608 lines
17 KiB
C
608 lines
17 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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*
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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/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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#define NFSDBG_FACILITY NFSDBG_VFS
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#define VERF_SIZE (2 * sizeof(__u32))
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#define MAX_DIRECTIO_SIZE (4096UL << PAGE_SHIFT)
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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 arithmetic overflow */
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if (size > MAX_DIRECTIO_SIZE)
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return -EFBIG;
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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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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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*/
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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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if (do_dirty)
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set_page_dirty_lock(pages[i]);
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page_cache_release(pages[i]);
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}
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kfree(pages);
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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: size of pages array
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*/
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static int
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nfs_direct_read_seg(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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struct page **pages, int nr_pages)
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{
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const unsigned int rsize = NFS_SERVER(inode)->rsize;
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int tot_bytes = 0;
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int curpage = 0;
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struct nfs_read_data rdata = {
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.inode = inode,
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.cred = ctx->cred,
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.args = {
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.fh = NFS_FH(inode),
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.context = ctx,
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},
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.res = {
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.fattr = &rdata.fattr,
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},
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};
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rdata.args.pgbase = user_addr & ~PAGE_MASK;
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rdata.args.offset = file_offset;
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do {
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int result;
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rdata.args.count = count;
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if (rdata.args.count > rsize)
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rdata.args.count = rsize;
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rdata.args.pages = &pages[curpage];
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dprintk("NFS: direct read: c=%u o=%Ld ua=%lu, pb=%u, cp=%u\n",
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rdata.args.count, (long long) rdata.args.offset,
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user_addr + tot_bytes, rdata.args.pgbase, curpage);
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lock_kernel();
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result = NFS_PROTO(inode)->read(&rdata);
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unlock_kernel();
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if (result <= 0) {
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if (tot_bytes > 0)
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break;
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if (result == -EISDIR)
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result = -EINVAL;
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return result;
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}
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tot_bytes += result;
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if (rdata.res.eof)
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break;
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rdata.args.offset += result;
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rdata.args.pgbase += result;
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curpage += rdata.args.pgbase >> PAGE_SHIFT;
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rdata.args.pgbase &= ~PAGE_MASK;
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count -= result;
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} while (count != 0);
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/* XXX: should we zero the rest of the user's buffer if we
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* hit eof? */
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return tot_bytes;
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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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* generic_file_direct_IO has already pushed out any non-direct
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* writes so that this read will see them when we read from the
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* 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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nfs_free_user_pages(pages, page_count, 1);
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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 int
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nfs_direct_write_seg(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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struct page **pages, 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, 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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.inode = inode,
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.cred = ctx->cred,
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.args = {
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.fh = NFS_FH(inode),
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.context = ctx,
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},
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.res = {
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.fattr = &wdata.fattr,
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.verf = &wdata.verf,
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},
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};
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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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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",
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wdata.args.count, (long long) wdata.args.offset,
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user_addr + tot_bytes, wdata.args.pgbase, curpage);
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lock_kernel();
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result = NFS_PROTO(inode)->write(&wdata);
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unlock_kernel();
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if (result <= 0) {
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if (tot_bytes > 0)
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break;
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goto out;
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}
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if (tot_bytes == 0)
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memcpy(&first_verf.verifier, &wdata.verf.verifier,
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VERF_SIZE);
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if (wdata.verf.committed != NFS_FILE_SYNC) {
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need_commit = 1;
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if (memcmp(&first_verf.verifier,
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&wdata.verf.verifier, VERF_SIZE))
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goto sync_retry;
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}
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tot_bytes += result;
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wdata.args.offset += result;
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wdata.args.pgbase += result;
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curpage += wdata.args.pgbase >> PAGE_SHIFT;
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wdata.args.pgbase &= ~PAGE_MASK;
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request -= result;
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} while (request != 0);
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/*
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* Commit data written so far, even in the event of an error
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*/
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if (need_commit) {
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wdata.args.count = tot_bytes;
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wdata.args.offset = file_offset;
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lock_kernel();
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result = NFS_PROTO(inode)->commit(&wdata);
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unlock_kernel();
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if (result < 0 || memcmp(&first_verf.verifier,
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&wdata.verf.verifier,
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VERF_SIZE) != 0)
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goto sync_retry;
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}
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result = tot_bytes;
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out:
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nfs_end_data_update_defer(inode);
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return result;
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sync_retry:
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wdata.args.stable = NFS_FILE_SYNC;
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goto retry;
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}
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/**
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* nfs_direct_write - For each iov segment, map the user's buffer
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* then generate write and commit 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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* Upon return, generic_file_direct_IO invalidates any cached pages
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* that non-direct readers might access, so they will pick up these
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* writes immediately.
