cregit-Linux how code gets into the kernel

Release 4.11 fs/cachefiles/rdwr.c

Directory: fs/cachefiles
/* Storage object read/write
 *
 * Copyright (C) 2007 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 <linux/mount.h>
#include <linux/slab.h>
#include <linux/file.h>
#include <linux/swap.h>
#include "internal.h"

/*
 * detect wake up events generated by the unlocking of pages in which we're
 * interested
 * - we use this to detect read completion of backing pages
 * - the caller holds the waitqueue lock
 */

static int cachefiles_read_waiter(wait_queue_t *wait, unsigned mode, int sync, void *_key) { struct cachefiles_one_read *monitor = container_of(wait, struct cachefiles_one_read, monitor); struct cachefiles_object *object; struct wait_bit_key *key = _key; struct page *page = wait->private; ASSERT(key); _enter("{%lu},%u,%d,{%p,%u}", monitor->netfs_page->index, mode, sync, key->flags, key->bit_nr); if (key->flags != &page->flags || key->bit_nr != PG_locked) return 0; _debug("--- monitor %p %lx ---", page, page->flags); if (!PageUptodate(page) && !PageError(page)) { /* unlocked, not uptodate and not erronous? */ _debug("page probably truncated"); } /* remove from the waitqueue */ list_del(&wait->task_list); /* move onto the action list and queue for FS-Cache thread pool */ ASSERT(monitor->op); object = container_of(monitor->op->op.object, struct cachefiles_object, fscache); spin_lock(&object->work_lock); list_add_tail(&monitor->op_link, &monitor->op->to_do); spin_unlock(&object->work_lock); fscache_enqueue_retrieval(monitor->op); return 0; }

Contributors

PersonTokensPropCommitsCommitProp
David Howells213100.00%2100.00%
Total213100.00%2100.00%

/* * handle a probably truncated page * - check to see if the page is still relevant and reissue the read if * possible * - return -EIO on error, -ENODATA if the page is gone, -EINPROGRESS if we * must wait again and 0 if successful */
static int cachefiles_read_reissue(struct cachefiles_object *object, struct cachefiles_one_read *monitor) { struct address_space *bmapping = d_backing_inode(object->backer)->i_mapping; struct page *backpage = monitor->back_page, *backpage2; int ret; _enter("{ino=%lx},{%lx,%lx}", d_backing_inode(object->backer)->i_ino, backpage->index, backpage->flags); /* skip if the page was truncated away completely */ if (backpage->mapping != bmapping) { _leave(" = -ENODATA [mapping]"); return -ENODATA; } backpage2 = find_get_page(bmapping, backpage->index); if (!backpage2) { _leave(" = -ENODATA [gone]"); return -ENODATA; } if (backpage != backpage2) { put_page(backpage2); _leave(" = -ENODATA [different]"); return -ENODATA; } /* the page is still there and we already have a ref on it, so we don't * need a second */ put_page(backpage2); INIT_LIST_HEAD(&monitor->op_link); add_page_wait_queue(backpage, &monitor->monitor); if (trylock_page(backpage)) { ret = -EIO; if (PageError(backpage)) goto unlock_discard; ret = 0; if (PageUptodate(backpage)) goto unlock_discard; _debug("reissue read"); ret = bmapping->a_ops->readpage(NULL, backpage); if (ret < 0) goto unlock_discard; } /* but the page may have been read before the monitor was installed, so * the monitor may miss the event - so we have to ensure that we do get * one in such a case */ if (trylock_page(backpage)) { _debug("jumpstart %p {%lx}", backpage, backpage->flags); unlock_page(backpage); } /* it'll reappear on the todo list */ _leave(" = -EINPROGRESS"); return -EINPROGRESS; unlock_discard: unlock_page(backpage); spin_lock_irq(&object->work_lock); list_del(&monitor->op_link); spin_unlock_irq(&object->work_lock); _leave(" = %d", ret); return ret; }

Contributors

PersonTokensPropCommitsCommitProp
David Howells302100.00%3100.00%
Total302100.00%3100.00%

