linux/fs/nfs/read.c
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   1/*
   2 * linux/fs/nfs/read.c
   3 *
   4 * Block I/O for NFS
   5 *
   6 * Partial copy of Linus' read cache modifications to fs/nfs/file.c
   7 * modified for async RPC by okir@monad.swb.de
   8 */
   9
  10#include <linux/time.h>
  11#include <linux/kernel.h>
  12#include <linux/errno.h>
  13#include <linux/fcntl.h>
  14#include <linux/stat.h>
  15#include <linux/mm.h>
  16#include <linux/slab.h>
  17#include <linux/pagemap.h>
  18#include <linux/sunrpc/clnt.h>
  19#include <linux/nfs_fs.h>
  20#include <linux/nfs_page.h>
  21#include <linux/module.h>
  22
  23#include "nfs4_fs.h"
  24#include "internal.h"
  25#include "iostat.h"
  26#include "fscache.h"
  27#include "pnfs.h"
  28
  29#define NFSDBG_FACILITY         NFSDBG_PAGECACHE
  30
  31static const struct nfs_pgio_completion_ops nfs_async_read_completion_ops;
  32static const struct nfs_rw_ops nfs_rw_read_ops;
  33
  34static struct kmem_cache *nfs_rdata_cachep;
  35
  36static struct nfs_pgio_header *nfs_readhdr_alloc(void)
  37{
  38        return kmem_cache_zalloc(nfs_rdata_cachep, GFP_KERNEL);
  39}
  40
  41static void nfs_readhdr_free(struct nfs_pgio_header *rhdr)
  42{
  43        kmem_cache_free(nfs_rdata_cachep, rhdr);
  44}
  45
  46static
  47int nfs_return_empty_page(struct page *page)
  48{
  49        zero_user(page, 0, PAGE_SIZE);
  50        SetPageUptodate(page);
  51        unlock_page(page);
  52        return 0;
  53}
  54
  55void nfs_pageio_init_read(struct nfs_pageio_descriptor *pgio,
  56                              struct inode *inode, bool force_mds,
  57                              const struct nfs_pgio_completion_ops *compl_ops)
  58{
  59        struct nfs_server *server = NFS_SERVER(inode);
  60        const struct nfs_pageio_ops *pg_ops = &nfs_pgio_rw_ops;
  61
  62#ifdef CONFIG_NFS_V4_1
  63        if (server->pnfs_curr_ld && !force_mds)
  64                pg_ops = server->pnfs_curr_ld->pg_read_ops;
  65#endif
  66        nfs_pageio_init(pgio, inode, pg_ops, compl_ops, &nfs_rw_read_ops,
  67                        server->rsize, 0);
  68}
  69EXPORT_SYMBOL_GPL(nfs_pageio_init_read);
  70
  71void nfs_pageio_reset_read_mds(struct nfs_pageio_descriptor *pgio)
  72{
  73        struct nfs_pgio_mirror *mirror;
  74
  75        if (pgio->pg_ops && pgio->pg_ops->pg_cleanup)
  76                pgio->pg_ops->pg_cleanup(pgio);
  77
  78        pgio->pg_ops = &nfs_pgio_rw_ops;
  79
  80        /* read path should never have more than one mirror */
  81        WARN_ON_ONCE(pgio->pg_mirror_count != 1);
  82
  83        mirror = &pgio->pg_mirrors[0];
  84        mirror->pg_bsize = NFS_SERVER(pgio->pg_inode)->rsize;
  85}
  86EXPORT_SYMBOL_GPL(nfs_pageio_reset_read_mds);
  87
  88static void nfs_readpage_release(struct nfs_page *req)
  89{
  90        struct inode *inode = d_inode(req->wb_context->dentry);
  91
  92        dprintk("NFS: read done (%s/%llu %d@%lld)\n", inode->i_sb->s_id,
  93                (unsigned long long)NFS_FILEID(inode), req->wb_bytes,
  94                (long long)req_offset(req));
  95
  96        if (nfs_page_group_sync_on_bit(req, PG_UNLOCKPAGE)) {
  97                if (PageUptodate(req->wb_page))
  98                        nfs_readpage_to_fscache(inode, req->wb_page, 0);
  99
 100                unlock_page(req->wb_page);
 101        }
 102        nfs_release_request(req);
 103}
 104
 105int nfs_readpage_async(struct nfs_open_context *ctx, struct inode *inode,
 106                       struct page *page)
 107{
 108        struct nfs_page *new;
 109        unsigned int len;
 110        struct nfs_pageio_descriptor pgio;
 111        struct nfs_pgio_mirror *pgm;
 112
 113        len = nfs_page_length(page);
 114        if (len == 0)
 115                return nfs_return_empty_page(page);
 116        new = nfs_create_request(ctx, page, NULL, 0, len);
 117        if (IS_ERR(new)) {
 118                unlock_page(page);
 119                return PTR_ERR(new);
 120        }
 121        if (len < PAGE_SIZE)
