![Trond Myklebust](/assets/img/avatar_default.png)
Based on an original patch by Mike O'Connor and Greg Banks of SGI. Mike states: A normal user can panic an NFS client and cause a local DoS with 'judicious'(?) use of O_DIRECT. Any O_DIRECT write to an NFS file where the user buffer starts with a valid mapped page and contains an unmapped page, will crash in this way. I haven't followed the code, but O_DIRECT reads with similar user buffers will probably also crash albeit in different ways. Details: when nfs_get_user_pages() calls get_user_pages(), it detects and correctly handles get_user_pages() returning an error, which happens if the first page covered by the user buffer's address range is unmapped. However, if the first page is mapped but some subsequent page isn't, get_user_pages() will return a positive number which is less than the number of pages requested (this behaviour is sort of analagous to a short write() call and appears to be intentional). nfs_get_user_pages() doesn't detect this and hands off the array of pages (whose last few elements are random rubbish from the newly allocated array memory) to it's caller, whence they go to nfs_direct_write_seg(), which then totally ignores the nr_pages it's given, and calculates its own idea of how many pages are in the array from the user buffer length. Needless to say, when it comes to transmit those uninitialised page* pointers, we see a crash in the network stack. Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
797 lines
22 KiB
C
797 lines
22 KiB
C
/*
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* linux/fs/nfs/direct.c
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*
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* Copyright (C) 2003 by Chuck Lever <cel@netapp.com>
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*
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* High-performance uncached I/O for the Linux NFS client
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*
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* There are important applications whose performance or correctness
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* depends on uncached access to file data. Database clusters
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* (multiple copies of the same instance running on separate hosts)
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* implement their own cache coherency protocol that subsumes file
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* system cache protocols. Applications that process datasets
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* considerably larger than the client's memory do not always benefit
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* from a local cache. A streaming video server, for instance, has no
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* need to cache the contents of a file.
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*
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* When an application requests uncached I/O, all read and write requests
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* are made directly to the server; data stored or fetched via these
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* requests is not cached in the Linux page cache. The client does not
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* correct unaligned requests from applications. All requested bytes are
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* held on permanent storage before a direct write system call returns to
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* an application.
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*
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* Solaris implements an uncached I/O facility called directio() that
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* is used for backups and sequential I/O to very large files. Solaris
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* also supports uncaching whole NFS partitions with "-o forcedirectio,"
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* an undocumented mount option.
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*
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* Designed by Jeff Kimmel, Chuck Lever, and Trond Myklebust, with
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* help from Andrew Morton.
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*
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* 18 Dec 2001 Initial implementation for 2.4 --cel
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* 08 Jul 2002 Version for 2.4.19, with bug fixes --trondmy
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* 08 Jun 2003 Port to 2.5 APIs --cel
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* 31 Mar 2004 Handle direct I/O without VFS support --cel
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* 15 Sep 2004 Parallel async reads --cel
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*
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*/
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#include <linux/config.h>
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#include <linux/errno.h>
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#include <linux/sched.h>
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#include <linux/kernel.h>
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#include <linux/smp_lock.h>
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#include <linux/file.h>
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#include <linux/pagemap.h>
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#include <linux/kref.h>
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#include <linux/nfs_fs.h>
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#include <linux/nfs_page.h>
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#include <linux/sunrpc/clnt.h>
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#include <asm/system.h>
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#include <asm/uaccess.h>
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#include <asm/atomic.h>
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#define NFSDBG_FACILITY NFSDBG_VFS
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#define MAX_DIRECTIO_SIZE (4096UL << PAGE_SHIFT)
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static void nfs_free_user_pages(struct page **pages, int npages, int do_dirty);
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static kmem_cache_t *nfs_direct_cachep;
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/*
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* This represents a set of asynchronous requests that we're waiting on
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*/
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struct nfs_direct_req {
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struct kref kref; /* release manager */
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struct list_head list; /* nfs_read_data structs */
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wait_queue_head_t wait; /* wait for i/o completion */
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struct page ** pages; /* pages in our buffer */
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unsigned int npages; /* count of pages */
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atomic_t complete, /* i/os we're waiting for */
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count, /* bytes actually processed */
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error; /* any reported error */
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};
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/**
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* nfs_get_user_pages - find and set up pages underlying user's buffer
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* rw: direction (read or write)
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* user_addr: starting address of this segment of user's buffer
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* count: size of this segment
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* @pages: returned array of page struct pointers underlying user's buffer
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*/
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static inline int
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nfs_get_user_pages(int rw, unsigned long user_addr, size_t size,
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struct page ***pages)
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{
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int result = -ENOMEM;
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unsigned long page_count;
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size_t array_size;
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/* set an arbitrary limit to prevent type overflow */
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/* XXX: this can probably be as large as INT_MAX */
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if (size > MAX_DIRECTIO_SIZE) {
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*pages = NULL;
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return -EFBIG;
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}
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page_count = (user_addr + size + PAGE_SIZE - 1) >> PAGE_SHIFT;
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page_count -= user_addr >> PAGE_SHIFT;
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array_size = (page_count * sizeof(struct page *));
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*pages = kmalloc(array_size, GFP_KERNEL);
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if (*pages) {
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down_read(¤t->mm->mmap_sem);
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result = get_user_pages(current, current->mm, user_addr,
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page_count, (rw == READ), 0,
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*pages, NULL);
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up_read(¤t->mm->mmap_sem);
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/*
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* If we got fewer pages than expected from get_user_pages(),
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* the user buffer runs off the end of a mapping; return EFAULT.
