/* 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>
#include <linux/uio.h>
#include <linux/rolling_buffer.h>

enum netfs_sreq_ref_trace;
typedef struct mempool mempool_t;
struct folio_queue;

/**
 * folio_start_private_2 - Start an fscache write on a folio.  [DEPRECATED]
 * @folio: The folio.
 *
 * Call this function before writing a folio to a local cache.  Starting a
 * second write before the first one finishes is not allowed.
 *
 * Note that this should no longer be used.
 */
static inline void folio_start_private_2(struct folio *folio)
{
        VM_BUG_ON_FOLIO(folio_test_private_2(folio), folio);
        folio_get(folio);
        folio_set_private_2(folio);
}

enum netfs_io_source {
        NETFS_SOURCE_UNKNOWN,
        NETFS_FILL_WITH_ZEROES,
        NETFS_DOWNLOAD_FROM_SERVER,
        NETFS_READ_FROM_CACHE,
        NETFS_INVALID_READ,
        NETFS_UPLOAD_TO_SERVER,
        NETFS_WRITE_TO_CACHE,
} __mode(byte);

typedef void (*netfs_io_terminated_t)(void *priv, ssize_t transferred_or_error);

/*
 * Per-inode context.  This wraps the VFS inode.
 */
struct netfs_inode {
        struct inode            inode;          /* The VFS inode */
        const struct netfs_request_ops *ops;
#if IS_ENABLED(CONFIG_FSCACHE)
        struct fscache_cookie   *cache;
#endif
        struct mutex            wb_lock;        /* Writeback serialisation */
        loff_t                  remote_i_size;  /* Size of the remote file */
        loff_t                  zero_point;     /* Size after which we assume there's no data
                                                 * on the server */
        atomic_t                io_count;       /* Number of outstanding reqs */
        unsigned long           flags;
#define NETFS_ICTX_ODIRECT      0               /* The file has DIO in progress */
#define NETFS_ICTX_UNBUFFERED   1               /* I/O should not use the pagecache */
#define NETFS_ICTX_MODIFIED_ATTR 3              /* Indicate change in mtime/ctime */
#define NETFS_ICTX_SINGLE_NO_UPLOAD 4           /* Monolithic payload, cache but no upload */
};

/*
 * A netfs group - for instance a ceph snap.  This is marked on dirty pages and
 * pages marked with a group must be flushed before they can be written under
 * the domain of another group.
 */
struct netfs_group {
        refcount_t              ref;
        void (*free)(struct netfs_group *netfs_group);
};

/*
 * Information about a dirty page (attached only if necessary).
 * folio->private
 */
struct netfs_folio {
        struct netfs_group      *netfs_group;   /* Filesystem's grouping marker (or NULL). */
        unsigned int            dirty_offset;   /* Write-streaming dirty data offset */
        unsigned int            dirty_len;      /* Write-streaming dirty data length */
};
#define NETFS_FOLIO_INFO        0x1UL   /* OR'd with folio->private. */
#define NETFS_FOLIO_COPY_TO_CACHE ((struct netfs_group *)0x356UL) /* Write to the cache only */

static inline bool netfs_is_folio_info(const void *priv)
{
        return (unsigned long)priv & NETFS_FOLIO_INFO;
}

static inline struct netfs_folio *__netfs_folio_info(const void *priv)
{
        if (netfs_is_folio_info(priv))
                return (struct netfs_folio *)((unsigned long)priv & ~NETFS_FOLIO_INFO);
        return NULL;
}

static inline struct netfs_folio *netfs_folio_info(struct folio *folio)
{
        return __netfs_folio_info(folio_get_private(folio));
}

static inline struct netfs_group *netfs_folio_group(struct folio *folio)
{
        struct netfs_folio *finfo;
        void *priv = folio_get_private(folio);

        finfo = netfs_folio_info(folio);
        if (finfo)
                return finfo->netfs_group;
        return priv;
}

