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9p: Convert to using the netfs helper lib to do reads and caching

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Convert the 9p filesystem to use the netfs helper lib to handle readpage,
readahead and write_begin, converting those into a common issue_op for the
filesystem itself to handle.  The netfs helper lib also handles reading
from fscache if a cache is available, and interleaving reads from both
sources.

This change also switches from the old fscache I/O API to the new one,
meaning that fscache no longer keeps track of netfs pages and instead does
async DIO between the backing files and the 9p file pagecache.  As a part
of this change, the handling of PG_fscache changes.  It now just means that
the cache has a write I/O operation in progress on a page (PG_locked
is used for a read I/O op).

Note that this is a cut-down version of the fscache rewrite and does not
change any of the cookie and cache coherency handling.

Changes
=======
ver #4:
  - Rebase on top of folios.
  - Don't use wait_on_page_bit_killable().

ver #3:
  - v9fs_req_issue_op() needs to terminate the subrequest.
  - v9fs_write_end() needs to call SetPageUptodate() a bit more often.
  - It's not CONFIG_{AFS,V9FS}_FSCACHE[1]
  - v9fs_init_rreq() should take a ref on the p9_fid and the cleanup should
    drop it [from Dominique Martinet].

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-and-tested-by: Dominique Martinet <asmadeus@codewreck.org>
cc: v9fs-developer@lists.sourceforge.net
cc: linux-cachefs@redhat.com
Link: https://lore.kernel.org/r/YUm+xucHxED+1MJp@codewreck.org/ [1]
Link: https://lore.kernel.org/r/163162772646.438332.16323773205855053535.stgit@warthog.procyon.org.uk/ # rfc
Link: https://lore.kernel.org/r/163189109885.2509237.7153668924503399173.stgit@warthog.procyon.org.uk/ # rfc v2
Link: https://lore.kernel.org/r/163363943896.1980952.1226527304649419689.stgit@warthog.procyon.org.uk/ # v3
Link: https://lore.kernel.org/r/163551662876.1877519.14706391695553204156.stgit@warthog.procyon.org.uk/ # v4
Link: https://lore.kernel.org/r/163584179557.4023316.11089762304657644342.stgit@warthog.procyon.org.uk # rebase on folio
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>
This commit is contained in:
David Howells 2021-11-02 08:29:55 +00:00 committed by Dominique Martinet
parent 0dc54bd4d6
commit eb497943fa
6 changed files with 128 additions and 340 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

1
fs/9p/Kconfig
View file

@ -2,6 +2,7 @@
config 9P_FS
tristate "Plan 9 Resource Sharing Support (9P2000)"
depends on INET && NET_9P
select NETFS_SUPPORT
help
If you say Y here, you will get experimental support for
Plan 9 resource sharing via the 9P2000 protocol.