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*/
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if (result >= 0 && result < page_count) {
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nfs_free_user_pages(*pages, result, 0);
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*pages = NULL;
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result = -EFAULT;
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}
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}
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return result;
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}
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/**
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* nfs_free_user_pages - tear down page struct array
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* @pages: array of page struct pointers underlying target buffer
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* @npages: number of pages in the array
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* @do_dirty: dirty the pages as we release them
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*/
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static void
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nfs_free_user_pages(struct page **pages, int npages, int do_dirty)
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{
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int i;
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for (i = 0; i < npages; i++) {
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struct page *page = pages[i];
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if (do_dirty && !PageCompound(page))
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set_page_dirty_lock(page);
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page_cache_release(page);
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}
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kfree(pages);
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}
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/**
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* nfs_direct_req_release - release nfs_direct_req structure for direct read
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* @kref: kref object embedded in an nfs_direct_req structure
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*
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*/
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static void nfs_direct_req_release(struct kref *kref)
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{
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struct nfs_direct_req *dreq = container_of(kref, struct nfs_direct_req, kref);
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kmem_cache_free(nfs_direct_cachep, dreq);
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}
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/**
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* nfs_direct_read_alloc - allocate nfs_read_data structures for direct read
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* @count: count of bytes for the read request
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* @rsize: local rsize setting
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*
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* Note we also set the number of requests we have in the dreq when we are
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* done. This prevents races with I/O completion so we will always wait
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* until all requests have been dispatched and completed.
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*/
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static struct nfs_direct_req *nfs_direct_read_alloc(size_t nbytes, unsigned int rsize)
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{
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struct list_head *list;
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struct nfs_direct_req *dreq;
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unsigned int reads = 0;
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unsigned int rpages = (rsize + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
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dreq = kmem_cache_alloc(nfs_direct_cachep, SLAB_KERNEL);
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if (!dreq)
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return NULL;
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kref_init(&dreq->kref);
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init_waitqueue_head(&dreq->wait);
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INIT_LIST_HEAD(&dreq->list);
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atomic_set(&dreq->count, 0);
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atomic_set(&dreq->error, 0);
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list = &dreq->list;
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for(;;) {
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struct nfs_read_data *data = nfs_readdata_alloc(rpages);
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if (unlikely(!data)) {
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while (!list_empty(list)) {
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data = list_entry(list->next,
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struct nfs_read_data, pages);
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list_del(&data->pages);
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nfs_readdata_free(data);
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}
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kref_put(&dreq->kref, nfs_direct_req_release);
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return NULL;
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}
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INIT_LIST_HEAD(&data->pages);
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list_add(&data->pages, list);
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data->req = (struct nfs_page *) dreq;
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reads++;
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if (nbytes <= rsize)
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break;
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nbytes -= rsize;
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}
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kref_get(&dreq->kref);
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atomic_set(&dreq->complete, reads);
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return dreq;
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}
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/**
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* nfs_direct_read_result - handle a read reply for a direct read request
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* @data: address of NFS READ operation control block
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* @status: status of this NFS READ operation
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*
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* We must hold a reference to all the pages in this direct read request
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* until the RPCs complete. This could be long *after* we are woken up in
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* nfs_direct_read_wait (for instance, if someone hits ^C on a slow server).
