linux-stable/fs/9p/vfs_addr.c
Dominique Martinet b48dbb998d 9p fid refcount: add p9_fid_get/put wrappers
I was recently reminded that it is not clear that p9_client_clunk()
was actually just decrementing refcount and clunking only when that
reaches zero: make it clear through a set of helpers.

This will also allow instrumenting refcounting better for debugging
next patch

Link: https://lkml.kernel.org/r/20220612085330.1451496-5-asmadeus@codewreck.org
Reviewed-by: Tyler Hicks <tyhicks@linux.microsoft.com>
Reviewed-by: Christian Schoenebeck <linux_oss@crudebyte.com>
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>
2022-07-02 18:52:21 +09:00

360 lines
9.3 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/*
* This file contians vfs address (mmap) ops for 9P2000.
*
* Copyright (C) 2005 by Eric Van Hensbergen <ericvh@gmail.com>
* Copyright (C) 2002 by Ron Minnich <rminnich@lanl.gov>
*/
#include <linux/module.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/stat.h>
#include <linux/string.h>
#include <linux/inet.h>
#include <linux/pagemap.h>
#include <linux/idr.h>
#include <linux/sched.h>
#include <linux/swap.h>
#include <linux/uio.h>
#include <linux/netfs.h>
#include <net/9p/9p.h>
#include <net/9p/client.h>
#include "v9fs.h"
#include "v9fs_vfs.h"
#include "cache.h"
#include "fid.h"
/**
* v9fs_issue_read - Issue a read from 9P
* @subreq: The read to make
*/
static void v9fs_issue_read(struct netfs_io_subrequest *subreq)
{
struct netfs_io_request *rreq = subreq->rreq;
struct p9_fid *fid = rreq->netfs_priv;
struct iov_iter to;
loff_t pos = subreq->start + subreq->transferred;
size_t len = subreq->len - subreq->transferred;
int total, err;
iov_iter_xarray(&to, READ, &rreq->mapping->i_pages, pos, len);
total = p9_client_read(fid, pos, &to, &err);
/* if we just extended the file size, any portion not in
* cache won't be on server and is zeroes */
__set_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags);
netfs_subreq_terminated(subreq, err ?: total, false);
}
/**
* v9fs_init_request - Initialise a read request
* @rreq: The read request
* @file: The file being read from
*/
static int v9fs_init_request(struct netfs_io_request *rreq, struct file *file)
{
struct inode *inode = file_inode(file);
struct v9fs_inode *v9inode = V9FS_I(inode);
struct p9_fid *fid = file->private_data;
BUG_ON(!fid);
/* we might need to read from a fid that was opened write-only
* for read-modify-write of page cache, use the writeback fid
* for that */
if (rreq->origin == NETFS_READ_FOR_WRITE &&
(fid->mode & O_ACCMODE) == O_WRONLY) {
fid = v9inode->writeback_fid;
BUG_ON(!fid);
}
p9_fid_get(fid);
rreq->netfs_priv = fid;
return 0;
}
/**
* v9fs_free_request - Cleanup request initialized by v9fs_init_rreq
* @rreq: The I/O request to clean up
*/
static void v9fs_free_request(struct netfs_io_request *rreq)
{
struct p9_fid *fid = rreq->netfs_priv;
p9_fid_put(fid);
}
/**
* v9fs_begin_cache_operation - Begin a cache operation for a read
* @rreq: The read request
*/
static int v9fs_begin_cache_operation(struct netfs_io_request *rreq)
{
#ifdef CONFIG_9P_FSCACHE
struct fscache_cookie *cookie = v9fs_inode_cookie(V9FS_I(rreq->inode));
return fscache_begin_read_operation(&rreq->cache_resources, cookie);
#else
return -ENOBUFS;
#endif
}
const struct netfs_request_ops v9fs_req_ops = {
.init_request = v9fs_init_request,
.free_request = v9fs_free_request,
.begin_cache_operation = v9fs_begin_cache_operation,
.issue_read = v9fs_issue_read,
};
/**
* v9fs_release_folio - release the private state associated with a folio
* @folio: The folio to be released
* @gfp: The caller's allocation restrictions
*
* Returns true if the page can be released, false otherwise.
*/
static bool v9fs_release_folio(struct folio *folio, gfp_t gfp)
{
struct inode *inode = folio_inode(folio);
if (folio_test_private(folio))
return false;
#ifdef CONFIG_9P_FSCACHE
if (folio_test_fscache(folio)) {
if (current_is_kswapd() || !(gfp & __GFP_FS))
return false;
folio_wait_fscache(folio);
}
#endif
fscache_note_page_release(v9fs_inode_cookie(V9FS_I(inode)));
return true;
}
static void v9fs_invalidate_folio(struct folio *folio, size_t offset,
size_t length)
{
folio_wait_fscache(folio);
}
static void v9fs_write_to_cache_done(void *priv, ssize_t transferred_or_error,
bool was_async)
{
struct v9fs_inode *v9inode = priv;
__le32 version;
if (IS_ERR_VALUE(transferred_or_error) &&
transferred_or_error != -ENOBUFS) {
version = cpu_to_le32(v9inode->qid.version);
fscache_invalidate(v9fs_inode_cookie(v9inode), &version,
i_size_read(&v9inode->netfs.inode), 0);
}
}
static int v9fs_vfs_write_folio_locked(struct folio *folio)
{
struct inode *inode = folio_inode(folio);
struct v9fs_inode *v9inode = V9FS_I(inode);
struct fscache_cookie *cookie = v9fs_inode_cookie(v9inode);
loff_t start = folio_pos(folio);
loff_t i_size = i_size_read(inode);
struct iov_iter from;
