diff options
Diffstat (limited to 'mm/filemap.c')
| -rw-r--r-- | mm/filemap.c | 46 |
1 files changed, 33 insertions, 13 deletions
diff --git a/mm/filemap.c b/mm/filemap.c index 93595c327bbd..d5fdae2eb183 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -123,8 +123,7 @@ void remove_from_page_cache(struct page *page) { struct address_space *mapping = page->mapping; - if (unlikely(!PageLocked(page))) - PAGE_BUG(page); + BUG_ON(!PageLocked(page)); write_lock_irq(&mapping->tree_lock); __remove_from_page_cache(page); @@ -139,7 +138,25 @@ static int sync_page(void *word) page = container_of((page_flags_t *)word, struct page, flags); /* - * FIXME, fercrissake. What is this barrier here for? + * page_mapping() is being called without PG_locked held. + * Some knowledge of the state and use of the page is used to + * reduce the requirements down to a memory barrier. + * The danger here is of a stale page_mapping() return value + * indicating a struct address_space different from the one it's + * associated with when it is associated with one. + * After smp_mb(), it's either the correct page_mapping() for + * the page, or an old page_mapping() and the page's own + * page_mapping() has gone NULL. + * The ->sync_page() address_space operation must tolerate + * page_mapping() going NULL. By an amazing coincidence, + * this comes about because none of the users of the page + * in the ->sync_page() methods make essential use of the + * page_mapping(), merely passing the page down to the backing + * device's unplug functions when it's non-NULL, which in turn + * ignore it for all cases but swap, where only page->private is + * of interest. When page_mapping() does go NULL, the entire + * call stack gracefully ignores the page and returns. + * -- wli */ smp_mb(); mapping = page_mapping(page); @@ -152,9 +169,10 @@ static int sync_page(void *word) /** * filemap_fdatawrite_range - start writeback against all of a mapping's * dirty pages that lie within the byte offsets <start, end> - * @mapping: address space structure to write - * @start: offset in bytes where the range starts - * @end : offset in bytes where the range ends + * @mapping: address space structure to write + * @start: offset in bytes where the range starts + * @end: offset in bytes where the range ends + * @sync_mode: enable synchronous operation * * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as * opposed to a regular memory * cleansing writeback. The difference between @@ -518,8 +536,8 @@ EXPORT_SYMBOL(find_trylock_page); /** * find_lock_page - locate, pin and lock a pagecache page * - * @mapping - the address_space to search - * @offset - the page index + * @mapping: the address_space to search + * @offset: the page index * * Locates the desired pagecache page, locks it, increments its reference * count and returns its address. @@ -558,9 +576,9 @@ EXPORT_SYMBOL(find_lock_page); /** * find_or_create_page - locate or add a pagecache page * - * @mapping - the page's address_space - * @index - the page's index into the mapping - * @gfp_mask - page allocation mode + * @mapping: the page's address_space + * @index: the page's index into the mapping + * @gfp_mask: page allocation mode * * Locates a page in the pagecache. If the page is not present, a new page * is allocated using @gfp_mask and is added to the pagecache and to the VM's @@ -1949,7 +1967,7 @@ generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov, buf = iov->iov_base + written; else { filemap_set_next_iovec(&cur_iov, &iov_base, written); - buf = iov->iov_base + iov_base; + buf = cur_iov->iov_base + iov_base; } do { @@ -2007,9 +2025,11 @@ generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov, count -= status; pos += status; buf += status; - if (unlikely(nr_segs > 1)) + if (unlikely(nr_segs > 1)) { filemap_set_next_iovec(&cur_iov, &iov_base, status); + buf = cur_iov->iov_base + iov_base; + } } } if (unlikely(copied != bytes)) |