/* * copy data from backing pages to netfs pages to complete a read operation * - driven by FS-Cache's thread pool */
static void cachefiles_read_copier(struct fscache_operation *_op) { struct cachefiles_one_read *monitor; struct cachefiles_object *object; struct fscache_retrieval *op; int error, max; op = container_of(_op, struct fscache_retrieval, op); object = container_of(op->op.object, struct cachefiles_object, fscache); _enter("{ino=%lu}", d_backing_inode(object->backer)->i_ino); max = 8; spin_lock_irq(&object->work_lock); while (!list_empty(&op->to_do)) { monitor = list_entry(op->to_do.next, struct cachefiles_one_read, op_link); list_del(&monitor->op_link); spin_unlock_irq(&object->work_lock); _debug("- copy {%lu}", monitor->back_page->index); recheck: if (test_bit(FSCACHE_COOKIE_INVALIDATING, &object->fscache.cookie->flags)) { error = -ESTALE; } else if (PageUptodate(monitor->back_page)) { copy_highpage(monitor->netfs_page, monitor->back_page); fscache_mark_page_cached(monitor->op, monitor->netfs_page); error = 0; } else if (!PageError(monitor->back_page)) { /* the page has probably been truncated */ error = cachefiles_read_reissue(object, monitor); if (error == -EINPROGRESS) goto next; goto recheck; } else { cachefiles_io_error_obj( object, "Readpage failed on backing file %lx", (unsigned long) monitor->back_page->flags); error = -EIO; } put_page(monitor->back_page); fscache_end_io(op, monitor->netfs_page, error); put_page(monitor->netfs_page); fscache_retrieval_complete(op, 1); fscache_put_retrieval(op); kfree(monitor); next: /* let the thread pool have some air occasionally */ max--; if (max < 0 || need_resched()) { if (!list_empty(&op->to_do)) fscache_enqueue_retrieval(op); _leave(" [maxed out]"); return; } spin_lock_irq(&object->work_lock); } spin_unlock_irq(&object->work_lock); _leave(""); }

Contributors

PersonTokensPropCommitsCommitProp
David Howells36599.46%685.71%
Kirill A. Shutemov20.54%114.29%
Total367100.00%7100.00%

/* * read the corresponding page to the given set from the backing file * - an uncertain page is simply discarded, to be tried again another time */
static int cachefiles_read_backing_file_one(struct cachefiles_object *object, struct fscache_retrieval *op, struct page *netpage) { struct cachefiles_one_read *monitor; struct address_space *bmapping; struct page *newpage, *backpage; int ret; _enter(""); _debug("read back %p{%lu,%d}", netpage, netpage->index, page_count(netpage)); monitor = kzalloc(sizeof(*monitor), cachefiles_gfp); if (!monitor) goto nomem; monitor->netfs_page = netpage; monitor->op = fscache_get_retrieval(op); init_waitqueue_func_entry(&monitor->monitor, cachefiles_read_waiter); /* attempt to get hold of the backing page */ bmapping = d_backing_inode(object->backer)->i_mapping; newpage = NULL; for (;;) { backpage = find_get_page(bmapping, netpage->index); if (backpage) goto backing_page_already_present; if (!newpage) { newpage = __page_cache_alloc(cachefiles_gfp | __GFP_COLD); if (!newpage) goto nomem_monitor; } ret = add_to_page_cache_lru(newpage, bmapping, netpage->index, cachefiles_gfp); if (ret == 0) goto installed_new_backing_page; if (ret != -EEXIST) goto nomem_page; } /* we've installed a new backing page, so now we need to start * it reading */ installed_new_backing_page: _debug("- new %p", newpage); backpage = newpage; newpage = NULL; read_backing_page: ret = bmapping->a_ops->readpage(NULL, backpage); if (ret < 0) goto read_error; /* set the monitor to transfer the data across */ monitor_backing_page: _debug("- monitor add"); /* install the monitor */ get_page(monitor->netfs_page); get_page(backpage); monitor->back_page = backpage; monitor->monitor.private = backpage; add_page_wait_queue(backpage, &monitor->monitor); monitor = NULL; /* but the page may have been read before the monitor was installed, so * the monitor may miss the event - so we have to ensure that we do get * one in such a case */ if (trylock_page(backpage)) { _debug("jumpstart %p {%lx}", backpage, backpage->flags); unlock_page(backpage); } goto success; /* if the backing page is already present, it can be in one of * three states: read in progress, read failed or read okay */ backing_page_already_present: _debug("- present"); if (newpage) { put_page(newpage); newpage = NULL; } if (PageError(backpage)) goto io_error; if (PageUptodate(backpage)) goto backing_page_already_uptodate; if (!trylock_page(backpage)) goto monitor_backing_page; _debug("read %p {%lx}", backpage, backpage->flags); goto read_backing_page; /* the backing page is already up to date, attach the netfs * page to the pagecache and LRU and copy the data across */ backing_page_already_uptodate: _debug("- uptodate"); fscache_mark_page_cached(op, netpage); copy_highpage(netpage, backpage); fscache_end_io(op, netpage, 0); fscache_retrieval_complete(op, 1); success: _debug("success"); ret = 0; out: if (backpage) put_page(backpage); if (monitor) { fscache_put_retrieval(monitor->op); kfree(monitor); } _leave(" = %d", ret); return ret; read_error: _debug("read error %d", ret); if (ret == -ENOMEM) { fscache_retrieval_complete(op, 1); goto out; } io_error: cachefiles_io_error_obj(object, "Page read error on backing file"); fscache_retrieval_complete(op, 1); ret = -ENOBUFS; goto out; nomem_page: put_page(newpage); nomem_monitor: fscache_put_retrieval(monitor->op); kfree(monitor); nomem: fscache_retrieval_complete(op, 1); _leave(" = -ENOMEM"); return -ENOMEM; }

