linux/fs/nfs/file.c
Trond Myklebust cd52ed3553 NFS: Avoid races between writebacks and truncation
Currently, there is no serialisation between NFS asynchronous writebacks
and truncation at the page level due to the fact that nfs_sync_inode()
cannot lock the pages that it is about to write out.

This means that it is possible to be flushing out data (and calling something
like set_page_writeback()) while the page cache is busy evicting the page.
Oops...

Use the hooks provided in try_to_release_page() to ensure that dirty pages
are always written back to storage before we evict them.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
2006-03-20 13:44:04 -05:00

569 lines
15 KiB
C

/*
* linux/fs/nfs/file.c
*
* Copyright (C) 1992 Rick Sladkey
*
* Changes Copyright (C) 1994 by Florian La Roche
* - Do not copy data too often around in the kernel.
* - In nfs_file_read the return value of kmalloc wasn't checked.
* - Put in a better version of read look-ahead buffering. Original idea
* and implementation by Wai S Kok elekokws@ee.nus.sg.
*
* Expire cache on write to a file by Wai S Kok (Oct 1994).
*
* Total rewrite of read side for new NFS buffer cache.. Linus.
*
* nfs regular file handling functions
*/
#include <linux/time.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/fcntl.h>
#include <linux/stat.h>
#include <linux/nfs_fs.h>
#include <linux/nfs_mount.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/pagemap.h>
#include <linux/smp_lock.h>
#include <asm/uaccess.h>
#include <asm/system.h>
#include "delegation.h"
#define NFSDBG_FACILITY NFSDBG_FILE
static int nfs_file_open(struct inode *, struct file *);
static int nfs_file_release(struct inode *, struct file *);
static loff_t nfs_file_llseek(struct file *file, loff_t offset, int origin);
static int nfs_file_mmap(struct file *, struct vm_area_struct *);
static ssize_t nfs_file_sendfile(struct file *, loff_t *, size_t, read_actor_t, void *);
static ssize_t nfs_file_read(struct kiocb *, char __user *, size_t, loff_t);
static ssize_t nfs_file_write(struct kiocb *, const char __user *, size_t, loff_t);
static int nfs_file_flush(struct file *);
static int nfs_fsync(struct file *, struct dentry *dentry, int datasync);
static int nfs_check_flags(int flags);
static int nfs_lock(struct file *filp, int cmd, struct file_lock *fl);
static int nfs_flock(struct file *filp, int cmd, struct file_lock *fl);
struct file_operations nfs_file_operations = {
.llseek = nfs_file_llseek,
.read = do_sync_read,
.write = do_sync_write,
.aio_read = nfs_file_read,
.aio_write = nfs_file_write,
.mmap = nfs_file_mmap,
.open = nfs_file_open,
.flush = nfs_file_flush,
.release = nfs_file_release,
.fsync = nfs_fsync,
.lock = nfs_lock,
.flock = nfs_flock,
.sendfile = nfs_file_sendfile,
.check_flags = nfs_check_flags,
};
struct inode_operations nfs_file_inode_operations = {
.permission = nfs_permission,
.getattr = nfs_getattr,
.setattr = nfs_setattr,
};
#ifdef CONFIG_NFS_V3
struct inode_operations nfs3_file_inode_operations = {
.permission = nfs_permission,
.getattr = nfs_getattr,
.setattr = nfs_setattr,
.listxattr = nfs3_listxattr,
.getxattr = nfs3_getxattr,
.setxattr = nfs3_setxattr,
.removexattr = nfs3_removexattr,
};
#endif /* CONFIG_NFS_v3 */
/* Hack for future NFS swap support */
#ifndef IS_SWAPFILE
# define IS_SWAPFILE(inode) (0)
#endif
static int nfs_check_flags(int flags)
{
if ((flags & (O_APPEND | O_DIRECT)) == (O_APPEND | O_DIRECT))
return -EINVAL;
return 0;
}
/*
* Open file
*/
static int
nfs_file_open(struct inode *inode, struct file *filp)
{
struct nfs_server *server = NFS_SERVER(inode);
int (*open)(struct inode *, struct file *);
int res;
res = nfs_check_flags(filp->f_flags);
if (res)
return res;
lock_kernel();
/* Do NFSv4 open() call */
if ((open = server->rpc_ops->file_open) != NULL)
res = open(inode, filp);
unlock_kernel();
return res;
}
static int
nfs_file_release(struct inode *inode, struct file *filp)
{
/* Ensure that dirty pages are flushed out with the right creds */
if (filp->f_mode & FMODE_WRITE)
filemap_fdatawrite(filp->f_mapping);
return NFS_PROTO(inode)->file_release(inode, filp);
}
/**
* nfs_revalidate_file - Revalidate the page cache & related metadata
* @inode - pointer to inode struct
* @file - pointer to file
*/
static int nfs_revalidate_file(struct inode *inode, struct file *filp)
{
struct nfs_inode *nfsi = NFS_I(inode);
int retval = 0;
if ((nfsi->cache_validity & (NFS_INO_REVAL_PAGECACHE|NFS_INO_INVALID_ATTR))
|| nfs_attribute_timeout(inode))
retval = __nfs_revalidate_inode(NFS_SERVER(inode), inode);
nfs_revalidate_mapping(inode, filp->f_mapping);
return 0;
}
/**
* nfs_revalidate_size - Revalidate the file size
* @inode - pointer to inode struct
* @file - pointer to struct file
*
* Revalidates the file length. This is basically a wrapper around
* nfs_revalidate_inode() that takes into account the fact that we may
* have cached writes (in which case we don't care about the server's
* idea of what the file length is), or O_DIRECT (in which case we
* shouldn't trust the cache).
