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