 122                zero_user_segment(page, len, PAGE_SIZE);
 123
 124        nfs_pageio_init_read(&pgio, inode, false,
 125                             &nfs_async_read_completion_ops);
 126        if (!nfs_pageio_add_request(&pgio, new)) {
 127                nfs_list_remove_request(new);
 128                nfs_readpage_release(new);
 129        }
 130        nfs_pageio_complete(&pgio);
 131
 132        /* It doesn't make sense to do mirrored reads! */
 133        WARN_ON_ONCE(pgio.pg_mirror_count != 1);
 134
 135        pgm = &pgio.pg_mirrors[0];
 136        NFS_I(inode)->read_io += pgm->pg_bytes_written;
 137
 138        return pgio.pg_error < 0 ? pgio.pg_error : 0;
 139}
 140
 141static void nfs_page_group_set_uptodate(struct nfs_page *req)
 142{
 143        if (nfs_page_group_sync_on_bit(req, PG_UPTODATE))
 144                SetPageUptodate(req->wb_page);
 145}
 146
 147static void nfs_read_completion(struct nfs_pgio_header *hdr)
 148{
 149        unsigned long bytes = 0;
 150
 151        if (test_bit(NFS_IOHDR_REDO, &hdr->flags))
 152                goto out;
 153        while (!list_empty(&hdr->pages)) {
 154                struct nfs_page *req = nfs_list_entry(hdr->pages.next);
 155                struct page *page = req->wb_page;
 156                unsigned long start = req->wb_pgbase;
 157                unsigned long end = req->wb_pgbase + req->wb_bytes;
 158
 159                if (test_bit(NFS_IOHDR_EOF, &hdr->flags)) {
 160                        /* note: regions of the page not covered by a
 161                         * request are zeroed in nfs_readpage_async /
 162                         * readpage_async_filler */
 163                        if (bytes > hdr->good_bytes) {
 164                                /* nothing in this request was good, so zero
 165                                 * the full extent of the request */
 166                                zero_user_segment(page, start, end);
 167
 168                        } else if (hdr->good_bytes - bytes < req->wb_bytes) {
 169                                /* part of this request has good bytes, but
 170                                 * not all. zero the bad bytes */
 171                                start += hdr->good_bytes - bytes;
 172                                WARN_ON(start < req->wb_pgbase);
 173                                zero_user_segment(page, start, end);
 174                        }
 175                }
 176                bytes += req->wb_bytes;
 177                if (test_bit(NFS_IOHDR_ERROR, &hdr->flags)) {
 178                        if (bytes <= hdr->good_bytes)
 179                                nfs_page_group_set_uptodate(req);
 180                } else
 181                        nfs_page_group_set_uptodate(req);
 182                nfs_list_remove_request(req);
 183                nfs_readpage_release(req);
 184        }
 185out:
 186        hdr->release(hdr);
 187}
 188
 189static void nfs_initiate_read(struct nfs_pgio_header *hdr,
 190                              struct rpc_message *msg,
 191                              const struct nfs_rpc_ops *rpc_ops,
 192                              struct rpc_task_setup *task_setup_data, int how)
 193{
 194        struct inode *inode = hdr->inode;
 195        int swap_flags = IS_SWAPFILE(inode) ? NFS_RPC_SWAPFLAGS : 0;
 196
 197        task_setup_data->flags |= swap_flags;
 198        rpc_ops->read_setup(hdr, msg);
 199}
 200
 201static void
 202nfs_async_read_error(struct list_head *head)
 203{
 204        struct nfs_page *req;
 205
 206        while (!list_empty(head)) {
 207                req = nfs_list_entry(head->next);
 208                nfs_list_remove_request(req);
 209                nfs_readpage_release(req);
 210        }
 211}
 212
 213static const struct nfs_pgio_completion_ops nfs_async_read_completion_ops = {
 214        .error_cleanup = nfs_async_read_error,
 215        .completion = nfs_read_completion,
 216};
 217
 218/*
 219 * This is the callback from RPC telling us whether a reply was
 220 * received or some error occurred (timeout or socket shutdown).
