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/* SPDX-License-Identifier: GPL-2.0-or-later */
/* Network filesystem support services.
*
* Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
* Written by David Howells ([email protected])
*
* See:
*
* Documentation/filesystems/netfs_library.rst
*
* for a description of the network filesystem interface declared here.
*/
#ifndef _LINUX_NETFS_H
#define _LINUX_NETFS_H
#include <linux/workqueue.h>
#include <linux/fs.h>
#include <linux/pagemap.h>
/*
* Overload PG_private_2 to give us PG_fscache - this is used to indicate that
* a page is currently backed by a local disk cache
*/
#define PageFsCache(page) PagePrivate2((page))
#define SetPageFsCache(page) SetPagePrivate2((page))
#define ClearPageFsCache(page) ClearPagePrivate2((page))
#define TestSetPageFsCache(page) TestSetPagePrivate2((page))
#define TestClearPageFsCache(page) TestClearPagePrivate2((page))
/**
* set_page_fscache - Set PG_fscache on a page and take a ref
* @page: The page.
*
* Set the PG_fscache (PG_private_2) flag on a page and take the reference
* needed for the VM to handle its lifetime correctly. This sets the flag and
* takes the reference unconditionally, so care must be taken not to set the
* flag again if it's already set.
*/
static inline void set_page_fscache(struct page *page)
{
set_page_private_2(page);
}
/**
* end_page_fscache - Clear PG_fscache and release any waiters
* @page: The page
*
* Clear the PG_fscache (PG_private_2) bit on a page and wake up any sleepers
* waiting for this. The page ref held for PG_private_2 being set is released.
*
* This is, for example, used when a netfs page is being written to a local
* disk cache, thereby allowing writes to the cache for the same page to be
* serialised.
*/
static inline void end_page_fscache(struct page *page)
{
end_page_private_2(page);
}
/**
* wait_on_page_fscache - Wait for PG_fscache to be cleared on a page
* @page: The page to wait on
*
* Wait for PG_fscache (aka PG_private_2) to be cleared on a page.
*/
static inline void wait_on_page_fscache(struct page *page)
{
wait_on_page_private_2(page);
}
/**
* wait_on_page_fscache_killable - Wait for PG_fscache to be cleared on a page
* @page: The page to wait on
*
* Wait for PG_fscache (aka PG_private_2) to be cleared on a page or until a
* fatal signal is received by the calling task.
*
* Return:
* - 0 if successful.
* - -EINTR if a fatal signal was encountered.
*/
static inline int wait_on_page_fscache_killable(struct page *page)
{
return wait_on_page_private_2_killable(page);
}
enum netfs_read_source {
NETFS_FILL_WITH_ZEROES,
NETFS_DOWNLOAD_FROM_SERVER,
NETFS_READ_FROM_CACHE,
NETFS_INVALID_READ,
} __mode(byte);
typedef void (*netfs_io_terminated_t)(void *priv, ssize_t transferred_or_error,
bool was_async);
/*
* Resources required to do operations on a cache.
*/
struct netfs_cache_resources {
const struct netfs_cache_ops *ops;
void *cache_priv;
void *cache_priv2;
};
/*
* Descriptor for a single component subrequest.
*/
struct netfs_read_subrequest {
struct netfs_read_request *rreq; /* Supervising read request */
struct list_head rreq_link; /* Link in rreq->subrequests */
loff_t start; /* Where to start the I/O */
size_t len; /* Size of the I/O */
size_t transferred; /* Amount of data transferred */
refcount_t usage;
short error; /* 0 or error that occurred */
unsigned short debug_index; /* Index in list (for debugging output) */
enum netfs_read_source source; /* Where to read from */
unsigned long flags;
#define NETFS_SREQ_WRITE_TO_CACHE 0 /* Set if should write to cache */
#define NETFS_SREQ_CLEAR_TAIL 1 /* Set if the rest of the read should be cleared */
#define NETFS_SREQ_SHORT_READ 2 /* Set if there was a short read from the cache */
#define NETFS_SREQ_SEEK_DATA_READ 3 /* Set if ->read() should SEEK_DATA first */
#define NETFS_SREQ_NO_PROGRESS 4 /* Set if we didn't manage to read any data */
};
/*
* Descriptor for a read helper request. This is used to make multiple I/O
* requests on a variety of sources and then stitch the result together.
