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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 (dhowells@redhat.com)
*
* 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);
/*
* 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 list_head subrequests; /* Requests to fetch I/O from disk or net */
void *netfs_priv; /* Private data for the netfs */
unsigned int debug_id;
atomic_t nr_rd_ops; /* Number of read 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 {
void (*init_rreq)(struct netfs_read_request *rreq, struct file *file);
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);
void (*done)(struct netfs_read_request *rreq);
void (*cleanup)(struct address_space *mapping, void *netfs_priv);
};
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 void netfs_subreq_terminated(struct netfs_read_subrequest *, ssize_t, bool);
#endif /* _LINUX_NETFS_H */
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