137
fs/9p/cache.c
View file

@ -199,140 +199,3 @@ void v9fs_cache_inode_reset_cookie(struct inode *inode)
mutex_unlock(&v9inode->fscache_lock);
}
int __v9fs_fscache_release_page(struct page *page, gfp_t gfp)
{
struct inode *inode = page->mapping->host;
struct v9fs_inode *v9inode = V9FS_I(inode);
BUG_ON(!v9inode->fscache);
return fscache_maybe_release_page(v9inode->fscache, page, gfp);
}
void __v9fs_fscache_invalidate_page(struct page *page)
{
struct inode *inode = page->mapping->host;
struct v9fs_inode *v9inode = V9FS_I(inode);
BUG_ON(!v9inode->fscache);
if (PageFsCache(page)) {
fscache_wait_on_page_write(v9inode->fscache, page);
BUG_ON(!PageLocked(page));
fscache_uncache_page(v9inode->fscache, page);
}
}
static void v9fs_vfs_readpage_complete(struct page *page, void *data,
int error)
{
if (!error)
SetPageUptodate(page);
unlock_page(page);
}
/*
* __v9fs_readpage_from_fscache - read a page from cache
*
* Returns 0 if the pages are in cache and a BIO is submitted,
* 1 if the pages are not in cache and -error otherwise.
*/
int __v9fs_readpage_from_fscache(struct inode *inode, struct page *page)
{
int ret;
const struct v9fs_inode *v9inode = V9FS_I(inode);
p9_debug(P9_DEBUG_FSC, "inode %p page %p\n", inode, page);
if (!v9inode->fscache)
return -ENOBUFS;
ret = fscache_read_or_alloc_page(v9inode->fscache,
page,
v9fs_vfs_readpage_complete,
NULL,
GFP_KERNEL);
switch (ret) {
case -ENOBUFS:
case -ENODATA:
p9_debug(P9_DEBUG_FSC, "page/inode not in cache %d\n", ret);
return 1;
case 0:
p9_debug(P9_DEBUG_FSC, "BIO submitted\n");
return ret;
default:
p9_debug(P9_DEBUG_FSC, "ret %d\n", ret);
return ret;
}
}
/*
* __v9fs_readpages_from_fscache - read multiple pages from cache
*
* Returns 0 if the pages are in cache and a BIO is submitted,
* 1 if the pages are not in cache and -error otherwise.
*/
int __v9fs_readpages_from_fscache(struct inode *inode,
struct address_space *mapping,
struct list_head *pages,
unsigned *nr_pages)
{
int ret;
const struct v9fs_inode *v9inode = V9FS_I(inode);
p9_debug(P9_DEBUG_FSC, "inode %p pages %u\n", inode, *nr_pages);
if (!v9inode->fscache)
return -ENOBUFS;
ret = fscache_read_or_alloc_pages(v9inode->fscache,
mapping, pages, nr_pages,
v9fs_vfs_readpage_complete,
NULL,
mapping_gfp_mask(mapping));
switch (ret) {
case -ENOBUFS:
case -ENODATA:
p9_debug(P9_DEBUG_FSC, "pages/inodes not in cache %d\n", ret);
return 1;
case 0:
BUG_ON(!list_empty(pages));
BUG_ON(*nr_pages != 0);
p9_debug(P9_DEBUG_FSC, "BIO submitted\n");
return ret;
default:
p9_debug(P9_DEBUG_FSC, "ret %d\n", ret);
return ret;
}
}
/*
* __v9fs_readpage_to_fscache - write a page to the cache
*
*/
void __v9fs_readpage_to_fscache(struct inode *inode, struct page *page)
{
int ret;
const struct v9fs_inode *v9inode = V9FS_I(inode);
p9_debug(P9_DEBUG_FSC, "inode %p page %p\n", inode, page);
ret = fscache_write_page(v9inode->fscache, page,
i_size_read(&v9inode->vfs_inode), GFP_KERNEL);
p9_debug(P9_DEBUG_FSC, "ret = %d\n", ret);
if (ret != 0)
v9fs_uncache_page(inode, page);
}
/*
* wait for a page to complete writing to the cache
*/
void __v9fs_fscache_wait_on_page_write(struct inode *inode, struct page *page)
{
const struct v9fs_inode *v9inode = V9FS_I(inode);
p9_debug(P9_DEBUG_FSC, "inode %p page %p\n", inode, page);
if (PageFsCache(page))
fscache_wait_on_page_write(v9inode->fscache, page);
}