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*/
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static void nfs_direct_read_result(struct nfs_read_data *data, int status)
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{
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struct nfs_direct_req *dreq = (struct nfs_direct_req *) data->req;
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if (likely(status >= 0))
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atomic_add(data->res.count, &dreq->count);
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else
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atomic_set(&dreq->error, status);
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if (unlikely(atomic_dec_and_test(&dreq->complete))) {
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nfs_free_user_pages(dreq->pages, dreq->npages, 1);
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wake_up(&dreq->wait);
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kref_put(&dreq->kref, nfs_direct_req_release);
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}
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}
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/**
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* nfs_direct_read_schedule - dispatch NFS READ operations for a direct read
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* @dreq: address of nfs_direct_req struct for this request
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* @inode: target inode
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* @ctx: target file open context
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* @user_addr: starting address of this segment of user's buffer
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* @count: size of this segment
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* @file_offset: offset in file to begin the operation
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*
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* For each nfs_read_data struct that was allocated on the list, dispatch
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* an NFS READ operation
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*/
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static void nfs_direct_read_schedule(struct nfs_direct_req *dreq,
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struct inode *inode, struct nfs_open_context *ctx,
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unsigned long user_addr, size_t count, loff_t file_offset)
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{
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struct list_head *list = &dreq->list;
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struct page **pages = dreq->pages;
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unsigned int curpage, pgbase;
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unsigned int rsize = NFS_SERVER(inode)->rsize;
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curpage = 0;
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pgbase = user_addr & ~PAGE_MASK;
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do {
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struct nfs_read_data *data;
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unsigned int bytes;
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bytes = rsize;
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if (count < rsize)
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bytes = count;
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data = list_entry(list->next, struct nfs_read_data, pages);
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list_del_init(&data->pages);
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data->inode = inode;
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data->cred = ctx->cred;
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data->args.fh = NFS_FH(inode);
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data->args.context = ctx;
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data->args.offset = file_offset;
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data->args.pgbase = pgbase;
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data->args.pages = &pages[curpage];
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data->args.count = bytes;
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data->res.fattr = &data->fattr;
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data->res.eof = 0;
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data->res.count = bytes;
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NFS_PROTO(inode)->read_setup(data);
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data->task.tk_cookie = (unsigned long) inode;
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data->complete = nfs_direct_read_result;
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lock_kernel();
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rpc_execute(&data->task);
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unlock_kernel();
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dfprintk(VFS, "NFS: %4d initiated direct read call (req %s/%Ld, %u bytes @ offset %Lu)\n",
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data->task.tk_pid,
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inode->i_sb->s_id,
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(long long)NFS_FILEID(inode),
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bytes,
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(unsigned long long)data->args.offset);
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file_offset += bytes;
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pgbase += bytes;
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curpage += pgbase >> PAGE_SHIFT;
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pgbase &= ~PAGE_MASK;
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count -= bytes;
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} while (count != 0);
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}
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/**
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* nfs_direct_read_wait - wait for I/O completion for direct reads
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* @dreq: request on which we are to wait
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* @intr: whether or not this wait can be interrupted
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*
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* Collects and returns the final error value/byte-count.
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*/
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static ssize_t nfs_direct_read_wait(struct nfs_direct_req *dreq, int intr)
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{
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int result = 0;
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if (intr) {
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result = wait_event_interruptible(dreq->wait,
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(atomic_read(&dreq->complete) == 0));
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} else {
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wait_event(dreq->wait, (atomic_read(&dreq->complete) == 0));
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}
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if (!result)
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result = atomic_read(&dreq->error);
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if (!result)
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result = atomic_read(&dreq->count);
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kref_put(&dreq->kref, nfs_direct_req_release);
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return (ssize_t) result;
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}
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/**
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* nfs_direct_read_seg - Read in one iov segment. Generate separate
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* read RPCs for each "rsize" bytes.