Contributors

PersonTokensPropCommitsCommitProp
David Howells56898.78%675.00%
Kirill A. Shutemov50.87%112.50%
Johannes Weiner20.35%112.50%
Total575100.00%8100.00%

/* * read a page from the cache or allocate a block in which to store it * - cache withdrawal is prevented by the caller * - returns -EINTR if interrupted * - returns -ENOMEM if ran out of memory * - returns -ENOBUFS if no buffers can be made available * - returns -ENOBUFS if page is beyond EOF * - if the page is backed by a block in the cache: * - a read will be started which will call the callback on completion * - 0 will be returned * - else if the page is unbacked: * - the metadata will be retained * - -ENODATA will be returned */
int cachefiles_read_or_alloc_page(struct fscache_retrieval *op, struct page *page, gfp_t gfp) { struct cachefiles_object *object; struct cachefiles_cache *cache; struct inode *inode; sector_t block0, block; unsigned shift; int ret; object = container_of(op->op.object, struct cachefiles_object, fscache); cache = container_of(object->fscache.cache, struct cachefiles_cache, cache); _enter("{%p},{%lx},,,", object, page->index); if (!object->backer) goto enobufs; inode = d_backing_inode(object->backer); ASSERT(S_ISREG(inode->i_mode)); ASSERT(inode->i_mapping->a_ops->bmap); ASSERT(inode->i_mapping->a_ops->readpages); /* calculate the shift required to use bmap */ shift = PAGE_SHIFT - inode->i_sb->s_blocksize_bits; op->op.flags &= FSCACHE_OP_KEEP_FLAGS; op->op.flags |= FSCACHE_OP_ASYNC; op->op.processor = cachefiles_read_copier; /* we assume the absence or presence of the first block is a good * enough indication for the page as a whole * - TODO: don't use bmap() for this as it is _not_ actually good * enough for this as it doesn't indicate errors, but it's all we've * got for the moment */ block0 = page->index; block0 <<= shift; block = inode->i_mapping->a_ops->bmap(inode->i_mapping, block0); _debug("%llx -> %llx", (unsigned long long) block0, (unsigned long long) block); if (block) { /* submit the apparently valid page to the backing fs to be * read from disk */ ret = cachefiles_read_backing_file_one(object, op, page); } else if (cachefiles_has_space(cache, 0, 1) == 0) { /* there's space in the cache we can use */ fscache_mark_page_cached(op, page); fscache_retrieval_complete(op, 1); ret = -ENODATA; } else { goto enobufs; } _leave(" = %d", ret); return ret; enobufs: fscache_retrieval_complete(op, 1); _leave(" = -ENOBUFS"); return -ENOBUFS; }