97
fs/9p/cache.h
View file

@ -7,9 +7,10 @@
#ifndef _9P_CACHE_H
#define _9P_CACHE_H
#ifdef CONFIG_9P_FSCACHE
#define FSCACHE_USE_NEW_IO_API
#include <linux/fscache.h>
#include <linux/spinlock.h>
#ifdef CONFIG_9P_FSCACHE
extern struct fscache_netfs v9fs_cache_netfs;
extern const struct fscache_cookie_def v9fs_cache_session_index_def;
@ -27,64 +28,6 @@ extern void v9fs_cache_inode_reset_cookie(struct inode *inode);
extern int __v9fs_cache_register(void);
extern void __v9fs_cache_unregister(void);
extern int __v9fs_fscache_release_page(struct page *page, gfp_t gfp);
extern void __v9fs_fscache_invalidate_page(struct page *page);
extern int __v9fs_readpage_from_fscache(struct inode *inode,
struct page *page);
extern int __v9fs_readpages_from_fscache(struct inode *inode,
struct address_space *mapping,
struct list_head *pages,
unsigned *nr_pages);
extern void __v9fs_readpage_to_fscache(struct inode *inode, struct page *page);
extern void __v9fs_fscache_wait_on_page_write(struct inode *inode,
struct page *page);
static inline int v9fs_fscache_release_page(struct page *page,
gfp_t gfp)
{
return __v9fs_fscache_release_page(page, gfp);
}
static inline void v9fs_fscache_invalidate_page(struct page *page)
{
__v9fs_fscache_invalidate_page(page);
}
static inline int v9fs_readpage_from_fscache(struct inode *inode,
struct page *page)
{
return __v9fs_readpage_from_fscache(inode, page);
}
static inline int v9fs_readpages_from_fscache(struct inode *inode,
struct address_space *mapping,
struct list_head *pages,
unsigned *nr_pages)
{
return __v9fs_readpages_from_fscache(inode, mapping, pages,
nr_pages);
}
static inline void v9fs_readpage_to_fscache(struct inode *inode,
struct page *page)
{
if (PageFsCache(page))
__v9fs_readpage_to_fscache(inode, page);
}
static inline void v9fs_uncache_page(struct inode *inode, struct page *page)
{
struct v9fs_inode *v9inode = V9FS_I(inode);
fscache_uncache_page(v9inode->fscache, page);
BUG_ON(PageFsCache(page));
}
static inline void v9fs_fscache_wait_on_page_write(struct inode *inode,
struct page *page)
{
return __v9fs_fscache_wait_on_page_write(inode, page);
}
#else /* CONFIG_9P_FSCACHE */
static inline void v9fs_cache_inode_get_cookie(struct inode *inode)
@ -99,39 +42,5 @@ static inline void v9fs_cache_inode_set_cookie(struct inode *inode, struct file
{
}
static inline int v9fs_fscache_release_page(struct page *page,
gfp_t gfp) {
return 1;
}
static inline void v9fs_fscache_invalidate_page(struct page *page) {}
static inline int v9fs_readpage_from_fscache(struct inode *inode,
struct page *page)
{
return -ENOBUFS;
}
static inline int v9fs_readpages_from_fscache(struct inode *inode,
struct address_space *mapping,
struct list_head *pages,
unsigned *nr_pages)
{
return -ENOBUFS;
}
static inline void v9fs_readpage_to_fscache(struct inode *inode,
struct page *page)
{}
static inline void v9fs_uncache_page(struct inode *inode, struct page *page)
{}
static inline void v9fs_fscache_wait_on_page_write(struct inode *inode,
struct page *page)
{
return;
}
#endif /* CONFIG_9P_FSCACHE */
#endif /* _9P_CACHE_H */

9
fs/9p/v9fs.h
View file

@ -124,6 +124,15 @@ static inline struct v9fs_inode *V9FS_I(const struct inode *inode)
return container_of(inode, struct v9fs_inode, vfs_inode);
}
static inline struct fscache_cookie *v9fs_inode_cookie(struct v9fs_inode *v9inode)
{
#ifdef CONFIG_9P_FSCACHE
return v9inode->fscache;
#else
return NULL;
#endif
}
extern int v9fs_show_options(struct seq_file *m, struct dentry *root);
struct p9_fid *v9fs_session_init(struct v9fs_session_info *, const char *,

