file.c

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/* AFS filesystem file handling
 *
 * Copyright (C) 2002, 2007 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells ([email protected])
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/pagemap.h>
#include <linux/writeback.h>
#include <linux/gfp.h>
#include "internal.h"

static int afs_readpage(struct file *file, struct page *page);
static void afs_invalidatepage(struct page *page, unsigned long offset);
static int afs_releasepage(struct page *page, gfp_t gfp_flags);
static int afs_launder_page(struct page *page);

static int afs_readpages(struct file *filp, struct address_space *mapping,
             struct list_head *pages, unsigned nr_pages);

const struct file_operations afs_file_operations = {
    .open       = afs_open,
    .release    = afs_release,
    .llseek     = generic_file_llseek,
    .read       = do_sync_read,
    .write      = do_sync_write,
    .aio_read   = generic_file_aio_read,
    .aio_write  = afs_file_write,
    .mmap       = generic_file_readonly_mmap,
    .splice_read    = generic_file_splice_read,
    .fsync      = afs_fsync,
    .lock       = afs_lock,
    .flock      = afs_flock,
};

const struct inode_operations afs_file_inode_operations = {
    .getattr    = afs_getattr,
    .setattr    = afs_setattr,
    .permission = afs_permission,
};

const struct address_space_operations afs_fs_aops = {
    .readpage   = afs_readpage,
    .readpages  = afs_readpages,
    .set_page_dirty = afs_set_page_dirty,
    .launder_page   = afs_launder_page,
    .releasepage    = afs_releasepage,
    .invalidatepage = afs_invalidatepage,
    .write_begin    = afs_write_begin,
    .write_end  = afs_write_end,
    .writepage  = afs_writepage,
    .writepages = afs_writepages,
};

/*
 * open an AFS file or directory and attach a key to it
 */
int afs_open(struct inode *inode, struct file *file)
{
    struct afs_vnode *vnode = AFS_FS_I(inode);
    struct key *key;
    int ret;

    _enter("{%x:%u},", vnode->fid.vid, vnode->fid.vnode);

    key = afs_request_key(vnode->volume->cell);
    if (IS_ERR(key)) {
        _leave(" = %ld [key]", PTR_ERR(key));
        return PTR_ERR(key);
    }

    ret = afs_validate(vnode, key);
    if (ret < 0) {
        _leave(" = %d [val]", ret);
        return ret;
    }

    file->private_data = key;
    _leave(" = 0");
    return 0;
}

/*
 * release an AFS file or directory and discard its key
 */
int afs_release(struct inode *inode, struct file *file)
{
    struct afs_vnode *vnode = AFS_FS_I(inode);

    _enter("{%x:%u},", vnode->fid.vid, vnode->fid.vnode);

    key_put(file->private_data);
    _leave(" = 0");
    return 0;
}

#ifdef CONFIG_AFS_FSCACHE
/*
 * deal with notification that a page was read from the cache
 */
static void afs_file_readpage_read_complete(struct page *page,
                        void *data,
                        int error)
{
    _enter("%p,%p,%d", page, data, error);

    /* if the read completes with an error, we just unlock the page and let
     * the VM reissue the readpage */
    if (!error)
        SetPageUptodate(page);
    unlock_page(page);
}
#endif

/*
 * read page from file, directory or symlink, given a key to use
 */
int afs_page_filler(void *data, struct page *page)
{
    struct inode *inode = page->mapping->host;
    struct afs_vnode *vnode = AFS_FS_I(inode);
    struct key *key = data;
    size_t len;
    off_t offset;
    int ret;

    _enter("{%x},{%lu},{%lu}", key_serial(key), inode->i_ino, page->index);

    BUG_ON(!PageLocked(page));

    ret = -ESTALE;
    if (test_bit(AFS_VNODE_DELETED, &vnode->flags))
        goto error;

    /* is it cached? */
#ifdef CONFIG_AFS_FSCACHE
    ret = fscache_read_or_alloc_page(vnode->cache,
                     page,
                     afs_file_readpage_read_complete,
                     NULL,
                     GFP_KERNEL);
#else
    ret = -ENOBUFS;
#endif
    switch (ret) {
        /* read BIO submitted (page in cache) */
    case 0:
        break;

        /* page not yet cached */
    case -ENODATA:
        _debug("cache said ENODATA");
        goto go_on;

        /* page will not be cached */
    case -ENOBUFS:
        _debug("cache said ENOBUFS");
    default:
    go_on:
        offset = page->index << PAGE_CACHE_SHIFT;
        len = min_t(size_t, i_size_read(inode) - offset, PAGE_SIZE);

        /* read the contents of the file from the server into the
         * page */
        ret = afs_vnode_fetch_data(vnode, key, offset, len, page);
        if (ret < 0) {
            if (ret == -ENOENT) {
                _debug("got NOENT from server"
                       " - marking file deleted and stale");
                set_bit(AFS_VNODE_DELETED, &vnode->flags);
                ret = -ESTALE;
            }

#ifdef CONFIG_AFS_FSCACHE
            fscache_uncache_page(vnode->cache, page);
#endif
            BUG_ON(PageFsCache(page));
            goto error;
        }

