Import 2.3.6pre2

[davej-history.git] / fs / nfs / write.c

/*
 * linux/fs/nfs/write.c
 *
 * Writing file data over NFS.
 *
 * We do it like this: When a (user) process wishes to write data to an
 * NFS file, a write request is allocated that contains the RPC task data
 * plus some info on the page to be written, and added to the inode's
 * write chain. If the process writes past the end of the page, an async
 * RPC call to write the page is scheduled immediately; otherwise, the call
 * is delayed for a few seconds.
 *
 * Just like readahead, no async I/O is performed if wsize < PAGE_SIZE.
 *
 * Write requests are kept on the inode's writeback list. Each entry in
 * that list references the page (portion) to be written. When the
 * cache timeout has expired, the RPC task is woken up, and tries to
 * lock the page. As soon as it manages to do so, the request is moved
 * from the writeback list to the writelock list.
 *
 * Note: we must make sure never to confuse the inode passed in the
 * write_page request with the one in page->inode. As far as I understand
 * it, these are different when doing a swap-out.
 *
 * To understand everything that goes on here and in the NFS read code,
 * one should be aware that a page is locked in exactly one of the following
 * cases:
 *
 *  -   A write request is in progress.
 *  -   A user process is in generic_file_write/nfs_update_page
 *  -   A user process is in generic_file_read
 *
 * Also note that because of the way pages are invalidated in
 * nfs_revalidate_inode, the following assertions hold:
 *
 *  -   If a page is dirty, there will be no read requests (a page will
 *      not be re-read unless invalidated by nfs_revalidate_inode).
 *  -   If the page is not uptodate, there will be no pending write
 *      requests, and no process will be in nfs_update_page.
 *
 * FIXME: Interaction with the vmscan routines is not optimal yet.
 * Either vmscan must be made nfs-savvy, or we need a different page
 * reclaim concept that supports something like FS-independent
 * buffer_heads with a b_ops-> field.
 *
 * Copyright (C) 1996, 1997, Olaf Kirch <okir@monad.swb.de>
 */

#include <linux/types.h>
#include <linux/malloc.h>
#include <linux/swap.h>
#include <linux/pagemap.h>
#include <linux/file.h>

#include <linux/sunrpc/clnt.h>
#include <linux/nfs_fs.h>
#include <asm/uaccess.h>

#define NFS_PARANOIA 1
#define NFSDBG_FACILITY         NFSDBG_PAGECACHE

static void                     nfs_wback_begin(struct rpc_task *task);
static void                     nfs_wback_result(struct rpc_task *task);
static void                     nfs_cancel_request(struct nfs_wreq *req);

/*
 * Cache parameters
 */
#define NFS_WRITEBACK_DELAY     (10 * HZ)
#define NFS_WRITEBACK_MAX       64

/*
 * Limit number of delayed writes
 */
static int                      nr_write_requests = 0;
static struct rpc_wait_queue    write_queue = RPC_INIT_WAITQ("write_chain");

/* Hack for future NFS swap support */
#ifndef IS_SWAPFILE
# define IS_SWAPFILE(inode)     (0)
#endif

/*
 * Write a page synchronously.
 * Offset is the data offset within the page.
 */
static int
nfs_writepage_sync(struct dentry *dentry, struct inode *inode,
                struct page *page, unsigned long offset, unsigned int count)
{
        unsigned int    wsize = NFS_SERVER(inode)->wsize;
        int             result, refresh = 0, written = 0;
        u8              *buffer;
        struct nfs_fattr fattr;

        dprintk("NFS:      nfs_writepage_sync(%s/%s %d@%ld)\n",
                dentry->d_parent->d_name.name, dentry->d_name.name,
                count, page->offset + offset);

        buffer = (u8 *) page_address(page) + offset;
        offset += page->offset;

        do {
                if (count < wsize && !IS_SWAPFILE(inode))
                        wsize = count;

                result = nfs_proc_write(NFS_DSERVER(dentry), NFS_FH(dentry),
                                        IS_SWAPFILE(inode), offset, wsize,
                                        buffer, &fattr);

                if (result < 0) {
                        /* Must mark the page invalid after I/O error */
                        clear_bit(PG_uptodate, &page->flags);
                        goto io_error;
                }
                if (result != wsize)
                        printk("NFS: short write, wsize=%u, result=%d\n",
                        wsize, result);
                refresh = 1;
                buffer  += wsize;
                offset  += wsize;
                written += wsize;
                count   -= wsize;
                /*
                 * If we've extended the file, update the inode
                 * now so we don't invalidate the cache.
                 */
                if (offset > inode->i_size)
                        inode->i_size = offset;
        } while (count);