207
fs/9p/vfs_addr.c
View file

@ -19,7 +19,7 @@
#include <linux/idr.h>
#include <linux/sched.h>
#include <linux/uio.h>
#include <linux/bvec.h>
#include <linux/netfs.h>
#include <net/9p/9p.h>
#include <net/9p/client.h>
@ -29,88 +29,97 @@
#include "fid.h"
/**
* v9fs_fid_readpage - read an entire page in from 9P
* @data: Opaque pointer to the fid being read
* @page: structure to page
*
* v9fs_req_issue_op - Issue a read from 9P
* @subreq: The read to make
*/
static int v9fs_fid_readpage(void *data, struct page *page)
static void v9fs_req_issue_op(struct netfs_read_subrequest *subreq)
{
struct p9_fid *fid = data;
struct inode *inode = page->mapping->host;
struct bio_vec bvec = {.bv_page = page, .bv_len = PAGE_SIZE};
struct netfs_read_request *rreq = subreq->rreq;
struct p9_fid *fid = rreq->netfs_priv;
struct iov_iter to;
int retval, err;
loff_t pos = subreq->start + subreq->transferred;
size_t len = subreq->len - subreq->transferred;
int total, err;
p9_debug(P9_DEBUG_VFS, "\n");
iov_iter_xarray(&to, READ, &rreq->mapping->i_pages, pos, len);
BUG_ON(!PageLocked(page));
retval = v9fs_readpage_from_fscache(inode, page);
if (retval == 0)
return retval;
iov_iter_bvec(&to, READ, &bvec, 1, PAGE_SIZE);
retval = p9_client_read(fid, page_offset(page), &to, &err);
if (err) {
v9fs_uncache_page(inode, page);
retval = err;
goto done;
}
zero_user(page, retval, PAGE_SIZE - retval);
flush_dcache_page(page);
SetPageUptodate(page);
v9fs_readpage_to_fscache(inode, page);
retval = 0;
done:
unlock_page(page);
return retval;
total = p9_client_read(fid, pos, &to, &err);
netfs_subreq_terminated(subreq, err ?: total, false);
}
/**
* v9fs_init_rreq - Initialise a read request
* @rreq: The read request
* @file: The file being read from
*/
static void v9fs_init_rreq(struct netfs_read_request *rreq, struct file *file)
{
struct p9_fid *fid = file->private_data;
refcount_inc(&fid->count);
rreq->netfs_priv = fid;
}
/**
* v9fs_req_cleanup - Cleanup request initialized by v9fs_init_rreq
* @mapping: unused mapping of request to cleanup
* @priv: private data to cleanup, a fid, guaranted non-null.
*/
static void v9fs_req_cleanup(struct address_space *mapping, void *priv)
{
struct p9_fid *fid = priv;
p9_client_clunk(fid);
}
/**
* v9fs_is_cache_enabled - Determine if caching is enabled for an inode
* @inode: The inode to check
*/
static bool v9fs_is_cache_enabled(struct inode *inode)
{
struct fscache_cookie *cookie = v9fs_inode_cookie(V9FS_I(inode));
return fscache_cookie_enabled(cookie) && !hlist_empty(&cookie->backing_objects);
}
/**
* v9fs_begin_cache_operation - Begin a cache operation for a read
* @rreq: The read request
*/
static int v9fs_begin_cache_operation(struct netfs_read_request *rreq)
{
struct fscache_cookie *cookie = v9fs_inode_cookie(V9FS_I(rreq->inode));
return fscache_begin_read_operation(rreq, cookie);
}
static const struct netfs_read_request_ops v9fs_req_ops = {
.init_rreq = v9fs_init_rreq,
.is_cache_enabled = v9fs_is_cache_enabled,
.begin_cache_operation = v9fs_begin_cache_operation,
.issue_op = v9fs_req_issue_op,
.cleanup = v9fs_req_cleanup,
};
/**
* v9fs_vfs_readpage - read an entire page in from 9P
*
* @filp: file being read
* @file: file being read
* @page: structure to page
*
*/
static int v9fs_vfs_readpage(struct file *filp, struct page *page)
static int v9fs_vfs_readpage(struct file *file, struct page *page)
{
return v9fs_fid_readpage(filp->private_data, page);
return netfs_readpage(file, page, &v9fs_req_ops, NULL);
}
/**
* v9fs_vfs_readpages - read a set of pages from 9P
*
* @filp: file being read
* @mapping: the address space
* @pages: list of pages to read
* @nr_pages: count of pages to read
*
* v9fs_vfs_readahead - read a set of pages from 9P
* @ractl: The readahead parameters
*/
static int v9fs_vfs_readpages(struct file *filp, struct address_space *mapping,
struct list_head *pages, unsigned nr_pages)
static void v9fs_vfs_readahead(struct readahead_control *ractl)
{
int ret = 0;
struct inode *inode;
inode = mapping->host;
p9_debug(P9_DEBUG_VFS, "inode: %p file: %p\n", inode, filp);
ret = v9fs_readpages_from_fscache(inode, mapping, pages, &nr_pages);
if (ret == 0)
return ret;
ret = read_cache_pages(mapping, pages, v9fs_fid_readpage,
filp->private_data);
p9_debug(P9_DEBUG_VFS, " = %d\n", ret);
return ret;
netfs_readahead(ractl, &v9fs_req_ops, NULL);
}
/**
@ -125,7 +134,14 @@ static int v9fs_release_page(struct page *page, gfp_t gfp)
{
if (PagePrivate(page))
return 0;
