fscache.c

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/* NFS filesystem cache interface
 *
 * Copyright (C) 2008 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 Licence
 * as published by the Free Software Foundation; either version
 * 2 of the Licence, or (at your option) any later version.
 */

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/nfs_fs.h>
#include <linux/nfs_fs_sb.h>
#include <linux/in6.h>
#include <linux/seq_file.h>
#include <linux/slab.h>

#include "internal.h"
#include "iostat.h"
#include "fscache.h"

#define NFSDBG_FACILITY     NFSDBG_FSCACHE

static struct rb_root nfs_fscache_keys = RB_ROOT;
static DEFINE_SPINLOCK(nfs_fscache_keys_lock);

/*
 * Get the per-client index cookie for an NFS client if the appropriate mount
 * flag was set
 * - We always try and get an index cookie for the client, but get filehandle
 *   cookies on a per-superblock basis, depending on the mount flags
 */
void nfs_fscache_get_client_cookie(struct nfs_client *clp)
{
    /* create a cache index for looking up filehandles */
    clp->fscache = fscache_acquire_cookie(nfs_fscache_netfs.primary_index,
                          &nfs_fscache_server_index_def,
                          clp);
    dfprintk(FSCACHE, "NFS: get client cookie (0x%p/0x%p)\n",
         clp, clp->fscache);
}

/*
 * Dispose of a per-client cookie
 */
void nfs_fscache_release_client_cookie(struct nfs_client *clp)
{
    dfprintk(FSCACHE, "NFS: releasing client cookie (0x%p/0x%p)\n",
         clp, clp->fscache);

    fscache_relinquish_cookie(clp->fscache, 0);
    clp->fscache = NULL;
}

/*
 * Get the cache cookie for an NFS superblock.  We have to handle
 * uniquification here because the cache doesn't do it for us.
 *
 * The default uniquifier is just an empty string, but it may be overridden
 * either by the 'fsc=xxx' option to mount, or by inheriting it from the parent
 * superblock across an automount point of some nature.
 */
void nfs_fscache_get_super_cookie(struct super_block *sb, const char *uniq, int ulen)
{
    struct nfs_fscache_key *key, *xkey;
    struct nfs_server *nfss = NFS_SB(sb);
    struct rb_node **p, *parent;
    int diff;

    if (!uniq) {
        uniq = "";
        ulen = 1;
    }

    key = kzalloc(sizeof(*key) + ulen, GFP_KERNEL);
    if (!key)
        return;

    key->nfs_client = nfss->nfs_client;
    key->key.super.s_flags = sb->s_flags & NFS_MS_MASK;
    key->key.nfs_server.flags = nfss->flags;
    key->key.nfs_server.rsize = nfss->rsize;
    key->key.nfs_server.wsize = nfss->wsize;
    key->key.nfs_server.acregmin = nfss->acregmin;
    key->key.nfs_server.acregmax = nfss->acregmax;
    key->key.nfs_server.acdirmin = nfss->acdirmin;
    key->key.nfs_server.acdirmax = nfss->acdirmax;
    key->key.nfs_server.fsid = nfss->fsid;
    key->key.rpc_auth.au_flavor = nfss->client->cl_auth->au_flavor;

    key->key.uniq_len = ulen;
    memcpy(key->key.uniquifier, uniq, ulen);

    spin_lock(&nfs_fscache_keys_lock);
    p = &nfs_fscache_keys.rb_node;
    parent = NULL;
    while (*p) {
        parent = *p;
        xkey = rb_entry(parent, struct nfs_fscache_key, node);

        if (key->nfs_client < xkey->nfs_client)
            goto go_left;
        if (key->nfs_client > xkey->nfs_client)
            goto go_right;

        diff = memcmp(&key->key, &xkey->key, sizeof(key->key));
        if (diff < 0)
            goto go_left;
        if (diff > 0)
            goto go_right;

        if (key->key.uniq_len == 0)
            goto non_unique;
        diff = memcmp(key->key.uniquifier,
                  xkey->key.uniquifier,
                  key->key.uniq_len);
        if (diff < 0)
            goto go_left;
        if (diff > 0)
            goto go_right;
        goto non_unique;

    go_left:
        p = &(*p)->rb_left;
        continue;
    go_right:
        p = &(*p)->rb_right;
    }

    rb_link_node(&key->node, parent, p);
    rb_insert_color(&key->node, &nfs_fscache_keys);
    spin_unlock(&nfs_fscache_keys_lock);
    nfss->fscache_key = key;