io_error:
        /* Note: we don't refresh if the call failed (fattr invalid) */
        if (refresh && result >= 0) {
                /* See comments in nfs_wback_result */
                /* N.B. I don't think this is right -- sync writes in order */
                if (fattr.size < inode->i_size)
                        fattr.size = inode->i_size;
                if (fattr.mtime.seconds < inode->i_mtime)
                        printk("nfs_writepage_sync: prior time??\n");
                /* Solaris 2.5 server seems to send garbled
                 * fattrs occasionally */
                if (inode->i_ino == fattr.fileid) {
                        /*
                         * We expect the mtime value to change, and
                         * don't want to invalidate the caches.
                         */
                        inode->i_mtime = fattr.mtime.seconds;
                        nfs_refresh_inode(inode, &fattr);
                } 
                else
                        printk("nfs_writepage_sync: inode %ld, got %u?\n",
                                inode->i_ino, fattr.fileid);
        }

        return written? written : result;
}

/*
 * Append a writeback request to a list
 */
static inline void
append_write_request(struct nfs_wreq **q, struct nfs_wreq *wreq)
{
        dprintk("NFS:      append_write_request(%p, %p)\n", q, wreq);
        rpc_append_list(q, wreq);
}

/*
 * Remove a writeback request from a list
 */
static inline void
remove_write_request(struct nfs_wreq **q, struct nfs_wreq *wreq)
{
        dprintk("NFS:      remove_write_request(%p, %p)\n", q, wreq);
        rpc_remove_list(q, wreq);
}

/*
 * Find a non-busy write request for a given page to
 * try to combine with.
 */
static inline struct nfs_wreq *
find_write_request(struct inode *inode, struct page *page)
{
        pid_t pid = current->pid;
        struct nfs_wreq *head, *req;

        dprintk("NFS:      find_write_request(%x/%ld, %p)\n",
                                inode->i_dev, inode->i_ino, page);
        if (!(req = head = NFS_WRITEBACK(inode)))
                return NULL;
        do {
                /*
                 * We can't combine with canceled requests or
                 * requests that have already been started..
                 */
                if (req->wb_flags & (NFS_WRITE_CANCELLED | NFS_WRITE_INPROGRESS))
                        continue;

                if (req->wb_page == page && req->wb_pid == pid)
                        return req;

                /*
                 * Ehh, don't keep too many tasks queued..
                 */
                rpc_wake_up_task(&req->wb_task);

        } while ((req = WB_NEXT(req)) != head);
        return NULL;
}

/*
 * Find and release all failed requests for this inode.
 */
int
nfs_check_failed_request(struct inode * inode)
{
        /* FIXME! */
        return 0;
}

/*
 * Try to merge adjacent write requests. This works only for requests
 * issued by the same user.
 */
static inline int
update_write_request(struct nfs_wreq *req, unsigned int first,
                        unsigned int bytes)
{
        unsigned int    rqfirst = req->wb_offset,
                        rqlast = rqfirst + req->wb_bytes,
                        last = first + bytes;

        dprintk("nfs:      trying to update write request %p\n", req);

        /* not contiguous? */
        if (rqlast < first || last < rqfirst)
                return 0;

        if (first < rqfirst)
                rqfirst = first;
        if (rqlast < last)
                rqlast = last;

        req->wb_offset = rqfirst;
        req->wb_bytes  = rqlast - rqfirst;
        req->wb_count++;

        return 1;
}

static kmem_cache_t *nfs_wreq_cachep;

int nfs_init_wreqcache(void)
{
        nfs_wreq_cachep = kmem_cache_create("nfs_wreq",
                                            sizeof(struct nfs_wreq),
                                            0, SLAB_HWCACHE_ALIGN,
                                            NULL, NULL);
        if (nfs_wreq_cachep == NULL)
                return -ENOMEM;
        return 0;
}

static inline void
free_write_request(struct nfs_wreq * req)
{
        if (!--req->wb_count)
                kmem_cache_free(nfs_wreq_cachep, req);
}