 221 */
 222static int nfs_readpage_done(struct rpc_task *task,
 223                             struct nfs_pgio_header *hdr,
 224                             struct inode *inode)
 225{
 226        int status = NFS_PROTO(inode)->read_done(task, hdr);
 227        if (status != 0)
 228                return status;
 229
 230        nfs_add_stats(inode, NFSIOS_SERVERREADBYTES, hdr->res.count);
 231
 232        if (task->tk_status == -ESTALE) {
 233                set_bit(NFS_INO_STALE, &NFS_I(inode)->flags);
 234                nfs_mark_for_revalidate(inode);
 235        }
 236        return 0;
 237}
 238
 239static void nfs_readpage_retry(struct rpc_task *task,
 240                               struct nfs_pgio_header *hdr)
 241{
 242        struct nfs_pgio_args *argp = &hdr->args;
 243        struct nfs_pgio_res  *resp = &hdr->res;
 244
 245        /* This is a short read! */
 246        nfs_inc_stats(hdr->inode, NFSIOS_SHORTREAD);
 247        /* Has the server at least made some progress? */
 248        if (resp->count == 0) {
 249                nfs_set_pgio_error(hdr, -EIO, argp->offset);
 250                return;
 251        }
 252
 253        /* For non rpc-based layout drivers, retry-through-MDS */
 254        if (!task->tk_ops) {
 255                hdr->pnfs_error = -EAGAIN;
 256                return;
 257        }
 258
 259        /* Yes, so retry the read at the end of the hdr */
 260        hdr->mds_offset += resp->count;
 261        argp->offset += resp->count;
 262        argp->pgbase += resp->count;
 263        argp->count -= resp->count;
 264        rpc_restart_call_prepare(task);
 265}
 266
 267static void nfs_readpage_result(struct rpc_task *task,
 268                                struct nfs_pgio_header *hdr)
 269{
 270        if (hdr->res.eof) {
 271                loff_t bound;
 272
 273                bound = hdr->args.offset + hdr->res.count;
 274                spin_lock(&hdr->lock);
 275                if (bound < hdr->io_start + hdr->good_bytes) {
 276                        set_bit(NFS_IOHDR_EOF, &hdr->flags);
 277                        clear_bit(NFS_IOHDR_ERROR, &hdr->flags);
 278                        hdr->good_bytes = bound - hdr->io_start;
 279                }
 280                spin_unlock(&hdr->lock);
 281        } else if (hdr->res.count < hdr->args.count)
 282                nfs_readpage_retry(task, hdr);
 283}
 284
 285/*
 286 * Read a page over NFS.
 287 * We read the page synchronously in the following case:
 288 *  -   The error flag is set for this page. This happens only when a
 289 *      previous async read operation failed.
 290 */
 291int nfs_readpage(struct file *file, struct page *page)
 292{
 293        struct nfs_open_context *ctx;
 294        struct inode *inode = page_file_mapping(page)->host;
 295        int             error;
 296
 297        dprintk("NFS: nfs_readpage (%p %ld@%lu)\n",
 298                page, PAGE_SIZE, page_index(page));
 299        nfs_inc_stats(inode, NFSIOS_VFSREADPAGE);
 300        nfs_add_stats(inode, NFSIOS_READPAGES, 1);
 301
 302        /*
 303         * Try to flush any pending writes to the file..
 304         *
 305         * NOTE! Because we own the page lock, there cannot
 306         * be any new pending writes generated at this point
 307         * for this page (other pages can be written to).