/*
 * Stream of I/O subrequests going to a particular destination, such as the
 * server or the local cache.  This is mainly intended for writing where we may
 * have to write to multiple destinations concurrently.
 */
struct netfs_io_stream {
        /* Submission tracking */
        struct netfs_io_subrequest *construct;  /* Op being constructed */
        size_t                  sreq_max_len;   /* Maximum size of a subrequest */
        unsigned int            sreq_max_segs;  /* 0 or max number of segments in an iterator */
        unsigned int            submit_off;     /* Folio offset we're submitting from */
        unsigned int            submit_len;     /* Amount of data left to submit */
        unsigned int            submit_extendable_to; /* Amount I/O can be rounded up to */
        void (*prepare_write)(struct netfs_io_subrequest *subreq);
        void (*issue_write)(struct netfs_io_subrequest *subreq);
        /* Collection tracking */
        struct list_head        subrequests;    /* Contributory I/O operations */
        unsigned long long      collected_to;   /* Position we've collected results to */
        size_t                  transferred;    /* The amount transferred from this stream */
        unsigned short          error;          /* Aggregate error for the stream */
        enum netfs_io_source    source;         /* Where to read from/write to */
        unsigned char           stream_nr;      /* Index of stream in parent table */
        bool                    avail;          /* T if stream is available */
        bool                    active;         /* T if stream is active */
        bool                    need_retry;     /* T if this stream needs retrying */
        bool                    failed;         /* T if this stream failed */
        bool                    transferred_valid; /* T is ->transferred is valid */
};

/*
 * Resources required to do operations on a cache.
 */
struct netfs_cache_resources {
        const struct netfs_cache_ops    *ops;
        void                            *cache_priv;
        void                            *cache_priv2;
        unsigned int                    debug_id;       /* Cookie debug ID */
        unsigned int                    inval_counter;  /* object->inval_counter at begin_op */
};

/*
 * Descriptor for a single component subrequest.  Each operation represents an
 * individual read/write from/to a server, a cache, a journal, etc..
 *
 * The buffer iterator is persistent for the life of the subrequest struct and
 * the pages it points to can be relied on to exist for the duration.
 */
struct netfs_io_subrequest {
        struct netfs_io_request *rreq;          /* Supervising I/O request */
        struct work_struct      work;
        struct list_head        rreq_link;      /* Link in rreq->subrequests */
        struct iov_iter         io_iter;        /* Iterator for this subrequest */
        unsigned long long      start;          /* Where to start the I/O */
        size_t                  len;            /* Size of the I/O */
        size_t                  transferred;    /* Amount of data transferred */
        refcount_t              ref;
        short                   error;          /* 0 or error that occurred */
        unsigned short          debug_index;    /* Index in list (for debugging output) */
        unsigned int            nr_segs;        /* Number of segs in io_iter */
        u8                      retry_count;    /* The number of retries (0 on initial pass) */
        enum netfs_io_source    source;         /* Where to read from/write to */
        unsigned char           stream_nr;      /* I/O stream this belongs to */
        unsigned long           flags;
#define NETFS_SREQ_COPY_TO_CACHE        0       /* Set if should copy the data to the cache */
#define NETFS_SREQ_CLEAR_TAIL           1       /* Set if the rest of the read should be cleared */
#define NETFS_SREQ_MADE_PROGRESS        4       /* Set if we transferred at least some data */
#define NETFS_SREQ_ONDEMAND             5       /* Set if it's from on-demand read mode */
#define NETFS_SREQ_BOUNDARY             6       /* Set if ends on hard boundary (eg. ceph object) */
#define NETFS_SREQ_HIT_EOF              7       /* Set if short due to EOF */
#define NETFS_SREQ_IN_PROGRESS          8       /* Unlocked when the subrequest completes */
#define NETFS_SREQ_NEED_RETRY           9       /* Set if the filesystem requests a retry */
#define NETFS_SREQ_FAILED               10      /* Set if the subreq failed unretryably */
};

