diff options
Diffstat (limited to 'fs/cachefiles/rdwr.c')
| -rw-r--r-- | fs/cachefiles/rdwr.c | 978 |
1 files changed, 978 insertions, 0 deletions
diff --git a/fs/cachefiles/rdwr.c b/fs/cachefiles/rdwr.c new file mode 100644 index 000000000..f5bf10729 --- /dev/null +++ b/fs/cachefiles/rdwr.c @@ -0,0 +1,978 @@ +/* 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_entry_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 fscache_retrieval *op = monitor->op; + 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->entry); + + /* move onto the action list and queue for FS-Cache thread pool */ + ASSERT(op); + + /* We need to temporarily bump the usage count as we don't own a ref + * here otherwise cachefiles_read_copier() may free the op between the + * monitor being enqueued on the op->to_do list and the op getting + * enqueued on the work queue. + */ + fscache_get_retrieval(op); + + object = container_of(op->op.object, struct cachefiles_object, fscache); + spin_lock(&object->work_lock); + list_add_tail(&monitor->op_link, &op->to_do); + fscache_enqueue_retrieval(op); + spin_unlock(&object->work_lock); + + fscache_put_retrieval(op); + return 0; +} + +/* + * 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 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); +discard: + spin_lock_irq(&object->work_lock); + list_del(&monitor->op_link); + spin_unlock_irq(&object->work_lock); + _leave(" = %d", ret); + return ret; +} + +/* + * 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(""); +} + +/* + * 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); + 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; +} + +/* + * 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; +} + +/* + * 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); + 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(backpage); + backpage = NULL; + put_page(netpage); + netpage = NULL; + 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(backpage); + backpage = NULL; + put_page(netpage); + netpage = NULL; + 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; +} + +/* + * 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); + + 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, 1); + } + } + + if (pagevec_count(&pagevec) > 0) + fscache_mark_pages_cached(op, &pagevec); + + if (list_empty(pages)) + ret = 0; + + /* submit the apparently valid pages to the backing fs to be read from + * disk */ + if (nrbackpages > 0) { + ret2 = cachefiles_read_backing_file(object, op, &backpages); + if (ret2 == -ENOMEM || ret2 == -EINTR) + ret = ret2; + } + + _leave(" = %d [nr=%u%s]", + ret, *nr_pages, list_empty(pages) ? " empty" : ""); + return ret; + +all_enobufs: + fscache_retrieval_complete(op, *nr_pages); + return -ENOBUFS; +} + +/* + * allocate a block in the cache in which to store a page + * - 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 + * - otherwise: + * - the metadata will be retained + * - 0 will be returned + */ +int cachefiles_allocate_page(struct fscache_retrieval *op, + struct page *page, + gfp_t gfp) +{ + struct cachefiles_object *object; + struct cachefiles_cache *cache; + 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); + + ret = cachefiles_has_space(cache, 0, 1); + if (ret == 0) + fscache_mark_page_cached(op, page); + else + ret = -ENOBUFS; + + fscache_retrieval_complete(op, 1); + _leave(" = %d", ret); + return ret; +} + +/* + * allocate blocks in the cache in which to store a set of pages + * - cache withdrawal is prevented by the caller + * - returns -EINTR if interrupted + * - returns -ENOMEM if ran out of memory + * - returns -ENOBUFS if some buffers couldn't be made available + * - returns -ENOBUFS if some pages are beyond EOF + * - otherwise: + * - -ENODATA will be returned + * - metadata will be retained for any page marked + */ +int cachefiles_allocate_pages(struct fscache_retrieval *op, + struct list_head *pages, + unsigned *nr_pages, + gfp_t gfp) +{ + struct cachefiles_object *object; + struct cachefiles_cache *cache; + struct pagevec pagevec; + struct page *page; + int ret; + + object = container_of(op->op.object, + struct cachefiles_object, fscache); + cache = container_of(object->fscache.cache, + struct cachefiles_cache, cache); + + _enter("%p,,,%d,", object, *nr_pages); + + ret = cachefiles_has_space(cache, 0, *nr_pages); + if (ret == 0) { + pagevec_init(&pagevec); + + list_for_each_entry(page, pages, lru) { + if (pagevec_add(&pagevec, page) == 0) + fscache_mark_pages_cached(op, &pagevec); + } + + if (pagevec_count(&pagevec) > 0) + fscache_mark_pages_cached(op, &pagevec); + ret = -ENODATA; + } else { + ret = -ENOBUFS; + } + + fscache_retrieval_complete(op, *nr_pages); + _leave(" = %d", ret); + return ret; +} + +/* + * request a page be stored in the cache + * - cache withdrawal is prevented by the caller + * - this request may be ignored if there's no cache block available, in which + * case -ENOBUFS will be returned + * - if the op is in progress, 0 will be returned + */ +int cachefiles_write_page(struct fscache_storage *op, struct page *page) +{ + struct cachefiles_object *object; + struct cachefiles_cache *cache; + struct file *file; + struct path path; + loff_t pos, eof; + size_t len; + void *data; + int ret = -ENOBUFS; + + ASSERT(op != NULL); + ASSERT(page != NULL); + + object = container_of(op->op.object, + struct cachefiles_object, fscache); + + _enter("%p,%p{%lx},,,", object, page, page->index); + + if (!object->backer) { + _leave(" = -ENOBUFS"); + return -ENOBUFS; + } + + ASSERT(d_is_reg(object->backer)); + + cache = container_of(object->fscache.cache, + struct cachefiles_cache, cache); + + pos = (loff_t)page->index << PAGE_SHIFT; + + /* We mustn't write more data than we have, so we have to beware of a + * partial page at EOF. + */ + eof = object->fscache.store_limit_l; + if (pos >= eof) + goto error; + + /* write the page to the backing filesystem and let it store it in its + * own time */ + path.mnt = cache->mnt; + path.dentry = object->backer; + file = dentry_open(&path, O_RDWR | O_LARGEFILE, cache->cache_cred); + if (IS_ERR(file)) { + ret = PTR_ERR(file); + goto error_2; + } + + len = PAGE_SIZE; + if (eof & ~PAGE_MASK) { + if (eof - pos < PAGE_SIZE) { + _debug("cut short %llx to %llx", + pos, eof); + len = eof - pos; + ASSERTCMP(pos + len, ==, eof); + } + } + + data = kmap(page); + ret = __kernel_write(file, data, len, &pos); + kunmap(page); + fput(file); + if (ret != len) + goto error_eio; + + _leave(" = 0"); + return 0; + +error_eio: + ret = -EIO; +error_2: + if (ret == -EIO) + cachefiles_io_error_obj(object, + "Write page to backing file failed"); +error: + _leave(" = -ENOBUFS [%d]", ret); + return -ENOBUFS; +} + +/* + * detach a backing block from a page + * - cache withdrawal is prevented by the caller + */ +void cachefiles_uncache_page(struct fscache_object *_object, struct page *page) + __releases(&object->fscache.cookie->lock) +{ + struct cachefiles_object *object; + + object = container_of(_object, struct cachefiles_object, fscache); + + _enter("%p,{%lu}", object, page->index); + + spin_unlock(&object->fscache.cookie->lock); +} |