    /* create a cache index for looking up filehandles */
    nfss->fscache = fscache_acquire_cookie(nfss->nfs_client->fscache,
                           &nfs_fscache_super_index_def,
                           nfss);
    dfprintk(FSCACHE, "NFS: get superblock cookie (0x%p/0x%p)\n",
         nfss, nfss->fscache);
    return;

non_unique:
    spin_unlock(&nfs_fscache_keys_lock);
    kfree(key);
    nfss->fscache_key = NULL;
    nfss->fscache = NULL;
    printk(KERN_WARNING "NFS:"
           " Cache request denied due to non-unique superblock keys\n");
}

/*
 * release a per-superblock cookie
 */
void nfs_fscache_release_super_cookie(struct super_block *sb)
{
    struct nfs_server *nfss = NFS_SB(sb);

    dfprintk(FSCACHE, "NFS: releasing superblock cookie (0x%p/0x%p)\n",
         nfss, nfss->fscache);

    fscache_relinquish_cookie(nfss->fscache, 0);
    nfss->fscache = NULL;

    if (nfss->fscache_key) {
        spin_lock(&nfs_fscache_keys_lock);
        rb_erase(&nfss->fscache_key->node, &nfs_fscache_keys);
        spin_unlock(&nfs_fscache_keys_lock);
        kfree(nfss->fscache_key);
        nfss->fscache_key = NULL;
    }
}

/*
 * Initialise the per-inode cache cookie pointer for an NFS inode.
 */
void nfs_fscache_init_inode_cookie(struct inode *inode)
{
    NFS_I(inode)->fscache = NULL;
    if (S_ISREG(inode->i_mode))
        set_bit(NFS_INO_FSCACHE, &NFS_I(inode)->flags);
}

/*
 * Get the per-inode cache cookie for an NFS inode.
 */
static void nfs_fscache_enable_inode_cookie(struct inode *inode)
{
    struct super_block *sb = inode->i_sb;
    struct nfs_inode *nfsi = NFS_I(inode);

    if (nfsi->fscache || !NFS_FSCACHE(inode))
        return;

    if ((NFS_SB(sb)->options & NFS_OPTION_FSCACHE)) {
        nfsi->fscache = fscache_acquire_cookie(
            NFS_SB(sb)->fscache,
            &nfs_fscache_inode_object_def,
            nfsi);

        dfprintk(FSCACHE, "NFS: get FH cookie (0x%p/0x%p/0x%p)\n",
             sb, nfsi, nfsi->fscache);
    }
}

/*
 * Release a per-inode cookie.
 */
void nfs_fscache_release_inode_cookie(struct inode *inode)
{
    struct nfs_inode *nfsi = NFS_I(inode);

    dfprintk(FSCACHE, "NFS: clear cookie (0x%p/0x%p)\n",
         nfsi, nfsi->fscache);

    fscache_relinquish_cookie(nfsi->fscache, 0);
    nfsi->fscache = NULL;
}

/*
 * Retire a per-inode cookie, destroying the data attached to it.
 */
void nfs_fscache_zap_inode_cookie(struct inode *inode)
{
    struct nfs_inode *nfsi = NFS_I(inode);

    dfprintk(FSCACHE, "NFS: zapping cookie (0x%p/0x%p)\n",
         nfsi, nfsi->fscache);

    fscache_relinquish_cookie(nfsi->fscache, 1);
    nfsi->fscache = NULL;
}

/*
 * Turn off the cache with regard to a per-inode cookie if opened for writing,
 * invalidating all the pages in the page cache relating to the associated
 * inode to clear the per-page caching.
 */
static void nfs_fscache_disable_inode_cookie(struct inode *inode)
{
    clear_bit(NFS_INO_FSCACHE, &NFS_I(inode)->flags);

    if (NFS_I(inode)->fscache) {
        dfprintk(FSCACHE,
             "NFS: nfsi 0x%p turning cache off\n", NFS_I(inode));

        /* Need to uncache any pages attached to this inode that
         * fscache knows about before turning off the cache.
         */
        fscache_uncache_all_inode_pages(NFS_I(inode)->fscache, inode);
        nfs_fscache_zap_inode_cookie(inode);
    }
}

/*
 * wait_on_bit() sleep function for uninterruptible waiting
 */
static int nfs_fscache_wait_bit(void *flags)
{
    schedule();
    return 0;
}

