fs/nfs/fscache.c

0001 // SPDX-License-Identifier: GPL-2.0-or-later
0002 /* NFS filesystem cache interface
0003  *
0004  * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
0005  * Written by David Howells (dhowells@redhat.com)
0006  */
0007
0008 #include <linux/init.h>
0009 #include <linux/kernel.h>
0010 #include <linux/sched.h>
0011 #include <linux/mm.h>
0012 #include <linux/nfs_fs.h>
0013 #include <linux/nfs_fs_sb.h>
0014 #include <linux/in6.h>
0015 #include <linux/seq_file.h>
0016 #include <linux/slab.h>
0017 #include <linux/iversion.h>
0018
0019 #include "internal.h"
0020 #include "iostat.h"
0021 #include "fscache.h"
0022 #include "nfstrace.h"
0023
0024 #define NFS_MAX_KEY_LEN 1000
0025
0026 static bool nfs_append_int(char *key, int *_len, unsigned long long x)
0027 {
0028     if (*_len > NFS_MAX_KEY_LEN)
0029         return false;
0030     if (x == 0)
0031         key[(*_len)++] = ',';
0032     else
0033         *_len += sprintf(key + *_len, ",%llx", x);
0034     return true;
0035 }
0036
0037 /*
0038  * Get the per-client index cookie for an NFS client if the appropriate mount
0039  * flag was set
0040  * - We always try and get an index cookie for the client, but get filehandle
0041  *   cookies on a per-superblock basis, depending on the mount flags
0042  */
0043 static bool nfs_fscache_get_client_key(struct nfs_client *clp,
0044                        char *key, int *_len)
0045 {
0046     const struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *) &clp->cl_addr;
0047     const struct sockaddr_in *sin = (struct sockaddr_in *) &clp->cl_addr;
0048
0049     *_len += snprintf(key + *_len, NFS_MAX_KEY_LEN - *_len,
0050               ",%u.%u,%x",
0051               clp->rpc_ops->version,
0052               clp->cl_minorversion,
0053               clp->cl_addr.ss_family);
0054
0055     switch (clp->cl_addr.ss_family) {
0056     case AF_INET:
0057         if (!nfs_append_int(key, _len, sin->sin_port) ||
0058             !nfs_append_int(key, _len, sin->sin_addr.s_addr))
0059             return false;
0060         return true;
0061
0062     case AF_INET6:
0063         if (!nfs_append_int(key, _len, sin6->sin6_port) ||
0064             !nfs_append_int(key, _len, sin6->sin6_addr.s6_addr32[0]) ||
0065             !nfs_append_int(key, _len, sin6->sin6_addr.s6_addr32[1]) ||
0066             !nfs_append_int(key, _len, sin6->sin6_addr.s6_addr32[2]) ||
0067             !nfs_append_int(key, _len, sin6->sin6_addr.s6_addr32[3]))
0068             return false;
0069         return true;
0070
0071     default:
0072         printk(KERN_WARNING "NFS: Unknown network family '%d'\n",
0073                clp->cl_addr.ss_family);
0074         return false;
0075     }
0076 }
0077
0078 /*
0079  * Get the cache cookie for an NFS superblock.
0080  *
0081  * The default uniquifier is just an empty string, but it may be overridden
0082  * either by the 'fsc=xxx' option to mount, or by inheriting it from the parent
0083  * superblock across an automount point of some nature.