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* @inode: target inode
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* @ctx: target file open context
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* @user_addr: starting address of this segment of user's buffer
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* @count: size of this segment
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* @file_offset: offset in file to begin the operation
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* @pages: array of addresses of page structs defining user's buffer
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* @nr_pages: number of pages in the array
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*
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*/
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static ssize_t nfs_direct_read_seg(struct inode *inode,
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struct nfs_open_context *ctx, unsigned long user_addr,
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size_t count, loff_t file_offset, struct page **pages,
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unsigned int nr_pages)
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{
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ssize_t result;
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sigset_t oldset;
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struct rpc_clnt *clnt = NFS_CLIENT(inode);
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struct nfs_direct_req *dreq;
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dreq = nfs_direct_read_alloc(count, NFS_SERVER(inode)->rsize);
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if (!dreq)
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return -ENOMEM;
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dreq->pages = pages;
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dreq->npages = nr_pages;
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rpc_clnt_sigmask(clnt, &oldset);
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nfs_direct_read_schedule(dreq, inode, ctx, user_addr, count,
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file_offset);
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result = nfs_direct_read_wait(dreq, clnt->cl_intr);
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rpc_clnt_sigunmask(clnt, &oldset);
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return result;
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}
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/**
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* nfs_direct_read - For each iov segment, map the user's buffer
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* then generate read RPCs.
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* @inode: target inode
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* @ctx: target file open context
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* @iov: array of vectors that define I/O buffer
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* file_offset: offset in file to begin the operation
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* nr_segs: size of iovec array
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*
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* We've already pushed out any non-direct writes so that this read
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* will see them when we read from the server.
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*/
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static ssize_t
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nfs_direct_read(struct inode *inode, struct nfs_open_context *ctx,
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const struct iovec *iov, loff_t file_offset,
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unsigned long nr_segs)
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{
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ssize_t tot_bytes = 0;
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unsigned long seg = 0;
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while ((seg < nr_segs) && (tot_bytes >= 0)) {
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ssize_t result;
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int page_count;
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struct page **pages;
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const struct iovec *vec = &iov[seg++];
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unsigned long user_addr = (unsigned long) vec->iov_base;
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size_t size = vec->iov_len;
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page_count = nfs_get_user_pages(READ, user_addr, size, &pages);
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if (page_count < 0) {
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nfs_free_user_pages(pages, 0, 0);
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if (tot_bytes > 0)
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break;
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return page_count;
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}
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result = nfs_direct_read_seg(inode, ctx, user_addr, size,
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file_offset, pages, page_count);
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if (result <= 0) {
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if (tot_bytes > 0)
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break;
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return result;
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}
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tot_bytes += result;
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file_offset += result;
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if (result < size)
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break;
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}
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return tot_bytes;
