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Messages in this thread Complete thread (EXPERIMENTAL) |
Evgeniy Dushistov <dushistov@mail.ru> wrote: +struct page *ufs_get_locked_page(struct address_space *mapping,
+ pgoff_t index)
+{ + struct page *page; + +try_again: + page = find_lock_page(mapping, index); + if (!page) { + page = read_cache_page(mapping, index, + (filler_t*)mapping->a_ops->readpage, + NULL); + if (IS_ERR(page)) { + printk(KERN_ERR "ufs_change_blocknr: " + "read_cache_page error: ino %lu, index: %lu\n", + mapping->host->i_ino, index); + goto out; + } + + lock_page(page); + + if (!PageUptodate(page) || PageError(page)) { + unlock_page(page); + page_cache_release(page); + + printk(KERN_ERR "ufs_change_blocknr: " + "can not read page: ino %lu, index: %lu\n", + mapping->host->i_ino, index); + + page = ERR_PTR(-EIO); + goto out; + } + } + + if (unlikely(!page->mapping || !page_has_buffers(page))) { + unlock_page(page); + page_cache_release(page); + goto try_again;/*we really need these buffers*/ + } +out: + return page; +} I think there's a (preexisting) problem here. When one thread is executing ufs_get_locked_page() while a second thread is running truncate(). If truncate got to the page first, truncate_complete_page() will mark the page !uptodate and will later unlock it. Now this function gets the page lock and emits a printk (bad) and assumes -EIO (worse). That scenario might not be possible because of i_mutex coverage, dunno. But if it _is_ possible, it can be simply fixed by doing lock_page(page); + if (page->mapping == NULL) {
+ /* truncate() got there first */
+ page_cache_release(page);
+ goto try_again;
+ }
That's if it is appropriate to re-instantiate the page at a place which is
now outside i_size... | ||||||||||
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