return v9fs_fscache_release_page(page, gfp);
#ifdef CONFIG_9P_FSCACHE
if (PageFsCache(page)) {
if (!(gfp & __GFP_DIRECT_RECLAIM) || !(gfp & __GFP_FS))
return 0;
wait_on_page_fscache(page);
}
#endif
return 1;
}
/**
@ -138,21 +154,16 @@ static int v9fs_release_page(struct page *page, gfp_t gfp)
static void v9fs_invalidate_page(struct page *page, unsigned int offset,
unsigned int length)
{
/*
* If called with zero offset, we should release
* the private state assocated with the page
*/
if (offset == 0 && length == PAGE_SIZE)
v9fs_fscache_invalidate_page(page);
wait_on_page_fscache(page);
}
static int v9fs_vfs_writepage_locked(struct page *page)
{
struct inode *inode = page->mapping->host;
struct v9fs_inode *v9inode = V9FS_I(inode);
loff_t start = page_offset(page);
loff_t size = i_size_read(inode);
struct iov_iter from;
struct bio_vec bvec;
int err, len;
if (page->index == size >> PAGE_SHIFT)
@ -160,17 +171,14 @@ static int v9fs_vfs_writepage_locked(struct page *page)
else
len = PAGE_SIZE;
bvec.bv_page = page;
bvec.bv_offset = 0;
bvec.bv_len = len;
iov_iter_bvec(&from, WRITE, &bvec, 1, len);
iov_iter_xarray(&from, WRITE, &page->mapping->i_pages, start, len);
/* We should have writeback_fid always set */
BUG_ON(!v9inode->writeback_fid);
set_page_writeback(page);
p9_client_write(v9inode->writeback_fid, page_offset(page), &from, &err);
p9_client_write(v9inode->writeback_fid, start, &from, &err);
end_page_writeback(page);
return err;
@ -208,14 +216,13 @@ static int v9fs_vfs_writepage(struct page *page, struct writeback_control *wbc)
static int v9fs_launder_page(struct page *page)
{
int retval;
struct inode *inode = page->mapping->host;
v9fs_fscache_wait_on_page_write(inode, page);
if (clear_page_dirty_for_io(page)) {
retval = v9fs_vfs_writepage_locked(page);
if (retval)
return retval;
}
wait_on_page_fscache(page);
return 0;
}
@ -260,35 +267,24 @@ static int v9fs_write_begin(struct file *filp, struct address_space *mapping,
loff_t pos, unsigned len, unsigned flags,
struct page **pagep, void **fsdata)
{
int retval = 0;
int retval;
struct page *page;
struct v9fs_inode *v9inode;
pgoff_t index = pos >> PAGE_SHIFT;
struct inode *inode = mapping->host;
struct v9fs_inode *v9inode = V9FS_I(mapping->host);
p9_debug(P9_DEBUG_VFS, "filp %p, mapping %p\n", filp, mapping);
v9inode = V9FS_I(inode);
start:
page = grab_cache_page_write_begin(mapping, index, flags);
if (!page) {
retval = -ENOMEM;
goto out;
}
BUG_ON(!v9inode->writeback_fid);
if (PageUptodate(page))
goto out;
if (len == PAGE_SIZE)
goto out;
/* 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(filp, mapping, pos, len, flags, &page, fsdata,
&v9fs_req_ops, NULL);
if (retval < 0)
return retval;
retval = v9fs_fid_readpage(v9inode->writeback_fid, page);
put_page(page);
if (!retval)
goto start;
out:
*pagep = page;
*pagep = find_subpage(page, pos / PAGE_SIZE);
return retval;
}
@ -305,10 +301,11 @@ static int v9fs_write_end(struct file *filp, struct address_space *mapping,
if (unlikely(copied < len)) {
copied = 0;
goto out;
} else if (len == PAGE_SIZE) {
SetPageUptodate(page);
}
SetPageUptodate(page);
}
/*
* No need to use i_size_read() here, the i_size
* cannot change under us because we hold the i_mutex.
@ -328,7 +325,7 @@ static int v9fs_write_end(struct file *filp, struct address_space *mapping,
const struct address_space_operations v9fs_addr_operations = {
.readpage = v9fs_vfs_readpage,
.readpages = v9fs_vfs_readpages,
.readahead = v9fs_vfs_readahead,
.set_page_dirty = __set_page_dirty_nobuffers,
.writepage = v9fs_vfs_writepage,
.write_begin = v9fs_write_begin,

17
fs/9p/vfs_file.c
View file

@ -537,14 +537,23 @@ v9fs_vm_page_mkwrite(struct vm_fault *vmf)
p9_debug(P9_DEBUG_VFS, "page %p fid %lx\n",
page, (unsigned long)filp->private_data);
v9inode = V9FS_I(inode);
/* Wait for the page to be written to the cache before we allow it to
* be modified. We then assume the entire page will need writing back.
*/
#ifdef CONFIG_9P_FSCACHE
if (PageFsCache(page) &&
wait_on_page_fscache_killable(page) < 0)
return VM_FAULT_RETRY;
#endif
/* Update file times before taking page lock */
file_update_time(filp);
v9inode = V9FS_I(inode);
/* make sure the cache has finished storing the page */
v9fs_fscache_wait_on_page_write(inode, page);
BUG_ON(!v9inode->writeback_fid);
lock_page(page);
if (lock_page_killable(page) < 0)
return VM_FAULT_RETRY;
if (page->mapping != inode->i_mapping)
goto out_unlock;
wait_for_stable_page(page);