Contributors

PersonTokensPropCommitsCommitProp
David Howells30799.68%583.33%
Tejun Heo10.32%116.67%
Total308100.00%6100.00%

/* * read the corresponding pages to the given set from the backing file * - any uncertain pages are simply discarded, to be tried again another time */
static int cachefiles_read_backing_file(struct cachefiles_object *object, struct fscache_retrieval *op, struct list_head *list) { struct cachefiles_one_read *monitor = NULL; struct address_space *bmapping = d_backing_inode(object->backer)->i_mapping; struct page *newpage = NULL, *netpage, *_n, *backpage = NULL; int ret = 0; _enter(""); list_for_each_entry_safe(netpage, _n, list, lru) { list_del(&netpage->lru); _debug("read back %p{%lu,%d}", netpage, netpage->index, page_count(netpage)); if (!monitor) { monitor = kzalloc(sizeof(*monitor), cachefiles_gfp); if (!monitor) goto nomem; monitor->op = fscache_get_retrieval(op); init_waitqueue_func_entry(&monitor->monitor, cachefiles_read_waiter); } for (;;) { backpage = find_get_page(bmapping, netpage->index); if (backpage) goto backing_page_already_present; if (!newpage) { newpage = __page_cache_alloc(cachefiles_gfp | __GFP_COLD); if (!newpage) goto nomem; } ret = add_to_page_cache_lru(newpage, bmapping, netpage->index, cachefiles_gfp); if (ret == 0) goto installed_new_backing_page; if (ret != -EEXIST) goto nomem; } /* we've installed a new backing page, so now we need * to start it reading */ installed_new_backing_page: _debug("- new %p", newpage); backpage = newpage; newpage = NULL; reread_backing_page: ret = bmapping->a_ops->readpage(NULL, backpage); if (ret < 0) goto read_error; /* add the netfs page to the pagecache and LRU, and set the * monitor to transfer the data across */ monitor_backing_page: _debug("- monitor add"); ret = add_to_page_cache_lru(netpage, op->mapping, netpage->index, cachefiles_gfp); if (ret < 0) { if (ret == -EEXIST) { put_page(netpage); fscache_retrieval_complete(op, 1); continue; } goto nomem; } /* install a monitor */ get_page(netpage); monitor->netfs_page = netpage; get_page(backpage); monitor->back_page = backpage; monitor->monitor.private = backpage; add_page_wait_queue(backpage, &monitor->monitor); monitor = NULL; /* but the page may have been read before the monitor was * installed, so the monitor may miss the event - so we have to * ensure that we do get one in such a case */ if (trylock_page(backpage)) { _debug("2unlock %p {%lx}", backpage, backpage->flags); unlock_page(backpage); } put_page(backpage); backpage = NULL; put_page(netpage); netpage = NULL; continue; /* if the backing page is already present, it can be in one of * three states: read in progress, read failed or read okay */ backing_page_already_present: _debug("- present %p", backpage); if (PageError(backpage)) goto io_error; if (PageUptodate(backpage)) goto backing_page_already_uptodate; _debug("- not ready %p{%lx}", backpage, backpage->flags); if (!trylock_page(backpage)) goto monitor_backing_page; if (PageError(backpage)) { _debug("error %lx", backpage->flags); unlock_page(backpage); goto io_error; } if (PageUptodate(backpage)) goto backing_page_already_uptodate_unlock; /* we've locked a page that's neither up to date nor erroneous, * so we need to attempt to read it again */ goto reread_backing_page; /* the backing page is already up to date, attach the netfs * page to the pagecache and LRU and copy the data across */ backing_page_already_uptodate_unlock: _debug("uptodate %lx", backpage->flags); unlock_page(backpage); backing_page_already_uptodate: _debug("- uptodate"); ret = add_to_page_cache_lru(netpage, op->mapping, netpage->index, cachefiles_gfp); if (ret < 0) { if (ret == -EEXIST) { put_page(netpage); fscache_retrieval_complete(op, 1); continue; } goto nomem; } copy_highpage(netpage, backpage); put_page(backpage); backpage = NULL; fscache_mark_page_cached(op, netpage); /* the netpage is unlocked and marked up to date here */ fscache_end_io(op, netpage, 0); put_page(netpage); netpage = NULL; fscache_retrieval_complete(op, 1); continue; } netpage = NULL; _debug("out"); out: /* tidy up */ if (newpage) put_page(newpage); if (netpage) put_page(netpage); if (backpage) put_page(backpage); if (monitor) { fscache_put_retrieval(op); kfree(monitor); } list_for_each_entry_safe(netpage, _n, list, lru) { list_del(&netpage->lru); put_page(netpage); fscache_retrieval_complete(op, 1); } _leave(" = %d", ret); return ret; nomem: _debug("nomem"); ret = -ENOMEM; goto record_page_complete; read_error: _debug("read error %d", ret); if (ret == -ENOMEM) goto record_page_complete; io_error: cachefiles_io_error_obj(object, "Page read error on backing file"); ret = -ENOBUFS; record_page_complete: fscache_retrieval_complete(op, 1); goto out; }