enum netfs_io_origin {
        NETFS_READAHEAD,                /* This read was triggered by readahead */
        NETFS_READPAGE,                 /* This read is a synchronous read */
        NETFS_READ_GAPS,                /* This read is a synchronous read to fill gaps */
        NETFS_READ_SINGLE,              /* This read should be treated as a single object */
        NETFS_READ_FOR_WRITE,           /* This read is to prepare a write */
        NETFS_UNBUFFERED_READ,          /* This is an unbuffered read */
        NETFS_DIO_READ,                 /* This is a direct I/O read */
        NETFS_WRITEBACK,                /* This write was triggered by writepages */
        NETFS_WRITEBACK_SINGLE,         /* This monolithic write was triggered by writepages */
        NETFS_WRITETHROUGH,             /* This write was made by netfs_perform_write() */
        NETFS_UNBUFFERED_WRITE,         /* This is an unbuffered write */
        NETFS_DIO_WRITE,                /* This is a direct I/O write */
        NETFS_PGPRIV2_COPY_TO_CACHE,    /* [DEPRECATED] This is writing read data to the cache */
        nr__netfs_io_origin
} __mode(byte);

/*
 * Descriptor for an I/O helper request.  This is used to make multiple I/O
 * operations to a variety of data stores and then stitch the result together.
 */
struct netfs_io_request {
        union {
                struct work_struct cleanup_work; /* Deferred cleanup work */
                struct rcu_head rcu;
        };
        struct work_struct      work;           /* Result collector work */
        struct inode            *inode;         /* The file being accessed */
        struct address_space    *mapping;       /* The mapping being accessed */
        struct kiocb            *iocb;          /* AIO completion vector */
        struct netfs_cache_resources cache_resources;
        struct netfs_io_request *copy_to_cache; /* Request to write just-read data to the cache */
#ifdef CONFIG_PROC_FS
        struct list_head        proc_link;      /* Link in netfs_iorequests */
#endif
        struct netfs_io_stream  io_streams[2];  /* Streams of parallel I/O operations */
#define NR_IO_STREAMS 2 //wreq->nr_io_streams
        struct netfs_group      *group;         /* Writeback group being written back */
        struct rolling_buffer   buffer;         /* Unencrypted buffer */
#define NETFS_ROLLBUF_PUT_MARK          ROLLBUF_MARK_1
#define NETFS_ROLLBUF_PAGECACHE_MARK    ROLLBUF_MARK_2
        wait_queue_head_t       waitq;          /* Processor waiter */
        void                    *netfs_priv;    /* Private data for the netfs */
        void                    *netfs_priv2;   /* Private data for the netfs */
        struct bio_vec          *direct_bv;     /* DIO buffer list (when handling iovec-iter) */
        unsigned long long      submitted;      /* Amount submitted for I/O so far */
        unsigned long long      len;            /* Length of the request */
        size_t                  transferred;    /* Amount to be indicated as transferred */
        long                    error;          /* 0 or error that occurred */
        unsigned long long      i_size;         /* Size of the file */
        unsigned long long      start;          /* Start position */
        atomic64_t              issued_to;      /* Write issuer folio cursor */
        unsigned long long      collected_to;   /* Point we've collected to */
        unsigned long long      cleaned_to;     /* Position we've cleaned folios to */
        unsigned long long      abandon_to;     /* Position to abandon folios to */
        pgoff_t                 no_unlock_folio; /* Don't unlock this folio after read */
        unsigned int            direct_bv_count; /* Number of elements in direct_bv[] */
        unsigned int            debug_id;
        unsigned int            rsize;          /* Maximum read size (0 for none) */
        unsigned int            wsize;          /* Maximum write size (0 for none) */
        atomic_t                subreq_counter; /* Next subreq->debug_index */
        unsigned int            nr_group_rel;   /* Number of refs to release on ->group */
        spinlock_t              lock;           /* Lock for queuing subreqs */
        unsigned char           front_folio_order; /* Order (size) of front folio */
        enum netfs_io_origin    origin;         /* Origin of the request */
        bool                    direct_bv_unpin; /* T if direct_bv[] must be unpinned */
        refcount_t              ref;
        unsigned long           flags;
#define NETFS_RREQ_IN_PROGRESS          0       /* Unlocked when the request completes (has ref) */
#define NETFS_RREQ_ALL_QUEUED           1       /* All subreqs are now queued */
#define NETFS_RREQ_PAUSE                2       /* Pause subrequest generation */
#define NETFS_RREQ_FAILED               3       /* The request failed */
#define NETFS_RREQ_RETRYING             4       /* Set if we're in the retry path */
#define NETFS_RREQ_SHORT_TRANSFER       5       /* Set if we have a short transfer */
#define NETFS_RREQ_OFFLOAD_COLLECTION   8       /* Offload collection to workqueue */
#define NETFS_RREQ_NO_UNLOCK_FOLIO      9       /* Don't unlock no_unlock_folio on completion */
#define NETFS_RREQ_FOLIO_COPY_TO_CACHE  10      /* Copy current folio to cache from read */
#define NETFS_RREQ_UPLOAD_TO_SERVER     11      /* Need to write to the server */
#define NETFS_RREQ_USE_IO_ITER          12      /* Use ->io_iter rather than ->i_pages */
#define NETFS_RREQ_USE_PGPRIV2          31      /* [DEPRECATED] Use PG_private_2 to mark
                                                 * write to cache on read */
        const struct netfs_request_ops *netfs_ops;
};