*/
static int nfs_revalidate_file_size(struct inode *inode, struct file *filp)
{
struct nfs_server *server = NFS_SERVER(inode);
struct nfs_inode *nfsi = NFS_I(inode);
if (server->flags & NFS_MOUNT_NOAC)
goto force_reval;
if (filp->f_flags & O_DIRECT)
goto force_reval;
if (nfsi->npages != 0)
return 0;
if (!(nfsi->cache_validity & NFS_INO_REVAL_PAGECACHE) && !nfs_attribute_timeout(inode))
return 0;
force_reval:
return __nfs_revalidate_inode(server, inode);
}
static loff_t nfs_file_llseek(struct file *filp, loff_t offset, int origin)
{
/* origin == SEEK_END => we must revalidate the cached file length */
if (origin == 2) {
struct inode *inode = filp->f_mapping->host;
int retval = nfs_revalidate_file_size(inode, filp);
if (retval < 0)
return (loff_t)retval;
}
return remote_llseek(filp, offset, origin);
}
/*
* Flush all dirty pages, and check for write errors.
*
*/
static int
nfs_file_flush(struct file *file)
{
struct nfs_open_context *ctx = (struct nfs_open_context *)file->private_data;
struct inode *inode = file->f_dentry->d_inode;
int status;
dfprintk(VFS, "nfs: flush(%s/%ld)\n", inode->i_sb->s_id, inode->i_ino);
if ((file->f_mode & FMODE_WRITE) == 0)
return 0;
lock_kernel();
/* Ensure that data+attribute caches are up to date after close() */
status = nfs_wb_all(inode);
if (!status) {
status = ctx->error;
ctx->error = 0;
if (!status)
nfs_revalidate_inode(NFS_SERVER(inode), inode);
}
unlock_kernel();
return status;
}
static ssize_t
nfs_file_read(struct kiocb *iocb, char __user * buf, size_t count, loff_t pos)
{
struct dentry * dentry = iocb->ki_filp->f_dentry;
struct inode * inode = dentry->d_inode;
ssize_t result;
#ifdef CONFIG_NFS_DIRECTIO
if (iocb->ki_filp->f_flags & O_DIRECT)
return nfs_file_direct_read(iocb, buf, count, pos);
#endif
dfprintk(VFS, "nfs: read(%s/%s, %lu@%lu)\n",
dentry->d_parent->d_name.name, dentry->d_name.name,
(unsigned long) count, (unsigned long) pos);
result = nfs_revalidate_file(inode, iocb->ki_filp);
if (!result)
result = generic_file_aio_read(iocb, buf, count, pos);
return result;
}
static ssize_t
nfs_file_sendfile(struct file *filp, loff_t *ppos, size_t count,
read_actor_t actor, void *target)
{
struct dentry *dentry = filp->f_dentry;
struct inode *inode = dentry->d_inode;
ssize_t res;
dfprintk(VFS, "nfs: sendfile(%s/%s, %lu@%Lu)\n",
dentry->d_parent->d_name.name, dentry->d_name.name,
(unsigned long) count, (unsigned long long) *ppos);
res = nfs_revalidate_file(inode, filp);
if (!res)
res = generic_file_sendfile(filp, ppos, count, actor, target);
return res;
}
static int
nfs_file_mmap(struct file * file, struct vm_area_struct * vma)
{
struct dentry *dentry = file->f_dentry;
struct inode *inode = dentry->d_inode;
int status;
dfprintk(VFS, "nfs: mmap(%s/%s)\n",
dentry->d_parent->d_name.name, dentry->d_name.name);
status = nfs_revalidate_file(inode, file);
if (!status)
status = generic_file_mmap(file, vma);
return status;
}
/*
* Flush any dirty pages for this process, and check for write errors.