0084  */
0085 int nfs_fscache_get_super_cookie(struct super_block *sb, const char *uniq, int ulen)
0086 {
0087     struct fscache_volume *vcookie;
0088     struct nfs_server *nfss = NFS_SB(sb);
0089     unsigned int len = 3;
0090     char *key;
0091
0092     if (uniq) {
0093         nfss->fscache_uniq = kmemdup_nul(uniq, ulen, GFP_KERNEL);
0094         if (!nfss->fscache_uniq)
0095             return -ENOMEM;
0096     }
0097
0098     key = kmalloc(NFS_MAX_KEY_LEN + 24, GFP_KERNEL);
0099     if (!key)
0100         return -ENOMEM;
0101
0102     memcpy(key, "nfs", 3);
0103     if (!nfs_fscache_get_client_key(nfss->nfs_client, key, &len) ||
0104         !nfs_append_int(key, &len, nfss->fsid.major) ||
0105         !nfs_append_int(key, &len, nfss->fsid.minor) ||
0106         !nfs_append_int(key, &len, sb->s_flags & NFS_SB_MASK) ||
0107         !nfs_append_int(key, &len, nfss->flags) ||
0108         !nfs_append_int(key, &len, nfss->rsize) ||
0109         !nfs_append_int(key, &len, nfss->wsize) ||
0110         !nfs_append_int(key, &len, nfss->acregmin) ||
0111         !nfs_append_int(key, &len, nfss->acregmax) ||
0112         !nfs_append_int(key, &len, nfss->acdirmin) ||
0113         !nfs_append_int(key, &len, nfss->acdirmax) ||
0114         !nfs_append_int(key, &len, nfss->client->cl_auth->au_flavor))
0115         goto out;
0116
0117     if (ulen > 0) {
0118         if (ulen > NFS_MAX_KEY_LEN - len)
0119             goto out;
0120         key[len++] = ',';
0121         memcpy(key + len, uniq, ulen);
0122         len += ulen;
0123     }
0124     key[len] = 0;
0125
0126     /* create a cache index for looking up filehandles */
0127     vcookie = fscache_acquire_volume(key,
0128                      NULL, /* preferred_cache */
0129                      NULL, 0 /* coherency_data */);
0130     if (IS_ERR(vcookie)) {
0131         if (vcookie != ERR_PTR(-EBUSY)) {
0132             kfree(key);
0133             return PTR_ERR(vcookie);
0134         }
0135         pr_err("NFS: Cache volume key already in use (%s)\n", key);
0136         vcookie = NULL;
0137     }
0138     nfss->fscache = vcookie;
0139
0140 out:
0141     kfree(key);
0142     return 0;
0143 }
0144
0145 /*
0146  * release a per-superblock cookie
0147  */
0148 void nfs_fscache_release_super_cookie(struct super_block *sb)
0149 {
0150     struct nfs_server *nfss = NFS_SB(sb);
0151
0152     fscache_relinquish_volume(nfss->fscache, NULL, false);
0153     nfss->fscache = NULL;
0154     kfree(nfss->fscache_uniq);
0155 }
0156
0157 /*
0158  * Initialise the per-inode cache cookie pointer for an NFS inode.
0159  */
0160 void nfs_fscache_init_inode(struct inode *inode)
0161 {
0162     struct nfs_fscache_inode_auxdata auxdata;
0163     struct nfs_server *nfss = NFS_SERVER(inode);
0164     struct nfs_inode *nfsi = NFS_I(inode);
0165
0166     nfsi->fscache = NULL;
0167     if (!(nfss->fscache && S_ISREG(inode->i_mode)))
0168         return;
0169
0170     nfs_fscache_update_auxdata(&auxdata, inode);
0171
0172     nfsi->fscache = fscache_acquire_cookie(NFS_SB(inode->i_sb)->fscache,
0173                            0,
0174                            nfsi->fh.data, /* index_key */
0175                            nfsi->fh.size,
0176                            &auxdata,      /* aux_data */
0177                            sizeof(auxdata),
0178                            i_size_read(inode));
0179 }
0180
0181 /*
0182  * Release a per-inode cookie.
0183  */
0184 void nfs_fscache_clear_inode(struct inode *inode)
0185 {
0186     struct nfs_inode *nfsi = NFS_I(inode);
0187     struct fscache_cookie *cookie = nfs_i_fscache(inode);
0188
0189     fscache_relinquish_cookie(cookie, false);
0190     nfsi->fscache = NULL;
0191 }
0192
0193 /*
0194  * Enable or disable caching for a file that is being opened as appropriate.
0195  * The cookie is allocated when the inode is initialised, but is not enabled at
0196  * that time.  Enablement is deferred to file-open time to avoid stat() and
0197  * access() thrashing the cache.
0198  *
0199  * For now, with NFS, only regular files that are open read-only will be able
0200  * to use the cache.
0201  *
0202  * We enable the cache for an inode if we open it read-only and it isn't
0203  * currently open for writing.  We disable the cache if the inode is open
0204  * write-only.
0205  *
0206  * The caller uses the file struct to pin i_writecount on the inode before
0207  * calling us when a file is opened for writing, so we can make use of that.
0208  *
0209  * Note that this may be invoked multiple times in parallel by parallel
0210  * nfs_open() functions.
0211  */
0212 void nfs_fscache_open_file(struct inode *inode, struct file *filp)
0213 {
0214     struct nfs_fscache_inode_auxdata auxdata;
0215     struct fscache_cookie *cookie = nfs_i_fscache(inode);
0216     bool open_for_write = inode_is_open_for_write(inode);
0217
0218     if (!fscache_cookie_valid(cookie))
0219         return;
0220
0221     fscache_use_cookie(cookie, open_for_write);
0222     if (open_for_write) {
0223         nfs_fscache_update_auxdata(&auxdata, inode);
0224         fscache_invalidate(cookie, &auxdata, i_size_read(inode),
0225                    FSCACHE_INVAL_DIO_WRITE);
0226     }
0227 }
0228 EXPORT_SYMBOL_GPL(nfs_fscache_open_file);
0229
0230 void nfs_fscache_release_file(struct inode *inode, struct file *filp)
0231 {
0232     struct nfs_fscache_inode_auxdata auxdata;
0233     struct fscache_cookie *cookie = nfs_i_fscache(inode);
0234     loff_t i_size = i_size_read(inode);
0235
0236     nfs_fscache_update_auxdata(&auxdata, inode);
0237     fscache_unuse_cookie(cookie, &auxdata, &i_size);
0238 }
0239
0240 /*
0241  * Fallback page reading interface.
