc: pointer to descriptor
* @iosize: io block size
*/
void nfs_pageio_init(struct nfs_pageio_descriptor *desc, unsigned int bsize)
{
INIT_LIST_HEAD(&desc->pg_list);
desc->pg_count = 0;
desc->pg_bsize = bsize;
desc->pg_base = 0;
}
/**
* nfs_can_coalesce_requests - test two requests for compatibility
* @prev: pointer to nfs_page
* @req: pointer to nfs_page
*
* The nfs_page structures 'prev' and 'req' are compared to ensure that the
* page data area they describe is contiguous, and that their RPC
* credentials, NFSv4 open state, and lockowners are the same.
*
* Return 'true' if this is the case, else return 'false'.
*/
static int nfs_can_coalesce_requests(struct nfs_page *prev,
struct nfs_page *req)
{
if (req->wb_context->cred != prev->wb_context->cred)
return 0;
if (req->wb_context->lockowner != prev->wb_context->lockowner)
return 0;
if (req->wb_context->state != prev->wb_context->state)
return 0;
if (req->wb_index != (prev->wb_index + 1))
return 0;
if (req->wb_pgbase != 0)
return 0;
if (prev->wb_pgbase + prev->wb_bytes != PAGE_CACHE_SIZE)
return 0;
return 1;
}
/**
* nfs_pageio_add_request - Attempt to coalesce a request into a page list.
* @desc: destination io descriptor
* @req: request
*
* Returns true if the request 'req' was successfully coalesced into the
* existing list of pages 'desc'.
*/
static int nfs_pageio_add_request(struct nfs_pageio_descriptor *desc,
struct nfs_page *req)
{
size_t newlen = req->wb_bytes;
if (desc->pg_count != 0) {
struct nfs_page *prev;
/*
* FIXME: ideally we should be able to coalesce all requests
* that are not block boundary aligned, but currently this
* is problematic for the case of bsize < PAGE_CACHE_SIZE,
* since nfs_flush_multi and nfs_pagein_multi assume you
* can have only one struct nfs_page.
*/
newlen += desc->pg_count;
if (desc->pg_base + newlen > desc->pg_bsize)
return 0;
prev = nfs_list_entry(desc->pg_list.prev);
if (!nfs_can_coalesce_requests(prev, req))
return 0;
} else
desc->pg_base = req->wb_pgbase;
nfs_list_remove_request(req);
nfs_list_add_request(req, &desc->pg_list);
desc->pg_count = newlen;
return 1;
}
/**
* nfs_pageio_add_list - Split coalesced requests out from a list.
* @desc: destination io descriptor
* @head: source list
*
* Moves a maximum of 'nmax' elements from one list to another.
* The elements are checked to ensure that they form a contiguous set
* of pages, and that the RPC credentials are the same.
*/
void nfs_pageio_add_list(struct nfs_pageio_descriptor *desc,
struct list_head *head)
{
while (!list_empty(head)) {
struct nfs_page *req = nfs_list_entry(head->next);
if (!nfs_pageio_add_request(desc, req))
break;
}
}
#define NFS_SCAN_MAXENTRIES 16
/**
* nfs_scan_dirty - Scan the radix tree for dirty requests
* @mapping: pointer to address space
* @wbc: writeback_control structure
* @dst: Destination list
*
* Moves elements from one of the inode request lists.
* If the number of requests is set to 0, the entire address_space
* starting at index idx_start, is scanned.
* The requests are *not* checked to ensure that they form a contiguous set.
* You must be holding the inode's req_lock when calling this function
*/
long nfs_scan_dirty(struct address_space *mapping,
struct writeback_control *wbc,
struct list_head *dst)
{
struct nfs_inode *nfsi = NFS_I(mapping->host);
struct nfs_page *pgvec[NFS_SCAN_MAXENTRIES];
struct nfs_page *req;
pgoff_t idx_start, idx_end;
long res = 0;
int found, i;
if (nfsi->ndirty == 0)
return 0;
if (wbc->range_cyclic) {
idx_start = 0;
idx_end = ULONG_MAX;
} else if (wbc->range_end == 0) {
idx_start = wbc->range_start >> PAGE_CACHE_SHIFT;
idx_end = ULONG_MAX;
} else {
idx_start = wbc->range_start >> PAGE_CACHE_SHIFT;
idx_end = wbc->range_end >> PAGE_CACHE_SHIFT;
}
for (;;) {
unsigned int toscan = NFS_SCAN_MAXENTRIES;
found = radix_tree_gang_lookup_tag(&nfsi->nfs_page_tree,
(void **)&pgvec[0], idx_start, toscan,
NFS_PAGE_TAG_DIRTY);
/* Did we make progress? */
if (found <= 0)
break;
for (i = 0; i < found; i++) {
req = pgvec[i];
if (!wbc->range_cyclic && req->wb_index > idx_end)
goto out;
/* Try to lock request and mark it for writeback */
if (!nfs_set_page_writeback_locked(req))
goto next;
radix_tree_tag_clear(&nfsi->nfs_page_tree,
req->wb_index, NFS_PAGE_TAG_DIRTY);
nfsi->ndirty--;
nfs_list_remove_request(req);
nfs_list_add_request(req, dst);
res++;
if (res == LONG_MAX)
goto out;
next:
idx_start = req->wb_index + 1;
}
}
out:
WARN_ON ((nfsi->ndirty == 0) != list_empty(&nfsi->dirty));
return res;
}
/**
* nfs_scan_list - Scan a list for matching requests
* @nfsi: NFS inode
* @head: One of the NFS inode request lists
* @dst: Destination list
* @idx_start: lower bound of page->index to scan
* @npages: idx_start + npages sets the upper bound to scan.
*
* Moves elements from one of the inode request lists.
* If the number of requests is set to 0, the entire address_space
* starting at index idx_start, is scanned.
* The requests are *not* checked to ensure that they form a contiguous set.
* You must be holding the inode's req_lock when calling this function
*/
int nfs_scan_list(struct nfs_inode *nfsi, struct list_head *head,
struct list_head *dst, unsigned long idx_start,
unsigned int npages)
{
struct nfs_page *pgvec[NFS_SCAN_MAXENTRIES];
struct nfs_page *req;
unsigned long idx_end;
int found, i;
int res;
res = 0;
if (npages == 0)
idx_end = ~0;
else
idx_end = idx_start + npages - 1;
for (;;) {
found = radix_tree_gang_lookup(&nfsi->nfs_page_tree,
(void **)&pgvec[0], idx_start,
NFS_SCAN_MAXENTRIES);
if (found <= 0)
break;
for (i = 0; i < found; i++) {
req = pgvec[i];
if (req->wb_index > idx_end)
goto out;
idx_start = req->wb_index + 1;
if (req->wb_list_head != head)
continue;
if (nfs_set_page_writeback_locked(req)) {
nfs_list_remove_request(req);
nfs_list_add_request(req, dst);
res++;
}
}
}
out:
return res;
}
int __init nfs_init_nfspagecache(void)
{
nfs_page_cachep = kmem_cache_create("nfs_page",
sizeof(struct nfs_page),
0, SLAB_HWCACHE_ALIGN,
NULL, NULL);
if (nfs_page_cachep == NULL)
return -ENOMEM;
return 0;
}
void nfs_destroy_nfspagecache(void)
{
kmem_cache_destroy(nfs_page_cachep);
}