* The return status from this call provides a reliable indication of
* whether any write errors occurred for this process.
*/
static int
nfs_fsync(struct file *file, struct dentry *dentry, int datasync)
{
struct nfs_open_context *ctx = (struct nfs_open_context *)file->private_data;
struct inode *inode = dentry->d_inode;
int status;
dfprintk(VFS, "nfs: fsync(%s/%ld)\n", inode->i_sb->s_id, inode->i_ino);
lock_kernel();
status = nfs_wb_all(inode);
if (!status) {
status = ctx->error;
ctx->error = 0;
}
unlock_kernel();
return status;
}
/*
* This does the "real" work of the write. The generic routine has
* allocated the page, locked it, done all the page alignment stuff
* calculations etc. Now we should just copy the data from user
* space and write it back to the real medium..
*
* If the writer ends up delaying the write, the writer needs to
* increment the page use counts until he is done with the page.
*/
static int nfs_prepare_write(struct file *file, struct page *page, unsigned offset, unsigned to)
{
return nfs_flush_incompatible(file, page);
}
static int nfs_commit_write(struct file *file, struct page *page, unsigned offset, unsigned to)
{
long status;
lock_kernel();
status = nfs_updatepage(file, page, offset, to-offset);
unlock_kernel();
return status;
}
static int nfs_invalidate_page(struct page *page, unsigned long offset)
{
/* FIXME: we really should cancel any unstarted writes on this page */
return 1;
}
static int nfs_release_page(struct page *page, gfp_t gfp)
{
return !nfs_wb_page(page->mapping->host, page);
}
struct address_space_operations nfs_file_aops = {
.readpage = nfs_readpage,
.readpages = nfs_readpages,
.set_page_dirty = __set_page_dirty_nobuffers,
.writepage = nfs_writepage,
.writepages = nfs_writepages,
.prepare_write = nfs_prepare_write,
.commit_write = nfs_commit_write,
.invalidatepage = nfs_invalidate_page,
.releasepage = nfs_release_page,
#ifdef CONFIG_NFS_DIRECTIO
.direct_IO = nfs_direct_IO,
#endif
};
/*
* Write to a file (through the page cache).
*/
static ssize_t
nfs_file_write(struct kiocb *iocb, const char __user *buf, size_t count, loff_t pos)
{
struct dentry * dentry = iocb->ki_filp->f_dentry;
struct inode * inode = dentry->d_inode;
ssize_t result;
#ifdef CONFIG_NFS_DIRECTIO
if (iocb->ki_filp->f_flags & O_DIRECT)
return nfs_file_direct_write(iocb, buf, count, pos);
#endif
dfprintk(VFS, "nfs: 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);
result = -EBUSY;
if (IS_SWAPFILE(inode))
goto out_swapfile;
/*
* O_APPEND implies that we must revalidate the file length.
*/
if (iocb->ki_filp->f_flags & O_APPEND) {
result = nfs_revalidate_file_size(inode, iocb->ki_filp);
if (result)
goto out;
}
nfs_revalidate_mapping(inode, iocb->ki_filp->f_mapping);
result = count;
if (!count)
goto out;
result = generic_file_aio_write(iocb, buf, count, pos);
out:
return result;
out_swapfile:
printk(KERN_INFO "NFS: attempt to write to active swap file!\n");
goto out;
}
static int do_getlk(struct file *filp, int cmd, struct file_lock *fl)
{
struct file_lock *cfl;
struct inode *inode = filp->f_mapping->host;
int status = 0;
lock_kernel();
/* Try local locking first */
cfl = posix_test_lock(filp, fl);
if (cfl != NULL) {
locks_copy_lock(fl, cfl);
goto out;
}
if (nfs_have_delegation(inode, FMODE_READ))
goto out_noconflict;
if (NFS_SERVER(inode)->flags & NFS_MOUNT_NONLM)
goto out_noconflict;
status = NFS_PROTO(inode)->lock(filp, cmd, fl);
out:
unlock_kernel();
return status;
out_noconflict:
fl->fl_type = F_UNLCK;
goto out;
}
static int do_vfs_lock(struct file *file, struct file_lock *fl)
{
int res = 0;
switch (fl->fl_flags & (FL_POSIX|FL_FLOCK)) {
case FL_POSIX:
res = posix_lock_file_wait(file, fl);
break;
case FL_FLOCK:
res = flock_lock_file_wait(file, fl);
break;
default:
BUG();
}
if (res < 0)
printk(KERN_WARNING "%s: VFS is out of sync with lock manager!\n",
__FUNCTION__);
return res;
}
static int do_unlk(struct file *filp, int cmd, struct file_lock *fl)
{
struct inode *inode = filp->f_mapping->host;
sigset_t oldset;
int status;
rpc_clnt_sigmask(NFS_CLIENT(inode), &oldset);
/*
* Flush all pending writes before doing anything
* with locks..