/*
 * Operations the network filesystem can/must provide to the helpers.
 */
struct netfs_request_ops {
        mempool_t *request_pool;
        mempool_t *subrequest_pool;
        int (*init_request)(struct netfs_io_request *rreq, struct file *file);
        void (*free_request)(struct netfs_io_request *rreq);
        void (*free_subrequest)(struct netfs_io_subrequest *rreq);

        /* Read request handling */
        void (*expand_readahead)(struct netfs_io_request *rreq);
        int (*prepare_read)(struct netfs_io_subrequest *subreq);
        void (*issue_read)(struct netfs_io_subrequest *subreq);
        bool (*is_still_valid)(struct netfs_io_request *rreq);
        int (*check_write_begin)(struct file *file, loff_t pos, unsigned len,
                                 struct folio **foliop, void **_fsdata);
        void (*done)(struct netfs_io_request *rreq);

        /* Modification handling */
        void (*update_i_size)(struct inode *inode, loff_t i_size);
        void (*post_modify)(struct inode *inode);

        /* Write request handling */
        void (*begin_writeback)(struct netfs_io_request *wreq);
        void (*prepare_write)(struct netfs_io_subrequest *subreq);
        void (*issue_write)(struct netfs_io_subrequest *subreq);
        void (*retry_request)(struct netfs_io_request *wreq, struct netfs_io_stream *stream);
        void (*invalidate_cache)(struct netfs_io_request *wreq);
};

/*
 * How to handle reading from a hole.
 */
enum netfs_read_from_hole {
        NETFS_READ_HOLE_IGNORE,
        NETFS_READ_HOLE_FAIL,
};

/*
 * Table of operations for access to a cache.
 */
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,
                    enum netfs_read_from_hole read_hole,
                    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);

        /* Write data to the cache from a netfs subrequest. */
        void (*issue_write)(struct netfs_io_subrequest *subreq);

        /* Expand readahead request */
        void (*expand_readahead)(struct netfs_cache_resources *cres,
                                 unsigned long long *_start,
                                 unsigned long long *_len,
                                 unsigned long long i_size);

        /* Prepare a read operation, shortening it to a cached/uncached
         * boundary as appropriate.
         */
        enum netfs_io_source (*prepare_read)(struct netfs_io_subrequest *subreq,
                                             unsigned long long i_size);

        /* Prepare a write subrequest, working out if we're allowed to do it
         * and finding out the maximum amount of data to gather before
         * attempting to submit.  If we're not permitted to do it, the
         * subrequest should be marked failed.
         */
        void (*prepare_write_subreq)(struct netfs_io_subrequest *subreq);