0242  */
0243 static int fscache_fallback_read_page(struct inode *inode, struct page *page)
0244 {
0245     struct netfs_cache_resources cres;
0246     struct fscache_cookie *cookie = nfs_i_fscache(inode);
0247     struct iov_iter iter;
0248     struct bio_vec bvec[1];
0249     int ret;
0250
0251     memset(&cres, 0, sizeof(cres));
0252     bvec[0].bv_page     = page;
0253     bvec[0].bv_offset   = 0;
0254     bvec[0].bv_len      = PAGE_SIZE;
0255     iov_iter_bvec(&iter, READ, bvec, ARRAY_SIZE(bvec), PAGE_SIZE);
0256
0257     ret = fscache_begin_read_operation(&cres, cookie);
0258     if (ret < 0)
0259         return ret;
0260
0261     ret = fscache_read(&cres, page_offset(page), &iter, NETFS_READ_HOLE_FAIL,
0262                NULL, NULL);
0263     fscache_end_operation(&cres);
0264     return ret;
0265 }
0266
0267 /*
0268  * Fallback page writing interface.
0269  */
0270 static int fscache_fallback_write_page(struct inode *inode, struct page *page,
0271                        bool no_space_allocated_yet)
0272 {
0273     struct netfs_cache_resources cres;
0274     struct fscache_cookie *cookie = nfs_i_fscache(inode);
0275     struct iov_iter iter;
0276     struct bio_vec bvec[1];
0277     loff_t start = page_offset(page);
0278     size_t len = PAGE_SIZE;
0279     int ret;
0280
0281     memset(&cres, 0, sizeof(cres));
0282     bvec[0].bv_page     = page;
0283     bvec[0].bv_offset   = 0;
0284     bvec[0].bv_len      = PAGE_SIZE;
0285     iov_iter_bvec(&iter, WRITE, bvec, ARRAY_SIZE(bvec), PAGE_SIZE);
0286
0287     ret = fscache_begin_write_operation(&cres, cookie);
0288     if (ret < 0)
0289         return ret;
0290
0291     ret = cres.ops->prepare_write(&cres, &start, &len, i_size_read(inode),
0292                       no_space_allocated_yet);
0293     if (ret == 0)
0294         ret = fscache_write(&cres, page_offset(page), &iter, NULL, NULL);
0295     fscache_end_operation(&cres);
0296     return ret;
0297 }
0298
0299 /*
0300  * Retrieve a page from fscache
0301  */
0302 int __nfs_fscache_read_page(struct inode *inode, struct page *page)
0303 {
0304     int ret;
0305
0306     trace_nfs_fscache_read_page(inode, page);
0307     if (PageChecked(page)) {
0308         ClearPageChecked(page);
0309         ret = 1;
0310         goto out;
0311     }
0312
0313     ret = fscache_fallback_read_page(inode, page);
0314     if (ret < 0) {
0315         nfs_inc_fscache_stats(inode, NFSIOS_FSCACHE_PAGES_READ_FAIL);
0316         SetPageChecked(page);
0317         goto out;
0318     }
0319
0320     /* Read completed synchronously */
0321     nfs_inc_fscache_stats(inode, NFSIOS_FSCACHE_PAGES_READ_OK);
0322     SetPageUptodate(page);
0323     ret = 0;
0324 out:
0325     trace_nfs_fscache_read_page_exit(inode, page, ret);
0326     return ret;
0327 }
0328
0329 /*
0330  * Store a newly fetched page in fscache.  We can be certain there's no page
0331  * stored in the cache as yet otherwise we would've read it from there.
0332  */
0333 void __nfs_fscache_write_page(struct inode *inode, struct page *page)
0334 {
0335     int ret;
0336
0337     trace_nfs_fscache_write_page(inode, page);
0338
0339     ret = fscache_fallback_write_page(inode, page, true);
0340
0341     if (ret != 0) {
0342         nfs_inc_fscache_stats(inode, NFSIOS_FSCACHE_PAGES_WRITTEN_FAIL);
0343         nfs_inc_fscache_stats(inode, NFSIOS_FSCACHE_PAGES_UNCACHED);
0344     } else {
0345         nfs_inc_fscache_stats(inode, NFSIOS_FSCACHE_PAGES_WRITTEN_OK);
0346     }
0347     trace_nfs_fscache_write_page_exit(inode, page, ret);
0348 }