/*
 * Create and initialize a writeback request
 */
static inline struct nfs_wreq *
create_write_request(struct file * file, struct page *page, unsigned int offset, unsigned int bytes)
{
        struct dentry   *dentry = file->f_dentry;
        struct inode    *inode = dentry->d_inode;
        struct rpc_clnt *clnt = NFS_CLIENT(inode);
        struct nfs_wreq *wreq;
        struct rpc_task *task;

        dprintk("NFS:      create_write_request(%s/%s, %ld+%d)\n",
                dentry->d_parent->d_name.name, dentry->d_name.name,
                page->offset + offset, bytes);

        /* FIXME: Enforce hard limit on number of concurrent writes? */
        wreq = kmem_cache_alloc(nfs_wreq_cachep, SLAB_KERNEL);
        if (!wreq)
                goto out_fail;
        memset(wreq, 0, sizeof(*wreq));

        task = &wreq->wb_task;
        rpc_init_task(task, clnt, nfs_wback_result, RPC_TASK_NFSWRITE);
        task->tk_calldata = wreq;
        task->tk_action = nfs_wback_begin;

        rpcauth_lookupcred(task);       /* Obtain user creds */
        if (task->tk_status < 0)
                goto out_req;

        /* Put the task on inode's writeback request list. */
        wreq->wb_file = file;
        wreq->wb_pid    = current->pid;
        wreq->wb_page   = page;
        init_waitqueue_head(&wreq->wb_wait);
        wreq->wb_offset = offset;
        wreq->wb_bytes  = bytes;
        wreq->wb_count  = 2;            /* One for the IO, one for us */

        append_write_request(&NFS_WRITEBACK(inode), wreq);

        if (nr_write_requests++ > NFS_WRITEBACK_MAX*3/4)
                rpc_wake_up_next(&write_queue);

        return wreq;

out_req:
        rpc_release_task(task);
        kmem_cache_free(nfs_wreq_cachep, wreq);
out_fail:
        return NULL;
}

/*
 * Schedule a writeback RPC call.
 * If the server is congested, don't add to our backlog of queued
 * requests but call it synchronously.
 * The function returns whether we should wait for the thing or not.
 *
 * FIXME: Here we could walk the inode's lock list to see whether the
 * page we're currently writing to has been write-locked by the caller.
 * If it is, we could schedule an async write request with a long
 * delay in order to avoid writing back the page until the lock is
 * released.
 */
static inline int
schedule_write_request(struct nfs_wreq *req, int sync)
{
        struct rpc_task *task = &req->wb_task;
        struct file     *file = req->wb_file;
        struct dentry   *dentry = file->f_dentry;
        struct inode    *inode = dentry->d_inode;

        if (NFS_CONGESTED(inode) || nr_write_requests >= NFS_WRITEBACK_MAX)
                sync = 1;

        if (sync) {
                sigset_t        oldmask;
                struct rpc_clnt *clnt = NFS_CLIENT(inode);
                dprintk("NFS: %4d schedule_write_request (sync)\n",
                                        task->tk_pid);
                /* Page is already locked */
                rpc_clnt_sigmask(clnt, &oldmask);
                rpc_execute(task);
                rpc_clnt_sigunmask(clnt, &oldmask);
        } else {
                dprintk("NFS: %4d schedule_write_request (async)\n",
                                        task->tk_pid);
                task->tk_flags |= RPC_TASK_ASYNC;
                task->tk_timeout = NFS_WRITEBACK_DELAY;
                rpc_sleep_on(&write_queue, task, NULL, NULL);
        }

        return sync;
}

/*
 * Wait for request to complete.
 */
static int
wait_on_write_request(struct nfs_wreq *req)
{
        struct file             *file = req->wb_file;
        struct dentry           *dentry = file->f_dentry;
        struct inode            *inode = dentry->d_inode;
        struct rpc_clnt         *clnt = NFS_CLIENT(inode);
        DECLARE_WAITQUEUE(wait, current);
        sigset_t                oldmask;
        int retval;

        /* Make sure it's started.. */
        if (!WB_INPROGRESS(req))
                rpc_wake_up_task(&req->wb_task);

        rpc_clnt_sigmask(clnt, &oldmask);
        add_wait_queue(&req->wb_wait, &wait);
        for (;;) {
                current->state = TASK_INTERRUPTIBLE;
                retval = 0;
                if (req->wb_flags & NFS_WRITE_COMPLETE)
                        break;
                retval = -ERESTARTSYS;
                if (signalled())
                        break;
                schedule();
        }
        remove_wait_queue(&req->wb_wait, &wait);
        current->state = TASK_RUNNING;
        rpc_clnt_sigunmask(clnt, &oldmask);
        return retval;
}

