freebsd-dev/module/zfs/zpl_file.c
Etienne Dechamps cb2d19010d Support the fallocate() file operation.
Currently only the (FALLOC_FL_PUNCH_HOLE) flag combination is
supported, since it's the only one that matches the behavior of
zfs_space(). This makes it pretty much useless in its current
form, but it's a start.

To support other flag combinations we would need to modify
zfs_space() to make it more flexible, or emulate the desired
functionality in zpl_fallocate().

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #334
2012-02-09 16:19:32 -08:00

468 lines
12 KiB
C

/*
* CDDL HEADER START
*
* The contents of this file are subject to the terms of the
* Common Development and Distribution License (the "License").
* You may not use this file except in compliance with the License.
*
* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
* or http://www.opensolaris.org/os/licensing.
* See the License for the specific language governing permissions
* and limitations under the License.
*
* When distributing Covered Code, include this CDDL HEADER in each
* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
* If applicable, add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your own identifying
* information: Portions Copyright [yyyy] [name of copyright owner]
*
* CDDL HEADER END
*/
/*
* Copyright (c) 2011, Lawrence Livermore National Security, LLC.
*/
#include <sys/zfs_vfsops.h>
#include <sys/zfs_vnops.h>
#include <sys/zfs_znode.h>
#include <sys/zpl.h>
static int
zpl_open(struct inode *ip, struct file *filp)
{
cred_t *cr = CRED();
int error;
crhold(cr);
error = -zfs_open(ip, filp->f_mode, filp->f_flags, cr);
crfree(cr);
ASSERT3S(error, <=, 0);
if (error)
return (error);
return generic_file_open(ip, filp);
}
static int
zpl_release(struct inode *ip, struct file *filp)
{
cred_t *cr = CRED();
int error;
crhold(cr);
error = -zfs_close(ip, filp->f_flags, cr);
crfree(cr);
ASSERT3S(error, <=, 0);
return (error);
}
static int
zpl_readdir(struct file *filp, void *dirent, filldir_t filldir)
{
struct dentry *dentry = filp->f_path.dentry;
cred_t *cr = CRED();
int error;
crhold(cr);
error = -zfs_readdir(dentry->d_inode, dirent, filldir,
&filp->f_pos, cr);
crfree(cr);
ASSERT3S(error, <=, 0);
return (error);
}
#if defined(HAVE_FSYNC_WITH_DENTRY)
/*
* Linux 2.6.x - 2.6.34 API,
* Through 2.6.34 the nfsd kernel server would pass a NULL 'file struct *'
* to the fops->fsync() hook. For this reason, we must be careful not to
* use filp unconditionally.
*/
static int
zpl_fsync(struct file *filp, struct dentry *dentry, int datasync)
{
cred_t *cr = CRED();
int error;
crhold(cr);
error = -zfs_fsync(dentry->d_inode, datasync, cr);
crfree(cr);
ASSERT3S(error, <=, 0);
return (error);
}
#elif defined(HAVE_FSYNC_WITHOUT_DENTRY)
/*
* Linux 2.6.35 - 3.0 API,
* As of 2.6.35 the dentry argument to the fops->fsync() hook was deemed
* redundant. The dentry is still accessible via filp->f_path.dentry,
* and we are guaranteed that filp will never be NULL.
*/
static int
zpl_fsync(struct file *filp, int datasync)
{
struct inode *inode = filp->f_mapping->host;
cred_t *cr = CRED();
int error;
crhold(cr);
error = -zfs_fsync(inode, datasync, cr);
crfree(cr);
ASSERT3S(error, <=, 0);
return (error);
}
#elif defined(HAVE_FSYNC_RANGE)
/*
* Linux 3.1 - 3.x API,
* As of 3.1 the responsibility to call filemap_write_and_wait_range() has
* been pushed down in to the .fsync() vfs hook. Additionally, the i_mutex
* lock is no longer held by the caller, for zfs we don't require the lock
* to be held so we don't acquire it.