        /* 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, size_t upper_len,
                             loff_t i_size, bool no_space_allocated_yet);

        /* Prepare an on-demand read operation, shortening it to a cached/uncached
         * boundary as appropriate.
         */
        enum netfs_io_source (*prepare_ondemand_read)(struct netfs_cache_resources *cres,
                                                      loff_t start, size_t *_len,
                                                      loff_t i_size,
                                                      unsigned long *_flags, ino_t ino);

        /* Query the occupancy of the cache in a region, returning where the
         * next chunk of data starts and how long it is.
         */
        int (*query_occupancy)(struct netfs_cache_resources *cres,
                               loff_t start, size_t len, size_t granularity,
                               loff_t *_data_start, size_t *_data_len);
};

/* High-level read API. */
ssize_t netfs_unbuffered_read_iter_locked(struct kiocb *iocb, struct iov_iter *iter);
ssize_t netfs_unbuffered_read_iter(struct kiocb *iocb, struct iov_iter *iter);
ssize_t netfs_buffered_read_iter(struct kiocb *iocb, struct iov_iter *iter);
ssize_t netfs_file_read_iter(struct kiocb *iocb, struct iov_iter *iter);

/* High-level write API */
ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
                            struct netfs_group *netfs_group);
ssize_t netfs_buffered_write_iter_locked(struct kiocb *iocb, struct iov_iter *from,
                                         struct netfs_group *netfs_group);
ssize_t netfs_unbuffered_write_iter(struct kiocb *iocb, struct iov_iter *from);
ssize_t netfs_unbuffered_write_iter_locked(struct kiocb *iocb, struct iov_iter *iter,
                                           struct netfs_group *netfs_group);
ssize_t netfs_file_write_iter(struct kiocb *iocb, struct iov_iter *from);

/* Single, monolithic object read/write API. */
void netfs_single_mark_inode_dirty(struct inode *inode);
ssize_t netfs_read_single(struct inode *inode, struct file *file, struct iov_iter *iter);
int netfs_writeback_single(struct address_space *mapping,
                           struct writeback_control *wbc,
                           struct iov_iter *iter);

/* Address operations API */
struct readahead_control;
void netfs_readahead(struct readahead_control *);
int netfs_read_folio(struct file *, struct folio *);
int netfs_write_begin(struct netfs_inode *, struct file *,
                      struct address_space *, loff_t pos, unsigned int len,
                      struct folio **, void **fsdata);
int netfs_writepages(struct address_space *mapping,
                     struct writeback_control *wbc);
bool netfs_dirty_folio(struct address_space *mapping, struct folio *folio);
int netfs_unpin_writeback(struct inode *inode, struct writeback_control *wbc);
void netfs_clear_inode_writeback(struct inode *inode, const void *aux);
void netfs_invalidate_folio(struct folio *folio, size_t offset, size_t length);
bool netfs_release_folio(struct folio *folio, gfp_t gfp);

/* VMA operations API. */
vm_fault_t netfs_page_mkwrite(struct vm_fault *vmf, struct netfs_group *netfs_group);

/* (Sub)request management API. */
void netfs_read_subreq_progress(struct netfs_io_subrequest *subreq);
void netfs_read_subreq_terminated(struct netfs_io_subrequest *subreq);
void netfs_get_subrequest(struct netfs_io_subrequest *subreq,
                          enum netfs_sreq_ref_trace what);
void netfs_put_subrequest(struct netfs_io_subrequest *subreq,
                          enum netfs_sreq_ref_trace what);
ssize_t netfs_extract_user_iter(struct iov_iter *orig, size_t orig_len,
                                struct iov_iter *new,
                                iov_iter_extraction_t extraction_flags);
size_t netfs_limit_iter(const struct iov_iter *iter, size_t start_offset,
                        size_t max_size, size_t max_segs);
void netfs_prepare_write_failed(struct netfs_io_subrequest *subreq);
void netfs_write_subrequest_terminated(void *_op, ssize_t transferred_or_error);

int netfs_start_io_read(struct inode *inode);
void netfs_end_io_read(struct inode *inode);
int netfs_start_io_write(struct inode *inode);
void netfs_end_io_write(struct inode *inode);
int netfs_start_io_direct(struct inode *inode);
void netfs_end_io_direct(struct inode *inode);