*/
nfs_sync_mapping(filp->f_mapping);
/* NOTE: special case
* If we're signalled while cleaning up locks on process exit, we
* still need to complete the unlock.
*/
lock_kernel();
/* Use local locking if mounted with "-onolock" */
if (!(NFS_SERVER(inode)->flags & NFS_MOUNT_NONLM))
status = NFS_PROTO(inode)->lock(filp, cmd, fl);
else
status = do_vfs_lock(filp, fl);
unlock_kernel();
rpc_clnt_sigunmask(NFS_CLIENT(inode), &oldset);
return status;
}
static int do_setlk(struct file *filp, int cmd, struct file_lock *fl)
{
struct inode *inode = filp->f_mapping->host;
sigset_t oldset;
int status;
rpc_clnt_sigmask(NFS_CLIENT(inode), &oldset);
/*
* Flush all pending writes before doing anything
* with locks..
*/
status = nfs_sync_mapping(filp->f_mapping);
if (status != 0)
goto out;
lock_kernel();
/* Use local locking if mounted with "-onolock" */
if (!(NFS_SERVER(inode)->flags & NFS_MOUNT_NONLM)) {
status = NFS_PROTO(inode)->lock(filp, cmd, fl);
/* If we were signalled we still need to ensure that
* we clean up any state on the server. We therefore
* record the lock call as having succeeded in order to
* ensure that locks_remove_posix() cleans it out when
* the process exits.
*/
if (status == -EINTR || status == -ERESTARTSYS)
do_vfs_lock(filp, fl);
} else
status = do_vfs_lock(filp, fl);
unlock_kernel();
if (status < 0)
goto out;
/*
* Make sure we clear the cache whenever we try to get the lock.
* This makes locking act as a cache coherency point.
*/
nfs_sync_mapping(filp->f_mapping);
nfs_zap_caches(inode);
out:
rpc_clnt_sigunmask(NFS_CLIENT(inode), &oldset);
return status;
}
/*
* Lock a (portion of) a file
*/
static int nfs_lock(struct file *filp, int cmd, struct file_lock *fl)
{
struct inode * inode = filp->f_mapping->host;
dprintk("NFS: nfs_lock(f=%s/%ld, t=%x, fl=%x, r=%Ld:%Ld)\n",
inode->i_sb->s_id, inode->i_ino,
fl->fl_type, fl->fl_flags,
(long long)fl->fl_start, (long long)fl->fl_end);
if (!inode)
return -EINVAL;
/* No mandatory locks over NFS */
if ((inode->i_mode & (S_ISGID | S_IXGRP)) == S_ISGID &&
fl->fl_type != F_UNLCK)
return -ENOLCK;
if (IS_GETLK(cmd))
return do_getlk(filp, cmd, fl);
if (fl->fl_type == F_UNLCK)
return do_unlk(filp, cmd, fl);
return do_setlk(filp, cmd, fl);
}
/*
* Lock a (portion of) a file
*/
static int nfs_flock(struct file *filp, int cmd, struct file_lock *fl)
{
struct inode * inode = filp->f_mapping->host;
dprintk("NFS: nfs_flock(f=%s/%ld, t=%x, fl=%x)\n",
inode->i_sb->s_id, inode->i_ino,
fl->fl_type, fl->fl_flags);
if (!inode)
return -EINVAL;
/*
* No BSD flocks over NFS allowed.
* Note: we could try to fake a POSIX lock request here by
* using ((u32) filp | 0x80000000) or some such as the pid.
* Not sure whether that would be unique, though, or whether
* that would break in other places.
*/
if (!(fl->fl_flags & FL_FLOCK))
return -ENOLCK;
/* We're simulating flock() locks using posix locks on the server */
fl->fl_owner = (fl_owner_t)filp;
fl->fl_start = 0;
fl->fl_end = OFFSET_MAX;
if (fl->fl_type == F_UNLCK)
return do_unlk(filp, cmd, fl);
return do_setlk(filp, cmd, fl);
}