size_t len = folio_size(folio);
int err;
if (start >= i_size)
return 0; /* Simultaneous truncation occurred */
len = min_t(loff_t, i_size - start, len);
iov_iter_xarray(&from, WRITE, &folio_mapping(folio)->i_pages, start, len);
/* We should have writeback_fid always set */
BUG_ON(!v9inode->writeback_fid);
folio_wait_fscache(folio);
folio_start_writeback(folio);
p9_client_write(v9inode->writeback_fid, start, &from, &err);
if (err == 0 &&
fscache_cookie_enabled(cookie) &&
test_bit(FSCACHE_COOKIE_IS_CACHING, &cookie->flags)) {
folio_start_fscache(folio);
fscache_write_to_cache(v9fs_inode_cookie(v9inode),
folio_mapping(folio), start, len, i_size,
v9fs_write_to_cache_done, v9inode,
true);
}
folio_end_writeback(folio);
return err;
}
static int v9fs_vfs_writepage(struct page *page, struct writeback_control *wbc)
{
struct folio *folio = page_folio(page);
int retval;
p9_debug(P9_DEBUG_VFS, "folio %p\n", folio);
retval = v9fs_vfs_write_folio_locked(folio);
if (retval < 0) {
if (retval == -EAGAIN) {
folio_redirty_for_writepage(wbc, folio);
retval = 0;
} else {
mapping_set_error(folio_mapping(folio), retval);
}
} else
retval = 0;
folio_unlock(folio);
return retval;
}
static int v9fs_launder_folio(struct folio *folio)
{
int retval;
if (folio_clear_dirty_for_io(folio)) {
retval = v9fs_vfs_write_folio_locked(folio);
if (retval)
return retval;
}
folio_wait_fscache(folio);
return 0;
}
/**
* v9fs_direct_IO - 9P address space operation for direct I/O
* @iocb: target I/O control block
* @iter: The data/buffer to use
*
* The presence of v9fs_direct_IO() in the address space ops vector
* allowes open() O_DIRECT flags which would have failed otherwise.
*
* In the non-cached mode, we shunt off direct read and write requests before
* the VFS gets them, so this method should never be called.
*
* Direct IO is not 'yet' supported in the cached mode. Hence when
* this routine is called through generic_file_aio_read(), the read/write fails
* with an error.
*
*/
static ssize_t
v9fs_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
{
struct file *file = iocb->ki_filp;
loff_t pos = iocb->ki_pos;
ssize_t n;
int err = 0;
if (iov_iter_rw(iter) == WRITE) {
n = p9_client_write(file->private_data, pos, iter, &err);
if (n) {
struct inode *inode = file_inode(file);
loff_t i_size = i_size_read(inode);
if (pos + n > i_size)
inode_add_bytes(inode, pos + n - i_size);
}
} else {
n = p9_client_read(file->private_data, pos, iter, &err);
}
return n ? n : err;
}
static int v9fs_write_begin(struct file *filp, struct address_space *mapping,
loff_t pos, unsigned int len,
struct page **subpagep, void **fsdata)
{
int retval;
struct folio *folio;
struct v9fs_inode *v9inode = V9FS_I(mapping->host);
p9_debug(P9_DEBUG_VFS, "filp %p, mapping %p\n", filp, mapping);
BUG_ON(!v9inode->writeback_fid);
/* Prefetch area to be written into the cache if we're caching this
* file. We need to do this before we get a lock on the page in case
* there's more than one writer competing for the same cache block.
*/
retval = netfs_write_begin(&v9inode->netfs, filp, mapping, pos, len, &folio, fsdata);
if (retval < 0)
return retval;
*subpagep = &folio->page;
return retval;
}
static int v9fs_write_end(struct file *filp, struct address_space *mapping,
loff_t pos, unsigned int len, unsigned int copied,
struct page *subpage, void *fsdata)
{
loff_t last_pos = pos + copied;
struct folio *folio = page_folio(subpage);
struct inode *inode = mapping->host;
struct v9fs_inode *v9inode = V9FS_I(inode);
p9_debug(P9_DEBUG_VFS, "filp %p, mapping %p\n", filp, mapping);
if (!folio_test_uptodate(folio)) {
if (unlikely(copied < len)) {
copied = 0;
goto out;
}
folio_mark_uptodate(folio);
}
/*
* No need to use i_size_read() here, the i_size
* cannot change under us because we hold the i_mutex.
*/
if (last_pos > inode->i_size) {
inode_add_bytes(inode, last_pos - inode->i_size);
i_size_write(inode, last_pos);
fscache_update_cookie(v9fs_inode_cookie(v9inode), NULL, &last_pos);
}
folio_mark_dirty(folio);
out:
folio_unlock(folio);
folio_put(folio);
return copied;
}
#ifdef CONFIG_9P_FSCACHE
/*
* Mark a page as having been made dirty and thus needing writeback. We also
* need to pin the cache object to write back to.
*/
static bool v9fs_dirty_folio(struct address_space *mapping, struct folio *folio)
{
struct v9fs_inode *v9inode = V9FS_I(mapping->host);
return fscache_dirty_folio(mapping, folio, v9fs_inode_cookie(v9inode));
}
#else
#define v9fs_dirty_folio filemap_dirty_folio
#endif
const struct address_space_operations v9fs_addr_operations = {
.read_folio = netfs_read_folio,
.readahead = netfs_readahead,
.dirty_folio = v9fs_dirty_folio,
.writepage = v9fs_vfs_writepage,
.write_begin = v9fs_write_begin,
.write_end = v9fs_write_end,
.release_folio = v9fs_release_folio,
.invalidate_folio = v9fs_invalidate_folio,
.launder_folio = v9fs_launder_folio,
.direct_IO = v9fs_direct_IO,
};