/* Miscellaneous APIs. */
struct folio_queue *netfs_folioq_alloc(unsigned int rreq_id, gfp_t gfp,
                                       unsigned int trace /*enum netfs_folioq_trace*/);
void netfs_folioq_free(struct folio_queue *folioq,
                       unsigned int trace /*enum netfs_trace_folioq*/);

/* Buffer wrangling helpers API. */
int netfs_alloc_folioq_buffer(struct address_space *mapping,
                              struct folio_queue **_buffer,
                              size_t *_cur_size, ssize_t size, gfp_t gfp);
void netfs_free_folioq_buffer(struct folio_queue *fq);

/**
 * netfs_inode - Get the netfs inode context from the inode
 * @inode: The inode to query
 *
 * Get the netfs lib inode context from the network filesystem's inode.  The
 * context struct is expected to directly follow on from the VFS inode struct.
 */
static inline struct netfs_inode *netfs_inode(struct inode *inode)
{
        return container_of(inode, struct netfs_inode, inode);
}

/**
 * netfs_inode_init - Initialise a netfslib inode context
 * @ctx: The netfs inode to initialise
 * @ops: The netfs's operations list
 * @use_zero_point: True to use the zero_point read optimisation
 *
 * Initialise the netfs library context struct.  This is expected to follow on
 * directly from the VFS inode struct.
 */
static inline void netfs_inode_init(struct netfs_inode *ctx,
                                    const struct netfs_request_ops *ops,
                                    bool use_zero_point)
{
        ctx->ops = ops;
        ctx->remote_i_size = i_size_read(&ctx->inode);
        ctx->zero_point = LLONG_MAX;
        ctx->flags = 0;
        atomic_set(&ctx->io_count, 0);
#if IS_ENABLED(CONFIG_FSCACHE)
        ctx->cache = NULL;
#endif
        mutex_init(&ctx->wb_lock);
        /* ->releasepage() drives zero_point */
        if (use_zero_point) {
                ctx->zero_point = ctx->remote_i_size;
                mapping_set_release_always(ctx->inode.i_mapping);
        }
}

/**
 * netfs_resize_file - Note that a file got resized
 * @ctx: The netfs inode being resized
 * @new_i_size: The new file size
 * @changed_on_server: The change was applied to the server
 *
 * Inform the netfs lib that a file got resized so that it can adjust its state.
 */
static inline void netfs_resize_file(struct netfs_inode *ctx, loff_t new_i_size,
                                     bool changed_on_server)
{
        if (changed_on_server)
                ctx->remote_i_size = new_i_size;
        if (new_i_size < ctx->zero_point)
                ctx->zero_point = new_i_size;
}

/**
 * netfs_i_cookie - Get the cache cookie from the inode
 * @ctx: The netfs inode to query
 *
 * Get the caching cookie (if enabled) from the network filesystem's inode.
 */
static inline struct fscache_cookie *netfs_i_cookie(struct netfs_inode *ctx)
{
#if IS_ENABLED(CONFIG_FSCACHE)
        return ctx->cache;
#else
        return NULL;
#endif
}

/**
 * netfs_wait_for_outstanding_io - Wait for outstanding I/O to complete
 * @inode: The netfs inode to wait on
 *
 * Wait for outstanding I/O requests of any type to complete.  This is intended
 * to be called from inode eviction routines.  This makes sure that any
 * resources held by those requests are cleaned up before we let the inode get
 * cleaned up.
 */
static inline void netfs_wait_for_outstanding_io(struct inode *inode)
{
        struct netfs_inode *ictx = netfs_inode(inode);

        wait_var_event(&ictx->io_count, atomic_read(&ictx->io_count) == 0);
}

#endif /* _LINUX_NETFS_H */