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}
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/**
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* nfs_direct_write_seg - Write out one iov segment. Generate separate
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* write RPCs for each "wsize" bytes, then commit.
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* @inode: target inode
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* @ctx: target file open context
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* user_addr: starting address of this segment of user's buffer
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* count: size of this segment
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* file_offset: offset in file to begin the operation
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* @pages: array of addresses of page structs defining user's buffer
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* nr_pages: size of pages array
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*/
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static ssize_t nfs_direct_write_seg(struct inode *inode,
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struct nfs_open_context *ctx, unsigned long user_addr,
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size_t count, loff_t file_offset, struct page **pages,
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int nr_pages)
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{
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const unsigned int wsize = NFS_SERVER(inode)->wsize;
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size_t request;
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int curpage, need_commit;
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ssize_t result, tot_bytes;
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struct nfs_writeverf first_verf;
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struct nfs_write_data *wdata;
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wdata = nfs_writedata_alloc(NFS_SERVER(inode)->wpages);
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if (!wdata)
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return -ENOMEM;
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wdata->inode = inode;
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wdata->cred = ctx->cred;
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wdata->args.fh = NFS_FH(inode);
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wdata->args.context = ctx;
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wdata->args.stable = NFS_UNSTABLE;
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if (IS_SYNC(inode) || NFS_PROTO(inode)->version == 2 || count <= wsize)
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wdata->args.stable = NFS_FILE_SYNC;
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wdata->res.fattr = &wdata->fattr;
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wdata->res.verf = &wdata->verf;
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nfs_begin_data_update(inode);
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retry:
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need_commit = 0;
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tot_bytes = 0;
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curpage = 0;
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request = count;
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wdata->args.pgbase = user_addr & ~PAGE_MASK;
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wdata->args.offset = file_offset;
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do {
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wdata->args.count = request;
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if (wdata->args.count > wsize)
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wdata->args.count = wsize;
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wdata->args.pages = &pages[curpage];
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|
|
dprintk("NFS: direct write: c=%u o=%Ld ua=%lu, pb=%u, cp=%u\n",
|
|
wdata->args.count, (long long) wdata->args.offset,
|
|
user_addr + tot_bytes, wdata->args.pgbase, curpage);
|
|
|
|
lock_kernel();
|
|
result = NFS_PROTO(inode)->write(wdata);
|
|
unlock_kernel();
|
|
|
|
if (result <= 0) {
|
|
if (tot_bytes > 0)
|
|
break;
|
|
goto out;
|
|
}
|
|
|
|
if (tot_bytes == 0)
|
|
memcpy(&first_verf.verifier, &wdata->verf.verifier,
|
|
sizeof(first_verf.verifier));
|
|
if (wdata->verf.committed != NFS_FILE_SYNC) {
|
|
need_commit = 1;
|
|
if (memcmp(&first_verf.verifier, &wdata->verf.verifier,
|
|
sizeof(first_verf.verifier)))
|
|
goto sync_retry;
|
|
}
|
|
|
|
tot_bytes += result;
|
|
|
|
/* in case of a short write: stop now, let the app recover */
|
|
if (result < wdata->args.count)
|
|
break;
|
|
|
|
wdata->args.offset += result;
|
|
wdata->args.pgbase += result;
|
|
curpage += wdata->args.pgbase >> PAGE_SHIFT;
|
|
wdata->args.pgbase &= ~PAGE_MASK;
|
|
request -= result;
|
|
} while (request != 0);
|
|
|
|
/*
|
|
* Commit data written so far, even in the event of an error
|
|
*/
|
|
if (need_commit) {
|
|
wdata->args.count = tot_bytes;
|
|
wdata->args.offset = file_offset;
|
|
|
|
lock_kernel();
|
|
result = NFS_PROTO(inode)->commit(wdata);
|
|
unlock_kernel();
|
|
|
|
if (result < 0 || memcmp(&first_verf.verifier,
|
|
&wdata->verf.verifier,
|
|
sizeof(first_verf.verifier)) != 0)
|
|
goto sync_retry;
|
|
}
|
|
result = tot_bytes;
|
|
|
|
out:
|
|
nfs_end_data_update(inode);
|
|
nfs_writedata_free(wdata);
|
|
return result;
|
|
|
|
sync_retry:
|
|
wdata->args.stable = NFS_FILE_SYNC;
|
|
goto retry;
|
|
}
|
|
|
|
/**
|
|
* nfs_direct_write - For each iov segment, map the user's buffer
|
|
* then generate write and commit RPCs.
|
|
* @inode: target inode
|
|
* @ctx: target file open context
|
|
* @iov: array of vectors that define I/O buffer
|
|
* file_offset: offset in file to begin the operation
|
|
* nr_segs: size of iovec array
|
|
*
|
|
* Upon return, generic_file_direct_IO invalidates any cached pages
|
|
* that non-direct readers might access, so they will pick up these
|
|
* writes immediately.