Contributors

PersonTokensPropCommitsCommitProp
David Howells78398.00%675.00%
Kirill A. Shutemov121.50%112.50%
Johannes Weiner40.50%112.50%
Total799100.00%8100.00%

/* * read a list of pages from the cache or allocate blocks in which to store * them */
int cachefiles_read_or_alloc_pages(struct fscache_retrieval *op, struct list_head *pages, unsigned *nr_pages, gfp_t gfp) { struct cachefiles_object *object; struct cachefiles_cache *cache; struct list_head backpages; struct pagevec pagevec; struct inode *inode; struct page *page, *_n; unsigned shift, nrbackpages; int ret, ret2, space; object = container_of(op->op.object, struct cachefiles_object, fscache); cache = container_of(object->fscache.cache, struct cachefiles_cache, cache); _enter("{OBJ%x,%d},,%d,,", object->fscache.debug_id, atomic_read(&op->op.usage), *nr_pages); if (!object->backer) goto all_enobufs; space = 1; if (cachefiles_has_space(cache, 0, *nr_pages) < 0) space = 0; inode = d_backing_inode(object->backer); ASSERT(S_ISREG(inode->i_mode)); ASSERT(inode->i_mapping->a_ops->bmap); ASSERT(inode->i_mapping->a_ops->readpages); /* calculate the shift required to use bmap */ shift = PAGE_SHIFT - inode->i_sb->s_blocksize_bits; pagevec_init(&pagevec, 0); op->op.flags &= FSCACHE_OP_KEEP_FLAGS; op->op.flags |= FSCACHE_OP_ASYNC; op->op.processor = cachefiles_read_copier; INIT_LIST_HEAD(&backpages); nrbackpages = 0; ret = space ? -ENODATA : -ENOBUFS; list_for_each_entry_safe(page, _n, pages, lru) { sector_t block0, block; /* we assume the absence or presence of the first block is a * good enough indication for the page as a whole * - TODO: don't use bmap() for this as it is _not_ actually * good enough for this as it doesn't indicate errors, but * it's all we've got for the moment */ block0 = page->index; block0 <<= shift; block = inode->i_mapping->a_ops->bmap(inode->i_mapping, block0); _debug("%llx -> %llx", (unsigned long long) block0, (unsigned long long) block); if (block) { /* we have data - add it to the list to give to the * backing fs */ list_move(&page->lru, &backpages); (*nr_pages)--; nrbackpages++; } else if (space && pagevec_add(&pagevec, page) == 0) { fscache_mark_pages_cached(op, &pagevec); fscache_retrieval_complete(op, 1); ret = -ENODATA; } else { fscache_retrieval_complete(op