*/
static int
zpl_fsync(struct file *filp, loff_t start, loff_t end, int datasync)
{
struct inode *inode = filp->f_mapping->host;
cred_t *cr = CRED();
int error;
error = filemap_write_and_wait_range(inode->i_mapping, start, end);
if (error)
return (error);
crhold(cr);
error = -zfs_fsync(inode, datasync, cr);
crfree(cr);
ASSERT3S(error, <=, 0);
return (error);
}
#else
#error "Unsupported fops->fsync() implementation"
#endif
ssize_t
zpl_read_common(struct inode *ip, const char *buf, size_t len, loff_t pos,
uio_seg_t segment, int flags, cred_t *cr)
{
int error;
struct iovec iov;
uio_t uio;
iov.iov_base = (void *)buf;
iov.iov_len = len;
uio.uio_iov = &iov;
uio.uio_resid = len;
uio.uio_iovcnt = 1;
uio.uio_loffset = pos;
uio.uio_limit = MAXOFFSET_T;
uio.uio_segflg = segment;
error = -zfs_read(ip, &uio, flags, cr);
if (error < 0)
return (error);
return (len - uio.uio_resid);
}
static ssize_t
zpl_read(struct file *filp, char __user *buf, size_t len, loff_t *ppos)
{
cred_t *cr = CRED();
ssize_t read;
crhold(cr);
read = zpl_read_common(filp->f_mapping->host, buf, len, *ppos,
UIO_USERSPACE, filp->f_flags, cr);
crfree(cr);
if (read < 0)
return (read);
*ppos += read;
return (read);
}
ssize_t
zpl_write_common(struct inode *ip, const char *buf, size_t len, loff_t pos,
uio_seg_t segment, int flags, cred_t *cr)
{
int error;
struct iovec iov;
uio_t uio;
iov.iov_base = (void *)buf;
iov.iov_len = len;
uio.uio_iov = &iov;
uio.uio_resid = len,
uio.uio_iovcnt = 1;
uio.uio_loffset = pos;
uio.uio_limit = MAXOFFSET_T;
uio.uio_segflg = segment;
error = -zfs_write(ip, &uio, flags, cr);
if (error < 0)
return (error);
return (len - uio.uio_resid);
}
static ssize_t
zpl_write(struct file *filp, const char __user *buf, size_t len, loff_t *ppos)
{
cred_t *cr = CRED();
ssize_t wrote;
crhold(cr);
wrote = zpl_write_common(filp->f_mapping->host, buf, len, *ppos,
UIO_USERSPACE, filp->f_flags, cr);
crfree(cr);
if (wrote < 0)
return (wrote);
*ppos += wrote;
return (wrote);
}
/*
* It's worth taking a moment to describe how mmap is implemented
* for zfs because it differs considerably from other Linux filesystems.
* However, this issue is handled the same way under OpenSolaris.
*
* The issue is that by design zfs bypasses the Linux page cache and
* leaves all caching up to the ARC. This has been shown to work
* well for the common read(2)/write(2) case. However, mmap(2)
* is problem because it relies on being tightly integrated with the
* page cache. To handle this we cache mmap'ed files twice, once in
* the ARC and a second time in the page cache. The code is careful
* to keep both copies synchronized.
*
* When a file with an mmap'ed region is written to using write(2)
* both the data in the ARC and existing pages in the page cache
* are updated. For a read(2) data will be read first from the page
* cache then the ARC if needed. Neither a write(2) or read(2) will
* will ever result in new pages being added to the page cache.
*
* New pages are added to the page cache only via .readpage() which
* is called when the vfs needs to read a page off disk to back the
* virtual memory region. These pages may be modified without
* notifying the ARC and will be written out periodically via
* .writepage(). This will occur due to either a sync or the usual
* page aging behavior. Note because a read(2) of a mmap'ed file
* will always check the page cache first even when the ARC is out
* of date correct data will still be returned.
*
* While this implementation ensures correct behavior it does have
* have some drawbacks. The most obvious of which is that it
* increases the required memory footprint when access mmap'ed
* files. It also adds additional complexity to the code keeping
* both caches synchronized.
*
* Longer term it may be possible to cleanly resolve this wart by
* mapping page cache pages directly on to the ARC buffers. The
* Linux address space operations are flexible enough to allow
* selection of which pages back a particular index. The trick
* would be working out the details of which subsystem is in
* charge, the ARC, the page cache, or both. It may also prove
* helpful to move the ARC buffers to a scatter-gather lists
* rather than a vmalloc'ed region.
*/
static int
zpl_mmap(struct file *filp, struct vm_area_struct *vma)
{
struct inode *ip = filp->f_mapping->host;
znode_t *zp = ITOZ(ip);
int error;
error = -zfs_map(ip, vma->vm_pgoff, (caddr_t *)vma->vm_start,
(size_t)(vma->vm_end - vma->vm_start), vma->vm_flags);
if (error)
return (error);
error = generic_file_mmap(filp, vma);
if (error)
return (error);
mutex_enter(&zp->z_lock);
zp->z_is_mapped = 1;
mutex_exit(&zp->z_lock);
return (error);
}
/*
* Populate a page with data for the Linux page cache. This function is
* only used to support mmap(2). There will be an identical copy of the
* data in the ARC which is kept up to date via .write() and .writepage().