/*
 * Write a page to the server. This will be used for NFS swapping only
 * (for now), and we currently do this synchronously only.
 */
int
nfs_writepage(struct file * file, struct page *page)
{
        struct dentry *dentry = file->f_dentry;
        return nfs_writepage_sync(dentry, dentry->d_inode, page, 0, PAGE_SIZE);
}

/*
 * Update and possibly write a cached page of an NFS file.
 *
 * XXX: Keep an eye on generic_file_read to make sure it doesn't do bad
 * things with a page scheduled for an RPC call (e.g. invalidate it).
 */
int
nfs_updatepage(struct file *file, struct page *page, unsigned long offset, unsigned int count)
{
        struct dentry   *dentry = file->f_dentry;
        struct inode    *inode = dentry->d_inode;
        struct nfs_wreq *req;
        int             synchronous = file->f_flags & O_SYNC;
        int             retval;

        dprintk("NFS:      nfs_updatepage(%s/%s %d@%ld)\n",
                dentry->d_parent->d_name.name, dentry->d_name.name,
                count, page->offset+offset);

        /*
         * Try to find a corresponding request on the writeback queue.
         * If there is one, we can be sure that this request is not
         * yet being processed, because we hold a lock on the page.
         *
         * If the request was created by us, update it. Otherwise,
         * transfer the page lock and flush out the dirty page now.
         * After returning, generic_file_write will wait on the
         * page and retry the update.
         */
        req = find_write_request(inode, page);
        if (req && req->wb_file == file && update_write_request(req, offset, count))
                goto updated;

        /*
         * If wsize is smaller than page size, update and write
         * page synchronously.
         */
        if (NFS_SERVER(inode)->wsize < PAGE_SIZE)
                return nfs_writepage_sync(dentry, inode, page, offset, count);

        /* Create the write request. */
        req = create_write_request(file, page, offset, count);
        if (!req)
                return -ENOBUFS;

        /*
         * Ok, there's another user of this page with the new request..
         * The IO completion will then free the page and the dentry.
         */
        atomic_inc(&page->count);
        file->f_count++;

        /* Schedule request */
        synchronous = schedule_write_request(req, synchronous);

updated:
        if (req->wb_bytes == PAGE_SIZE)
                set_bit(PG_uptodate, &page->flags);

        retval = count;
        if (synchronous) {
                int status = wait_on_write_request(req);
                if (status) {
                        nfs_cancel_request(req);
                        retval = status;
                } else {
                        status = req->wb_status;
                        if (status < 0)
                                retval = status;
                }

                if (retval < 0)
                        clear_bit(PG_uptodate, &page->flags);
        }

        free_write_request(req);
        return retval;
}

/*
 * Cancel a write request. We always mark it cancelled,
 * but if it's already in progress there's no point in
 * calling rpc_exit, and we don't want to overwrite the
 * tk_status field.
 */ 
static void
nfs_cancel_request(struct nfs_wreq *req)
{
        req->wb_flags |= NFS_WRITE_CANCELLED;
        if (!WB_INPROGRESS(req)) {
                rpc_exit(&req->wb_task, 0);
                rpc_wake_up_task(&req->wb_task);
        }
}

/*
 * Cancel all writeback requests, both pending and in progress.
 */
static void
nfs_cancel_dirty(struct inode *inode, pid_t pid)
{
        struct nfs_wreq *head, *req;

        req = head = NFS_WRITEBACK(inode);
        while (req != NULL) {
                if (pid == 0 || req->wb_pid == pid)
                        nfs_cancel_request(req);
                if ((req = WB_NEXT(req)) == head)
                        break;
        }
}

/*
 * If we're waiting on somebody else's request
 * we need to increment the counter during the
 * wait so that the request doesn't disappear
 * from under us during the wait..
 */
static int FASTCALL(wait_on_other_req(struct nfs_wreq *));
static int wait_on_other_req(struct nfs_wreq *req)
{
        int retval;
        req->wb_count++;
        retval = wait_on_write_request(req);
        free_write_request(req);
        return retval;
}