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*/
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static int nfs_direct_write(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(WRITE, 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_write_seg(inode, ctx, user_addr, size,
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file_offset, pages, page_count);
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nfs_free_user_pages(pages, page_count, 0);
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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_IO - NFS address space operation for direct I/O
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* rw: direction (read or write)
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* @iocb: target I/O control block
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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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*/
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ssize_t
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nfs_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov,
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loff_t file_offset, unsigned long nr_segs)
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{
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ssize_t result = -EINVAL;
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struct file *file = iocb->ki_filp;
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struct nfs_open_context *ctx;
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struct dentry *dentry = file->f_dentry;
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struct inode *inode = dentry->d_inode;
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/*
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* No support for async yet
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*/
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if (!is_sync_kiocb(iocb))
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return result;
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ctx = (struct nfs_open_context *)file->private_data;
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switch (rw) {
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case READ:
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dprintk("NFS: direct_IO(read) (%s) off/no(%Lu/%lu)\n",
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dentry->d_name.name, file_offset, nr_segs);
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result = nfs_direct_read(inode, ctx, iov,
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file_offset, nr_segs);
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break;
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case WRITE:
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dprintk("NFS: direct_IO(write) (%s) off/no(%Lu/%lu)\n",
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dentry->d_name.name, file_offset, nr_segs);
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result = nfs_direct_write(inode, ctx, iov,
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file_offset, nr_segs);
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break;
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default:
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break;
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}
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return result;
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}
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/**
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* nfs_file_direct_read - file direct read operation for NFS files
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* @iocb: target I/O control block
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* @buf: user's buffer into which to read data
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* count: number of bytes to read
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* pos: byte offset in file where reading starts
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*
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* We use this function for direct reads instead of calling
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* generic_file_aio_read() in order to avoid gfar's check to see if
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* the request starts before the end of the file. For that check
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* to work, we must generate a GETATTR before each direct read, and
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* even then there is a window between the GETATTR and the subsequent
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* READ where the file size could change. So our preference is simply
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* to do all reads the application wants, and the server will take
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* care of managing the end of file boundary.
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*
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* This function also eliminates unnecessarily updating the file's
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* atime locally, as the NFS server sets the file's atime, and this
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* client must read the updated atime from the server back into its
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* cache.
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*/
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ssize_t
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nfs_file_direct_read(struct kiocb *iocb, char __user *buf, size_t count, loff_t pos)
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{
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ssize_t retval = -EINVAL;
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loff_t *ppos = &iocb->ki_pos;
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struct file *file = iocb->ki_filp;
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struct nfs_open_context *ctx =
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(struct nfs_open_context *) file->private_data;
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struct dentry *dentry = file->f_dentry;
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struct address_space *mapping = file->f_mapping;
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struct inode *inode = mapping->host;
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struct iovec iov = {
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.iov_base = buf,
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.iov_len = count,
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};
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dprintk("nfs: direct read(%s/%s, %lu@%lu)\n",
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dentry->d_parent->d_name.name, dentry->d_name.name,
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(unsigned long) count, (unsigned long) pos);
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if (!is_sync_kiocb(iocb))
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goto out;
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if (count < 0)
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goto out;
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retval = -EFAULT;
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if (!access_ok(VERIFY_WRITE, iov.iov_base, iov.iov_len))
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goto out;
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retval = 0;
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if (!count)
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goto out;
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if (mapping->nrpages) {
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retval = filemap_fdatawrite(mapping);
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if (retval == 0)
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retval = filemap_fdatawait(mapping);
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if (retval)
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goto out;
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}
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retval = nfs_direct_read(inode, ctx, &iov, pos, 1);
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if (retval > 0)
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*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 = -EINVAL;
|
|
loff_t *ppos = &iocb->ki_pos;
|
|
unsigned long limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
|
|
struct file *file = iocb->ki_filp;
|
|
struct nfs_open_context *ctx =
|
|
(struct nfs_open_context *) file->private_data;
|
|
struct dentry *dentry = file->f_dentry;
|
|
struct address_space *mapping = file->f_mapping;
|
|
struct inode *inode = mapping->host;
|
|
struct iovec iov = {
|
|
.iov_base = (char __user *)buf,
|
|
.iov_len = count,
|
|
};
|
|
|
|
dfprintk(VFS, "nfs: direct write(%s/%s(%ld), %lu@%lu)\n",
|
|
dentry->d_parent->d_name.name, dentry->d_name.name,
|
|
inode->i_ino, (unsigned long) count, (unsigned long) pos);
|
|
|
|
if (!is_sync_kiocb(iocb))
|
|
goto out;
|
|
if (count < 0)
|
|
goto out;
|
|
if (pos < 0)
|
|
goto out;
|
|
retval = -EFAULT;
|
|
if (!access_ok(VERIFY_READ, iov.iov_base, iov.iov_len))
|
|
goto out;
|
|
if (file->f_error) {
|
|
retval = file->f_error;
|
|
file->f_error = 0;
|
|
goto out;
|
|
}
|
|
retval = -EFBIG;
|
|
if (limit != RLIM_INFINITY) {
|
|
if (pos >= limit) {
|
|
send_sig(SIGXFSZ, current, 0);
|
|
goto out;
|
|
}
|
|
if (count > limit - (unsigned long) pos)
|
|
count = limit - (unsigned long) pos;
|
|
}
|
|
retval = 0;
|
|
if (!count)
|
|
goto out;
|
|
|
|
if (mapping->nrpages) {
|
|
retval = filemap_fdatawrite(mapping);
|
|
if (retval == 0)
|
|
retval = filemap_fdatawait(mapping);
|
|
if (retval)
|
|
goto out;
|
|
}
|
|
|
|
retval = nfs_direct_write(inode, ctx, &iov, pos, 1);
|
|
if (mapping->nrpages)
|
|
invalidate_inode_pages2(mapping);
|
|
if (retval > 0)
|
|
*ppos = pos + retval;
|
|
|
|
out:
|
|
return retval;
|
|
}
|