/*
 * Lock against someone else trying to also acquire or relinquish a cookie
 */
static inline void nfs_fscache_inode_lock(struct inode *inode)
{
    struct nfs_inode *nfsi = NFS_I(inode);

    while (test_and_set_bit(NFS_INO_FSCACHE_LOCK, &nfsi->flags))
        wait_on_bit(&nfsi->flags, NFS_INO_FSCACHE_LOCK,
                nfs_fscache_wait_bit, TASK_UNINTERRUPTIBLE);
}

/*
 * Unlock cookie management lock
 */
static inline void nfs_fscache_inode_unlock(struct inode *inode)
{
    struct nfs_inode *nfsi = NFS_I(inode);

    smp_mb__before_clear_bit();
    clear_bit(NFS_INO_FSCACHE_LOCK, &nfsi->flags);
    smp_mb__after_clear_bit();
    wake_up_bit(&nfsi->flags, NFS_INO_FSCACHE_LOCK);
}

/*
 * Decide if we should enable or disable local caching for this inode.
 * - For now, with NFS, only regular files that are open read-only will be able
 *   to use the cache.
 * - May be invoked multiple times in parallel by parallel nfs_open() functions.
 */
void nfs_fscache_set_inode_cookie(struct inode *inode, struct file *filp)
{
    if (NFS_FSCACHE(inode)) {
        nfs_fscache_inode_lock(inode);
        if ((filp->f_flags & O_ACCMODE) != O_RDONLY)
            nfs_fscache_disable_inode_cookie(inode);
        else
            nfs_fscache_enable_inode_cookie(inode);
        nfs_fscache_inode_unlock(inode);
    }
}

/*
 * Replace a per-inode cookie due to revalidation detecting a file having
 * changed on the server.
 */
void nfs_fscache_reset_inode_cookie(struct inode *inode)
{
    struct nfs_inode *nfsi = NFS_I(inode);
    struct nfs_server *nfss = NFS_SERVER(inode);
    NFS_IFDEBUG(struct fscache_cookie *old = nfsi->fscache);

    nfs_fscache_inode_lock(inode);
    if (nfsi->fscache) {
        /* retire the current fscache cache and get a new one */
        fscache_relinquish_cookie(nfsi->fscache, 1);

        nfsi->fscache = fscache_acquire_cookie(
            nfss->nfs_client->fscache,
            &nfs_fscache_inode_object_def,
            nfsi);

        dfprintk(FSCACHE,
             "NFS: revalidation new cookie (0x%p/0x%p/0x%p/0x%p)\n",
             nfss, nfsi, old, nfsi->fscache);
    }
    nfs_fscache_inode_unlock(inode);
}

/*
 * Release the caching state associated with a page, if the page isn't busy
 * interacting with the cache.
 * - Returns true (can release page) or false (page busy).
 */
int nfs_fscache_release_page(struct page *page, gfp_t gfp)
{
    if (PageFsCache(page)) {
        struct nfs_inode *nfsi = NFS_I(page->mapping->host);
        struct fscache_cookie *cookie = nfsi->fscache;

        BUG_ON(!cookie);
        dfprintk(FSCACHE, "NFS: fscache releasepage (0x%p/0x%p/0x%p)\n",
             cookie, page, nfsi);

        if (!fscache_maybe_release_page(cookie, page, gfp))
            return 0;

        nfs_add_fscache_stats(page->mapping->host,
                      NFSIOS_FSCACHE_PAGES_UNCACHED, 1);
    }

    return 1;
}

/*
 * Release the caching state associated with a page if undergoing complete page
 * invalidation.
 */
void __nfs_fscache_invalidate_page(struct page *page, struct inode *inode)
{
    struct nfs_inode *nfsi = NFS_I(inode);
    struct fscache_cookie *cookie = nfsi->fscache;

    BUG_ON(!cookie);

    dfprintk(FSCACHE, "NFS: fscache invalidatepage (0x%p/0x%p/0x%p)\n",
         cookie, page, nfsi);

    fscache_wait_on_page_write(cookie, page);

    BUG_ON(!PageLocked(page));
    fscache_uncache_page(cookie, page);
    nfs_add_fscache_stats(page->mapping->host,
                  NFSIOS_FSCACHE_PAGES_UNCACHED, 1);
}

/*
 * Handle completion of a page being read from the cache.
 * - Called in process (keventd) context.
 */
static void nfs_readpage_from_fscache_complete(struct page *page,
                           void *context,
                           int error)
{
    dfprintk(FSCACHE,
         "NFS: readpage_from_fscache_complete (0x%p/0x%p/%d)\n",
         page, context, 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);
    } else {
        error = nfs_readpage_async(context, page->mapping->host, page);
        if (error)
            unlock_page(page);
    }
}