|
|
*/
|
|
static ssize_t nfs_direct_write(struct inode *inode,
|
|
struct nfs_open_context *ctx, const struct iovec *iov,
|
|
loff_t file_offset, unsigned long nr_segs)
|
|
{
|
|
ssize_t tot_bytes = 0;
|
|
unsigned long seg = 0;
|
|
|
|
while ((seg < nr_segs) && (tot_bytes >= 0)) {
|
|
ssize_t result;
|
|
int page_count;
|
|
struct page **pages;
|
|
const struct iovec *vec = &iov[seg++];
|
|
unsigned long user_addr = (unsigned long) vec->iov_base;
|
|
size_t size = vec->iov_len;
|
|
|
|
page_count = nfs_get_user_pages(WRITE, user_addr, size, &pages);
|
|
if (page_count < 0) {
|
|
nfs_free_user_pages(pages, 0, 0);
|
|
if (tot_bytes > 0)
|
|
break;
|
|
return page_count;
|
|
}
|
|
|
|
result = nfs_direct_write_seg(inode, ctx, user_addr, size,
|
|
file_offset, pages, page_count);
|
|
nfs_free_user_pages(pages, page_count, 0);
|
|
|
|
if (result <= 0) {
|
|
if (tot_bytes > 0)
|
|
break;
|
|
return result;
|
|
}
|
|
tot_bytes += result;
|
|
file_offset += result;
|
|
if (result < size)
|
|
break;
|
|
}
|
|
return tot_bytes;
|
|
}
|
|
|
|
/**
|
|
* nfs_direct_IO - NFS address space operation for direct I/O
|
|
* rw: direction (read or write)
|
|
* @iocb: target I/O control block
|
|
* @iov: array of vectors that define I/O buffer
|
|
* file_offset: offset in file to begin the operation
|
|
* nr_segs: size of iovec array
|
|
*
|
|
*/
|
|
ssize_t
|
|
nfs_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov,
|
|
loff_t file_offset, unsigned long nr_segs)
|
|
{
|
|
ssize_t result = -EINVAL;
|
|
struct file *file = iocb->ki_filp;
|
|
struct nfs_open_context *ctx;
|
|
struct dentry *dentry = file->f_dentry;
|
|
struct inode *inode = dentry->d_inode;
|
|
|
|
/*
|
|
* No support for async yet
|
|
*/
|
|
if (!is_sync_kiocb(iocb))
|
|
return result;
|
|
|
|
ctx = (struct nfs_open_context *)file->private_data;
|
|
switch (rw) {
|
|
case READ:
|
|
dprintk("NFS: direct_IO(read) (%s) off/no(%Lu/%lu)\n",
|
|
dentry->d_name.name, file_offset, nr_segs);
|
|
|
|
result = nfs_direct_read(inode, ctx, iov,
|
|
file_offset, nr_segs);
|
|
break;
|
|
case WRITE:
|
|
dprintk("NFS: direct_IO(write) (%s) off/no(%Lu/%lu)\n",
|
|
dentry->d_name.name, file_offset, nr_segs);
|
|
|
|
result = nfs_direct_write(inode, ctx, iov,
|
|
file_offset, nr_segs);
|
|
break;
|
|
default:
|
|
break;
|
|
}
|
|
return result;
|
|
}
|
|
|
|
/**
|
|
* nfs_file_direct_read - file direct read operation for NFS files
|
|
* @iocb: target I/O control block
|
|
* @buf: user's buffer into which to read data
|
|
* count: number of bytes to read
|
|
* pos: byte offset in file where reading starts
|
|
*
|
|
* We use this function for direct reads instead of calling
|
|
* generic_file_aio_read() in order to avoid gfar's check to see if
|
|
* the request starts before the end of the file. For that check
|
|
* to work, we must generate a GETATTR before each direct read, and
|
|
* even then there is a window between the GETATTR and the subsequent
|
|
* READ where the file size could change. So our preference is simply
|
|
* to do all reads the application wants, and the server will take
|
|
* care of managing the end of file boundary.
|
|
*
|
|
* This function also eliminates unnecessarily updating the file's
|
|
* atime locally, as the NFS server sets the file's atime, and this
|
|
* client must read the updated atime from the server back into its
|
|
* cache.
|
|
*/
|
|
ssize_t
|
|
nfs_file_direct_read(struct kiocb *iocb, char __user *buf, size_t count, loff_t pos)
|
|
{
|
|
ssize_t retval = -EINVAL;
|
|
loff_t *ppos = &iocb->ki_pos;
|
|
struct file *file = iocb->ki_filp;
|
|
struct nfs_open_context *ctx =
|
|
(struct nfs_open_context *) file->private_data;
|
|
struct address_space *mapping = file->f_mapping;
|
|
struct inode *inode = mapping->host;
|
|
struct iovec iov = {
|
|
.iov_base = buf,
|
|
.iov_len = count,
|
|
};
|
|
|
|
dprintk("nfs: direct read(%s/%s, %lu@%Ld)\n",
|
|
file->f_dentry->d_parent->d_name.name,
|
|
file->f_dentry->d_name.name,
|
|
(unsigned long) count, (long long) pos);
|
|
|
|
if (!is_sync_kiocb(iocb))
|
|
goto out;
|
|
if (count < 0)
|
|
goto out;
|
|
retval = -EFAULT;
|
|
if (!access_ok(VERIFY_WRITE, iov.iov_base, iov.iov_len))
|
|
goto out;
|
|
retval = 0;
|
|
if (!count)
|
|
goto out;
|
|
|
|
retval = nfs_sync_mapping(mapping);
|
|
if (retval)
|
|
goto out;
|
|
|
|
retval = nfs_direct_read(inode, ctx, &iov, pos, 1);
|
|
if (retval > 0)
|
|
*ppos = pos + retval;
|
|
|
|
out:
|
|
return retval;
|
|
}
|
|
|
|
/**
|
|
* nfs_file_direct_write - file direct write operation for NFS files
|
|
* @iocb: target I/O control block
|
|
* @buf: user's buffer from which to write data
|
|
* count: number of bytes to write
|
|
* pos: byte offset in file where writing starts
|
|
*
|
|
* We use this function for direct writes instead of calling
|
|
* generic_file_aio_write() in order to avoid taking the inode
|
|
* semaphore and updating the i_size. The NFS server will set
|
|
* the new i_size and this client must read the updated size
|
|
* back into its cache. We let the server do generic write
|
|
* parameter checking and report problems.