/*
 * This writes back a set of requests according to the condition.
 *
 * If this ever gets much more convoluted, use a fn pointer for
 * the condition..
 */
#define NFS_WB(inode, cond) { int retval = 0 ; \
        do { \
                struct nfs_wreq *req = NFS_WRITEBACK(inode); \
                struct nfs_wreq *head = req; \
                if (!req) break; \
                for (;;) { \
                        if (!(req->wb_flags & NFS_WRITE_COMPLETE)) \
                                if (cond) break; \
                        req = WB_NEXT(req); \
                        if (req == head) goto out; \
                } \
                retval = wait_on_other_req(req); \
        } while (!retval); \
out:    return retval; \
}

int
nfs_wb_all(struct inode *inode)
{
        NFS_WB(inode, 1);
}

/*
 * Write back all requests on one page - we do this before reading it.
 */
int
nfs_wb_page(struct inode *inode, struct page *page)
{
        NFS_WB(inode, req->wb_page == page);
}

/*
 * Write back all pending writes from one file descriptor..
 */
int
nfs_wb_file(struct inode *inode, struct file *file)
{
        NFS_WB(inode, req->wb_file == file);
}

void
nfs_inval(struct inode *inode)
{
        nfs_cancel_dirty(inode,0);
}

/*
 * The following procedures make up the writeback finite state machinery:
 *
 * 1.   Try to lock the page if not yet locked by us,
 *      set up the RPC call info, and pass to the call FSM.
 */
static void
nfs_wback_begin(struct rpc_task *task)
{
        struct nfs_wreq *req = (struct nfs_wreq *) task->tk_calldata;
        struct page     *page = req->wb_page;
        struct file     *file = req->wb_file;
        struct dentry   *dentry = file->f_dentry;

        dprintk("NFS: %4d nfs_wback_begin (%s/%s, status=%d flags=%x)\n",
                task->tk_pid, dentry->d_parent->d_name.name,
                dentry->d_name.name, task->tk_status, req->wb_flags);

        task->tk_status = 0;

        /* Setup the task struct for a writeback call */
        req->wb_flags |= NFS_WRITE_INPROGRESS;
        req->wb_args.fh     = NFS_FH(dentry);
        req->wb_args.offset = page->offset + req->wb_offset;
        req->wb_args.count  = req->wb_bytes;
        req->wb_args.buffer = (void *) (page_address(page) + req->wb_offset);

        rpc_call_setup(task, NFSPROC_WRITE, &req->wb_args, &req->wb_fattr, 0);

        return;
}

/*
 * 2.   Collect the result
 */
static void
nfs_wback_result(struct rpc_task *task)
{
        struct nfs_wreq *req = (struct nfs_wreq *) task->tk_calldata;
        struct file     *file = req->wb_file;
        struct page     *page = req->wb_page;
        int             status = task->tk_status;
        struct dentry   *dentry = file->f_dentry;
        struct inode    *inode = dentry->d_inode;

        dprintk("NFS: %4d nfs_wback_result (%s/%s, status=%d, flags=%x)\n",
                task->tk_pid, dentry->d_parent->d_name.name,
                dentry->d_name.name, status, req->wb_flags);

        /* Set the WRITE_COMPLETE flag, but leave WRITE_INPROGRESS set */
        req->wb_flags |= NFS_WRITE_COMPLETE;
        req->wb_status = status;

        if (status < 0) {
                req->wb_flags |= NFS_WRITE_INVALIDATE;
                file->f_error = status;
        } else if (!WB_CANCELLED(req)) {
                struct nfs_fattr *fattr = &req->wb_fattr;
                /* Update attributes as result of writeback. 
                 * Beware: when UDP replies arrive out of order, we
                 * may end up overwriting a previous, bigger file size.
                 *
                 * When the file size shrinks we cancel all pending
                 * writebacks. 
                 */
                if (fattr->mtime.seconds >= inode->i_mtime) {
                        if (fattr->size < inode->i_size)
                                fattr->size = inode->i_size;

                        /* possible Solaris 2.5 server bug workaround */
                        if (inode->i_ino == fattr->fileid) {
                                /*
                                 * We expect these values to change, and
                                 * don't want to invalidate the caches.
                                 */
                                inode->i_size  = fattr->size;
                                inode->i_mtime = fattr->mtime.seconds;
                                nfs_refresh_inode(inode, fattr);
                        }
                        else
                                printk("nfs_wback_result: inode %ld, got %u?\n",
                                        inode->i_ino, fattr->fileid);
                }
        }

        rpc_release_task(task);

        if (WB_INVALIDATE(req))
                clear_bit(PG_uptodate, &page->flags);

        __free_page(page);
        remove_write_request(&NFS_WRITEBACK(inode), req);
        nr_write_requests--;
        fput(req->wb_file);

        wake_up(&req->wb_wait);
        free_write_request(req);
}