*/
struct netfs_read_request {
struct work_struct work;
struct inode *inode; /* The file being accessed */
struct address_space *mapping; /* The mapping being accessed */
struct netfs_cache_resources cache_resources;
struct list_head subrequests; /* Requests to fetch I/O from disk or net */
void *netfs_priv; /* Private data for the netfs */
unsigned int debug_id;
unsigned int cookie_debug_id;
atomic_t nr_rd_ops; /* Number of read ops in progress */
atomic_t nr_wr_ops; /* Number of write ops in progress */
size_t submitted; /* Amount submitted for I/O so far */
size_t len; /* Length of the request */
short error; /* 0 or error that occurred */
loff_t i_size; /* Size of the file */
loff_t start; /* Start position */
pgoff_t no_unlock_page; /* Don't unlock this page after read */
refcount_t usage;
unsigned long flags;
#define NETFS_RREQ_INCOMPLETE_IO 0 /* Some ioreqs terminated short or with error */
#define NETFS_RREQ_WRITE_TO_CACHE 1 /* Need to write to the cache */
#define NETFS_RREQ_NO_UNLOCK_PAGE 2 /* Don't unlock no_unlock_page on completion */
#define NETFS_RREQ_DONT_UNLOCK_PAGES 3 /* Don't unlock the pages on completion */
#define NETFS_RREQ_FAILED 4 /* The request failed */
#define NETFS_RREQ_IN_PROGRESS 5 /* Unlocked when the request completes */
const struct netfs_read_request_ops *netfs_ops;
};
/*
* Operations the network filesystem can/must provide to the helpers.
*/
struct netfs_read_request_ops {
bool (*is_cache_enabled)(struct inode *inode);
void (*init_rreq)(struct netfs_read_request *rreq, struct file *file);
int (*begin_cache_operation)(struct netfs_read_request *rreq);
void (*expand_readahead)(struct netfs_read_request *rreq);
bool (*clamp_length)(struct netfs_read_subrequest *subreq);
void (*issue_op)(struct netfs_read_subrequest *subreq);
bool (*is_still_valid)(struct netfs_read_request *rreq);
int (*check_write_begin)(struct file *file, loff_t pos, unsigned len,
struct page *page, void **_fsdata);
void (*done)(struct netfs_read_request *rreq);
void (*cleanup)(struct address_space *mapping, void *netfs_priv);
};
/*
* Table of operations for access to a cache. This is obtained by
* rreq->ops->begin_cache_operation().
*/
struct netfs_cache_ops {
/* End an operation */
void (*end_operation)(struct netfs_cache_resources *cres);
/* Read data from the cache */
int (*read)(struct netfs_cache_resources *cres,
loff_t start_pos,
struct iov_iter *iter,
bool seek_data,
netfs_io_terminated_t term_func,
void *term_func_priv);
/* Write data to the cache */
int (*write)(struct netfs_cache_resources *cres,
loff_t start_pos,
struct iov_iter *iter,
netfs_io_terminated_t term_func,
void *term_func_priv);
/* Expand readahead request */
void (*expand_readahead)(struct netfs_cache_resources *cres,
loff_t *_start, size_t *_len, loff_t i_size);
/* Prepare a read operation, shortening it to a cached/uncached
* boundary as appropriate.
*/
enum netfs_read_source (*prepare_read)(struct netfs_read_subrequest *subreq,
loff_t i_size);
/* Prepare a write operation, working out what part of the write we can
* actually do.
*/
int (*prepare_write)(struct netfs_cache_resources *cres,
loff_t *_start, size_t *_len, loff_t i_size);
};
struct readahead_control;
extern void netfs_readahead(struct readahead_control *,
const struct netfs_read_request_ops *,
void *);
extern int netfs_readpage(struct file *,
struct page *,
const struct netfs_read_request_ops *,
void *);
extern int netfs_write_begin(struct file *, struct address_space *,
loff_t, unsigned int, unsigned int, struct page **,
void **,
const struct netfs_read_request_ops *,
void *);
extern void netfs_subreq_terminated(struct netfs_read_subrequest *, ssize_t, bool);
extern void netfs_stats_show(struct seq_file *);
#endif /* _LINUX_NETFS_H */
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