|
|
*
|
|
* We also avoid an unnecessary invocation of generic_osync_inode(),
|
|
* as it is fairly meaningless to sync the metadata of an NFS file.
|
|
*
|
|
* We eliminate local atime updates, see direct read above.
|
|
*
|
|
* We avoid unnecessary page cache invalidations for normal cached
|
|
* readers of this file.
|
|
*
|
|
* Note that O_APPEND is not supported for NFS direct writes, as there
|
|
* is no atomic O_APPEND write facility in the NFS protocol.
|
|
*/
|
|
ssize_t
|
|
nfs_file_direct_write(struct kiocb *iocb, const char __user *buf, size_t count, loff_t pos)
|
|
{
|
|
ssize_t retval;
|
|
struct file *file = iocb->ki_filp;
|
|
struct nfs_open_context *ctx =
|
|
(struct nfs_open_context *) file->private_data;
|
|
struct address_space *mapping = file->f_mapping;
|
|
struct inode *inode = mapping->host;
|
|
struct iovec iov = {
|
|
.iov_base = (char __user *)buf,
|
|
};
|
|
|
|
dfprintk(VFS, "nfs: direct write(%s/%s, %lu@%Ld)\n",
|
|
file->f_dentry->d_parent->d_name.name,
|
|
file->f_dentry->d_name.name,
|
|
(unsigned long) count, (long long) pos);
|
|
|
|
retval = -EINVAL;
|
|
if (!is_sync_kiocb(iocb))
|
|
goto out;
|
|
|
|
retval = generic_write_checks(file, &pos, &count, 0);
|
|
if (retval)
|
|
goto out;
|
|
|
|
retval = -EINVAL;
|
|
if ((ssize_t) count < 0)
|
|
goto out;
|
|
retval = 0;
|
|
if (!count)
|
|
goto out;
|
|
iov.iov_len = count,
|
|
|
|
retval = -EFAULT;
|
|
if (!access_ok(VERIFY_READ, iov.iov_base, iov.iov_len))
|
|
goto out;
|
|
|
|
retval = nfs_sync_mapping(mapping);
|
|
if (retval)
|
|
goto out;
|
|
|
|
retval = nfs_direct_write(inode, ctx, &iov, pos, 1);
|
|
if (mapping->nrpages)
|
|
invalidate_inode_pages2(mapping);
|
|
if (retval > 0)
|
|
iocb->ki_pos = pos + retval;
|
|
|
|
out:
|
|
return retval;
|
|
}
|
|
|
|
int nfs_init_directcache(void)
|
|
{
|
|
nfs_direct_cachep = kmem_cache_create("nfs_direct_cache",
|
|
sizeof(struct nfs_direct_req),
|
|
0, SLAB_RECLAIM_ACCOUNT,
|
|
NULL, NULL);
|
|
if (nfs_direct_cachep == NULL)
|
|
return -ENOMEM;
|
|
|
|
return 0;
|
|
}
|
|
|
|
void nfs_destroy_directcache(void)
|
|
{
|
|
if (kmem_cache_destroy(nfs_direct_cachep))
|
|
printk(KERN_INFO "nfs_direct_cache: not all structures were freed\n");
|
|
}
|