        SetPageUptodate(page);

        /* send the page to the cache */
#ifdef CONFIG_AFS_FSCACHE
        if (PageFsCache(page) &&
            fscache_write_page(vnode->cache, page, GFP_KERNEL) != 0) {
            fscache_uncache_page(vnode->cache, page);
            BUG_ON(PageFsCache(page));
        }
#endif
        unlock_page(page);
    }

    _leave(" = 0");
    return 0;

error:
    SetPageError(page);
    unlock_page(page);
    _leave(" = %d", ret);
    return ret;
}

/*
 * read page from file, directory or symlink, given a file to nominate the key
 * to be used
 */
static int afs_readpage(struct file *file, struct page *page)
{
    struct key *key;
    int ret;

    if (file) {
        key = file->private_data;
        ASSERT(key != NULL);
        ret = afs_page_filler(key, page);
    } else {
        struct inode *inode = page->mapping->host;
        key = afs_request_key(AFS_FS_S(inode->i_sb)->volume->cell);
        if (IS_ERR(key)) {
            ret = PTR_ERR(key);
        } else {
            ret = afs_page_filler(key, page);
            key_put(key);
        }
    }
    return ret;
}

/*
 * read a set of pages
 */
static int afs_readpages(struct file *file, struct address_space *mapping,
             struct list_head *pages, unsigned nr_pages)
{
    struct key *key = file->private_data;
    struct afs_vnode *vnode;
    int ret = 0;

    _enter("{%d},{%lu},,%d",
           key_serial(key), mapping->host->i_ino, nr_pages);

    ASSERT(key != NULL);

    vnode = AFS_FS_I(mapping->host);
    if (test_bit(AFS_VNODE_DELETED, &vnode->flags)) {
        _leave(" = -ESTALE");
        return -ESTALE;
    }

    /* attempt to read as many of the pages as possible */
#ifdef CONFIG_AFS_FSCACHE
    ret = fscache_read_or_alloc_pages(vnode->cache,
                      mapping,
                      pages,
                      &nr_pages,
                      afs_file_readpage_read_complete,
                      NULL,
                      mapping_gfp_mask(mapping));
#else
    ret = -ENOBUFS;
#endif

    switch (ret) {
        /* all pages are being read from the cache */
    case 0:
        BUG_ON(!list_empty(pages));
        BUG_ON(nr_pages != 0);
        _leave(" = 0 [reading all]");
        return 0;

        /* there were pages that couldn't be read from the cache */
    case -ENODATA:
    case -ENOBUFS:
        break;

        /* other error */
    default:
        _leave(" = %d", ret);
        return ret;
    }

    /* load the missing pages from the network */
    ret = read_cache_pages(mapping, pages, afs_page_filler, key);

    _leave(" = %d [netting]", ret);
    return ret;
}

/*
 * write back a dirty page
 */
static int afs_launder_page(struct page *page)
{
    _enter("{%lu}", page->index);

    return 0;
}

/*
 * invalidate part or all of a page
 * - release a page and clean up its private data if offset is 0 (indicating
 *   the entire page)
 */
static void afs_invalidatepage(struct page *page, unsigned long offset)
{
    struct afs_writeback *wb = (struct afs_writeback *) page_private(page);

    _enter("{%lu},%lu", page->index, offset);

    BUG_ON(!PageLocked(page));

    /* we clean up only if the entire page is being invalidated */
    if (offset == 0) {
#ifdef CONFIG_AFS_FSCACHE
        if (PageFsCache(page)) {
            struct afs_vnode *vnode = AFS_FS_I(page->mapping->host);
            fscache_wait_on_page_write(vnode->cache, page);
            fscache_uncache_page(vnode->cache, page);
        }
#endif

        if (PagePrivate(page)) {
            if (wb && !PageWriteback(page)) {
                set_page_private(page, 0);
                afs_put_writeback(wb);
            }

            if (!page_private(page))
                ClearPagePrivate(page);
        }
    }

    _leave("");
}

/*
 * release a page and clean up its private state if it's not busy
 * - return true if the page can now be released, false if not
 */
static int afs_releasepage(struct page *page, gfp_t gfp_flags)
{
    struct afs_writeback *wb = (struct afs_writeback *) page_private(page);
    struct afs_vnode *vnode = AFS_FS_I(page->mapping->host);

    _enter("{{%x:%u}[%lu],%lx},%x",
           vnode->fid.vid, vnode->fid.vnode, page->index, page->flags,
           gfp_flags);

    /* deny if page is being written to the cache and the caller hasn't
     * elected to wait */
#ifdef CONFIG_AFS_FSCACHE
    if (!fscache_maybe_release_page(vnode->cache, page, gfp_flags)) {
        _leave(" = F [cache busy]");
        return 0;
    }
#endif

    if (PagePrivate(page)) {
        if (wb) {
            set_page_private(page, 0);
            afs_put_writeback(wb);
        }
        ClearPagePrivate(page);
    }

    /* indicate that the page can be released */
    _leave(" = T");
    return 1;
}