 308         */
 309        error = nfs_wb_page(inode, page);
 310        if (error)
 311                goto out_unlock;
 312        if (PageUptodate(page))
 313                goto out_unlock;
 314
 315        error = -ESTALE;
 316        if (NFS_STALE(inode))
 317                goto out_unlock;
 318
 319        if (file == NULL) {
 320                error = -EBADF;
 321                ctx = nfs_find_open_context(inode, NULL, FMODE_READ);
 322                if (ctx == NULL)
 323                        goto out_unlock;
 324        } else
 325                ctx = get_nfs_open_context(nfs_file_open_context(file));
 326
 327        if (!IS_SYNC(inode)) {
 328                error = nfs_readpage_from_fscache(ctx, inode, page);
 329                if (error == 0)
 330                        goto out;
 331        }
 332
 333        error = nfs_readpage_async(ctx, inode, page);
 334
 335out:
 336        put_nfs_open_context(ctx);
 337        return error;
 338out_unlock:
 339        unlock_page(page);
 340        return error;
 341}
 342
 343struct nfs_readdesc {
 344        struct nfs_pageio_descriptor *pgio;
 345        struct nfs_open_context *ctx;
 346};
 347
 348static int
 349readpage_async_filler(void *data, struct page *page)
 350{
 351        struct nfs_readdesc *desc = (struct nfs_readdesc *)data;
 352        struct nfs_page *new;
 353        unsigned int len;
 354        int error;
 355
 356        len = nfs_page_length(page);
 357        if (len == 0)
 358                return nfs_return_empty_page(page);
 359
 360        new = nfs_create_request(desc->ctx, page, NULL, 0, len);
 361        if (IS_ERR(new))
 362                goto out_error;
 363
 364        if (len < PAGE_SIZE)
 365                zero_user_segment(page, len, PAGE_SIZE);
 366        if (!nfs_pageio_add_request(desc->pgio, new)) {
 367                nfs_list_remove_request(new);
 368                nfs_readpage_release(new);
 369                error = desc->pgio->pg_error;
 370                goto out;
 371        }
 372        return 0;
 373out_error:
 374        error = PTR_ERR(new);
 375        unlock_page(page);
 376out:
 377        return error;
 378}
 379
 380int nfs_readpages(struct file *filp, struct address_space *mapping,
 381                struct list_head *pages, unsigned nr_pages)
 382{
 383        struct nfs_pageio_descriptor pgio;
 384        struct nfs_pgio_mirror *pgm;
 385        struct nfs_readdesc desc = {
 386                .pgio = &pgio,
 387        };
 388        struct inode *inode = mapping->host;
 389        unsigned long npages;
 390        int ret = -ESTALE;
 391
 392        dprintk("NFS: nfs_readpages (%s/%Lu %d)\n",
 393                        inode->i_sb->s_id,
 394                        (unsigned long long)NFS_FILEID(inode),
 395                        nr_pages);
 396        nfs_inc_stats(inode, NFSIOS_VFSREADPAGES);
 397
 398        if (NFS_STALE(inode))
 399                goto out;
 400
 401        if (filp == NULL) {
 402                desc.ctx = nfs_find_open_context(inode, NULL, FMODE_READ);
 403                if (desc.ctx == NULL)
 404                        return -EBADF;
 405        } else
 406                desc.ctx = get_nfs_open_context(nfs_file_open_context(filp));
 407
 408        /* attempt to read as many of the pages as possible from the cache
 409         * - this returns -ENOBUFS immediately if the cookie is negative
 410         */
 411        ret = nfs_readpages_from_fscache(desc.ctx, inode, mapping,
 412                                         pages, &nr_pages);
 413        if (ret == 0)
 414                goto read_complete; /* all pages were read */
 415
 416        nfs_pageio_init_read(&pgio, inode, false,
 417                             &nfs_async_read_completion_ops);
 418
 419        ret = read_cache_pages(mapping, pages, readpage_async_filler, &desc);
 420        nfs_pageio_complete(&pgio);
 421
 422        /* It doesn't make sense to do mirrored reads! */
 423        WARN_ON_ONCE(pgio.pg_mirror_count != 1);
 424
 425        pgm = &pgio.pg_mirrors[0];
 426        NFS_I(inode)->read_io += pgm->pg_bytes_written;
 427        npages = (pgm->pg_bytes_written + PAGE_SIZE - 1) >>
 428                 PAGE_SHIFT;
 429        nfs_add_stats(inode, NFSIOS_READPAGES, npages);
 430read_complete:
 431        put_nfs_open_context(desc.ctx);
 432out:
 433        return ret;
 434}
 435
 436int __init nfs_init_readpagecache(void)
 437{
 438        nfs_rdata_cachep = kmem_cache_create("nfs_read_data",
 439                                             sizeof(struct nfs_pgio_header),
 440                                             0, SLAB_HWCACHE_ALIGN,
 441                                             NULL);
 442        if (nfs_rdata_cachep == NULL)
 443                return -ENOMEM;
 444
 445        return 0;
 446}
 447
 448void nfs_destroy_readpagecache(void)
 449{
 450        kmem_cache_destroy(nfs_rdata_cachep);
 451}
 452
 453static const struct nfs_rw_ops nfs_rw_read_ops = {
 454        .rw_mode                = FMODE_READ,
 455        .rw_alloc_header        = nfs_readhdr_alloc,
 456        .rw_free_header         = nfs_readhdr_free,
 457        .rw_done                = nfs_readpage_done,
 458        .rw_result              = nfs_readpage_result,
 459        .rw_initiate            = nfs_initiate_read,
 460};
 461