/*
 * Retrieve a page from fscache
 */
int __nfs_readpage_from_fscache(struct nfs_open_context *ctx,
                struct inode *inode, struct page *page)
{
    int ret;

    dfprintk(FSCACHE,
         "NFS: readpage_from_fscache(fsc:%p/p:%p(i:%lx f:%lx)/0x%p)\n",
         NFS_I(inode)->fscache, page, page->index, page->flags, inode);

    ret = fscache_read_or_alloc_page(NFS_I(inode)->fscache,
                     page,
                     nfs_readpage_from_fscache_complete,
                     ctx,
                     GFP_KERNEL);

    switch (ret) {
    case 0: /* read BIO submitted (page in fscache) */
        dfprintk(FSCACHE,
             "NFS:    readpage_from_fscache: BIO submitted\n");
        nfs_add_fscache_stats(inode, NFSIOS_FSCACHE_PAGES_READ_OK, 1);
        return ret;

    case -ENOBUFS: /* inode not in cache */
    case -ENODATA: /* page not in cache */
        nfs_add_fscache_stats(inode, NFSIOS_FSCACHE_PAGES_READ_FAIL, 1);
        dfprintk(FSCACHE,
             "NFS:    readpage_from_fscache %d\n", ret);
        return 1;

    default:
        dfprintk(FSCACHE, "NFS:    readpage_from_fscache %d\n", ret);
        nfs_add_fscache_stats(inode, NFSIOS_FSCACHE_PAGES_READ_FAIL, 1);
    }
    return ret;
}

/*
 * Retrieve a set of pages from fscache
 */
int __nfs_readpages_from_fscache(struct nfs_open_context *ctx,
                 struct inode *inode,
                 struct address_space *mapping,
                 struct list_head *pages,
                 unsigned *nr_pages)
{
    unsigned npages = *nr_pages;
    int ret;

    dfprintk(FSCACHE, "NFS: nfs_getpages_from_fscache (0x%p/%u/0x%p)\n",
         NFS_I(inode)->fscache, npages, inode);

    ret = fscache_read_or_alloc_pages(NFS_I(inode)->fscache,
                      mapping, pages, nr_pages,
                      nfs_readpage_from_fscache_complete,
                      ctx,
                      mapping_gfp_mask(mapping));
    if (*nr_pages < npages)
        nfs_add_fscache_stats(inode, NFSIOS_FSCACHE_PAGES_READ_OK,
                      npages);
    if (*nr_pages > 0)
        nfs_add_fscache_stats(inode, NFSIOS_FSCACHE_PAGES_READ_FAIL,
                      *nr_pages);

    switch (ret) {
    case 0: /* read submitted to the cache for all pages */
        BUG_ON(!list_empty(pages));
        BUG_ON(*nr_pages != 0);
        dfprintk(FSCACHE,
             "NFS: nfs_getpages_from_fscache: submitted\n");

        return ret;

    case -ENOBUFS: /* some pages aren't cached and can't be */
    case -ENODATA: /* some pages aren't cached */
        dfprintk(FSCACHE,
             "NFS: nfs_getpages_from_fscache: no page: %d\n", ret);
        return 1;

    default:
        dfprintk(FSCACHE,
             "NFS: nfs_getpages_from_fscache: ret  %d\n", ret);
    }

    return ret;
}

/*
 * Store a newly fetched page in fscache
 * - PG_fscache must be set on the page
 */
void __nfs_readpage_to_fscache(struct inode *inode, struct page *page, int sync)
{
    int ret;

    dfprintk(FSCACHE,
         "NFS: readpage_to_fscache(fsc:%p/p:%p(i:%lx f:%lx)/%d)\n",
         NFS_I(inode)->fscache, page, page->index, page->flags, sync);

    ret = fscache_write_page(NFS_I(inode)->fscache, page, GFP_KERNEL);
    dfprintk(FSCACHE,
         "NFS:     readpage_to_fscache: p:%p(i:%lu f:%lx) ret %d\n",
         page, page->index, page->flags, ret);

    if (ret != 0) {
        fscache_uncache_page(NFS_I(inode)->fscache, page);
        nfs_add_fscache_stats(inode,
                      NFSIOS_FSCACHE_PAGES_WRITTEN_FAIL, 1);
        nfs_add_fscache_stats(inode, NFSIOS_FSCACHE_PAGES_UNCACHED, 1);
    } else {
        nfs_add_fscache_stats(inode,
                      NFSIOS_FSCACHE_PAGES_WRITTEN_OK, 1);
    }
}