diff options
| -rw-r--r-- | fs/cachefiles/rdwr.c | 99 |
1 files changed, 93 insertions, 6 deletions
diff --git a/fs/cachefiles/rdwr.c b/fs/cachefiles/rdwr.c index 5a84fd7..1d83325 100644 --- a/fs/cachefiles/rdwr.c +++ b/fs/cachefiles/rdwr.c @@ -40,8 +40,10 @@ static int cachefiles_read_waiter(wait_queue_t *wait, unsigned mode, _debug("--- monitor %p %lx ---", page, page->flags); - if (!PageUptodate(page) && !PageError(page)) - dump_stack(); + if (!PageUptodate(page) && !PageError(page)) { + /* unlocked, not uptodate and not erronous? */ + _debug("page probably truncated"); + } /* remove from the waitqueue */ list_del(&wait->task_list); @@ -61,6 +63,84 @@ static int cachefiles_read_waiter(wait_queue_t *wait, unsigned mode, } /* + * 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 = object->backer->d_inode->i_mapping; + struct page *backpage = monitor->back_page, *backpage2; + int ret; + + kenter("{ino=%lx},{%lx,%lx}", + object->backer->d_inode->i_ino, + backpage->index, backpage->flags); + + /* skip if the page was truncated away completely */ + if (backpage->mapping != bmapping) { + kleave(" = -ENODATA [mapping]"); + return -ENODATA; + } + + backpage2 = find_get_page(bmapping, backpage->index); + if (!backpage2) { + kleave(" = -ENODATA [gone]"); + return -ENODATA; + } + + if (backpage != backpage2) { + put_page(backpage2); + kleave(" = -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; + + kdebug("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 */ + kleave(" = -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); + kleave(" = %d", ret); + return ret; +} + +/* * copy data from backing pages to netfs pages to complete a read operation * - driven by FS-Cache's thread pool */ @@ -92,20 +172,26 @@ static void cachefiles_read_copier(struct fscache_operation *_op) _debug("- copy {%lu}", monitor->back_page->index); - error = -EIO; + recheck: if (PageUptodate(monitor->back_page)) { copy_highpage(monitor->netfs_page, monitor->back_page); pagevec_add(&pagevec, monitor->netfs_page); fscache_mark_pages_cached(monitor->op, &pagevec); error = 0; - } - - if (error) + } 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; + } page_cache_release(monitor->back_page); @@ -114,6 +200,7 @@ static void cachefiles_read_copier(struct fscache_operation *_op) fscache_put_retrieval(op); kfree(monitor); + next: /* let the thread pool have some air occasionally */ max--; if (max < 0 || need_resched()) { |