*
* Current this function relies on zpl_read_common() and the O_DIRECT
* flag to read in a page. This works but the more correct way is to
* update zfs_fillpage() to be Linux friendly and use that interface.
*/
static int
zpl_readpage(struct file *filp, struct page *pp)
{
struct inode *ip;
struct page *pl[1];
int error = 0;
ASSERT(PageLocked(pp));
ip = pp->mapping->host;
pl[0] = pp;
error = -zfs_getpage(ip, pl, 1);
if (error) {
SetPageError(pp);
ClearPageUptodate(pp);
} else {
ClearPageError(pp);
SetPageUptodate(pp);
flush_dcache_page(pp);
}
unlock_page(pp);
return error;
}
/*
* Populate a set of pages with data for the Linux page cache. This
* function will only be called for read ahead and never for demand
* paging. For simplicity, the code relies on read_cache_pages() to
* correctly lock each page for IO and call zpl_readpage().
*/
static int
zpl_readpages(struct file *filp, struct address_space *mapping,
struct list_head *pages, unsigned nr_pages)
{
return (read_cache_pages(mapping, pages,
(filler_t *)zpl_readpage, filp));
}
int
zpl_putpage(struct page *pp, struct writeback_control *wbc, void *data)
{
struct address_space *mapping = data;
ASSERT(PageLocked(pp));
ASSERT(!PageWriteback(pp));
/*
* Disable the normal reclaim path for zpl_putpage(). This
* ensures that all memory allocations under this call path
* will never enter direct reclaim. If this were to happen
* the VM might try to write out additional pages by calling
* zpl_putpage() again resulting in a deadlock.
*/
if (current->flags & PF_MEMALLOC) {
(void) zfs_putpage(mapping->host, pp, wbc);
} else {
current->flags |= PF_MEMALLOC;
(void) zfs_putpage(mapping->host, pp, wbc);
current->flags &= ~PF_MEMALLOC;
}
return (0);
}
static int
zpl_writepages(struct address_space *mapping, struct writeback_control *wbc)
{
return write_cache_pages(mapping, wbc, zpl_putpage, mapping);
}
/*
* Write out dirty pages to the ARC, this function is only required to
* support mmap(2). Mapped pages may be dirtied by memory operations
* which never call .write(). These dirty pages are kept in sync with
* the ARC buffers via this hook.
*/
static int
zpl_writepage(struct page *pp, struct writeback_control *wbc)
{
return zpl_putpage(pp, wbc, pp->mapping);
}
/*
* The only flag combination which matches the behavior of zfs_space()
* is FALLOC_FL_PUNCH_HOLE. This flag was introduced in the 2.6.38 kernel.
*/
long
zpl_fallocate_common(struct inode *ip, int mode, loff_t offset, loff_t len)
{
cred_t *cr = CRED();
int error = -EOPNOTSUPP;
if (mode & FALLOC_FL_KEEP_SIZE)
return (-EOPNOTSUPP);
crhold(cr);
#ifdef FALLOC_FL_PUNCH_HOLE
if (mode & FALLOC_FL_PUNCH_HOLE) {
flock64_t bf;
bf.l_type = F_WRLCK;
bf.l_whence = 0;
bf.l_start = offset;
bf.l_len = len;
bf.l_pid = 0;
error = -zfs_space(ip, F_FREESP, &bf, FWRITE, offset, cr);
}
#endif /* FALLOC_FL_PUNCH_HOLE */
crfree(cr);
ASSERT3S(error, <=, 0);
return (error);
}
#ifdef HAVE_FILE_FALLOCATE
static long
zpl_fallocate(struct file *filp, int mode, loff_t offset, loff_t len)
{
return zpl_fallocate_common(filp->f_path.dentry->d_inode,
mode, offset, len);
}
#endif /* HAVE_FILE_FALLOCATE */
const struct address_space_operations zpl_address_space_operations = {
.readpages = zpl_readpages,
.readpage = zpl_readpage,
.writepage = zpl_writepage,
.writepages = zpl_writepages,
};
const struct file_operations zpl_file_operations = {
.open = zpl_open,
.release = zpl_release,
.llseek = generic_file_llseek,
.read = zpl_read,
.write = zpl_write,
.readdir = zpl_readdir,
.mmap = zpl_mmap,
.fsync = zpl_fsync,
#ifdef HAVE_FILE_FALLOCATE
.fallocate = zpl_fallocate,
#endif /* HAVE_FILE_FALLOCATE */
};
const struct file_operations zpl_dir_file_operations = {
.llseek = generic_file_llseek,
.read = generic_read_dir,
.readdir = zpl_readdir,
.fsync = zpl_fsync,
};