/* NFS filesystem cache interface
*
* Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* 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 #include #include #include #include #include #include #include

#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,
struct nfs_clone_mount *mntdata)
{
struct nfs_fscache_key *key, *xkey;
struct nfs_server *nfss = NFS_SB(sb);
struct rb_node **p, *parent;
int diff, ulen;

if (uniq) {
ulen = strlen(uniq);
} else if (mntdata) {
struct nfs_server *mnt_s = NFS_SB(mntdata->sb);
if (mnt_s->fscache_key) {
uniq = mnt_s->fscache_key->key.uniquifier;
ulen = mnt_s->fscache_key->key.uniq_len;
}
}

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 invalidate any mapped pages that were read in before
* turning off the cache.
*/
if (inode->i_mapping && inode->i_mapping->nrpages)
invalidate_inode_pages2(inode->i_mapping);

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);
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)
{
struct nfs_inode *nfsi = NFS_I(page->mapping->host);
struct fscache_cookie *cookie = nfsi->fscache;

BUG_ON(!cookie);

if (PageFsCache(page)) {
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)
{
int ret, npages = *nr_pages;

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);
}
}

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