From b85e0effd3dcbf9118b896232f59526ab1a39a74 Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Mon, 25 Jul 2011 17:12:25 -0700 Subject: mm: consistent truncate and invalidate loops Make the pagevec_lookup loops in truncate_inode_pages_range(), invalidate_mapping_pages() and invalidate_inode_pages2_range() more consistent with each other. They were relying upon page->index of an unlocked page, but apologizing for it: accept it, embrace it, add comments and WARN_ONs, and simplify the index handling. invalidate_inode_pages2_range() had special handling for a wrapped page->index + 1 = 0 case; but MAX_LFS_FILESIZE doesn't let us anywhere near there, and a corrupt page->index in the radix_tree could cause more trouble than that would catch. Remove that wrapped handling. invalidate_inode_pages2_range() uses min() to limit the pagevec_lookup when near the end of the range: copy that into the other two, although it's less useful than you might think (it limits the use of the buffer, rather than the indices looked up). Signed-off-by: Hugh Dickins Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/filemap.c | 2 ++ mm/truncate.c | 110 +++++++++++++++++++++++++--------------------------------- 2 files changed, 49 insertions(+), 63 deletions(-) (limited to 'mm') diff --git a/mm/filemap.c b/mm/filemap.c index 2780be4bd49..10a17111327 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -128,6 +128,7 @@ void __delete_from_page_cache(struct page *page) radix_tree_delete(&mapping->page_tree, page->index); page->mapping = NULL; + /* Leave page->index set: truncation lookup relies upon it */ mapping->nrpages--; __dec_zone_page_state(page, NR_FILE_PAGES); if (PageSwapBacked(page)) @@ -483,6 +484,7 @@ int add_to_page_cache_locked(struct page *page, struct address_space *mapping, spin_unlock_irq(&mapping->tree_lock); } else { page->mapping = NULL; + /* Leave page->index set: truncation relies upon it */ spin_unlock_irq(&mapping->tree_lock); mem_cgroup_uncharge_cache_page(page); page_cache_release(page); diff --git a/mm/truncate.c b/mm/truncate.c index c924764e2ce..dc459014f77 100644 --- a/mm/truncate.c +++ b/mm/truncate.c @@ -199,9 +199,6 @@ int invalidate_inode_page(struct page *page) * The first pass will remove most pages, so the search cost of the second pass * is low. * - * When looking at page->index outside the page lock we need to be careful to - * copy it into a local to avoid races (it could change at any time). - * * We pass down the cache-hot hint to the page freeing code. Even if the * mapping is large, it is probably the case that the final pages are the most * recently touched, and freeing happens in ascending file offset order. @@ -210,10 +207,10 @@ void truncate_inode_pages_range(struct address_space *mapping, loff_t lstart, loff_t lend) { const pgoff_t start = (lstart + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT; - pgoff_t end; const unsigned partial = lstart & (PAGE_CACHE_SIZE - 1); struct pagevec pvec; - pgoff_t next; + pgoff_t index; + pgoff_t end; int i; cleancache_flush_inode(mapping); @@ -224,24 +221,21 @@ void truncate_inode_pages_range(struct address_space *mapping, end = (lend >> PAGE_CACHE_SHIFT); pagevec_init(&pvec, 0); - next = start; - while (next <= end && - pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) { + index = start; + while (index <= end && pagevec_lookup(&pvec, mapping, index, + min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) { mem_cgroup_uncharge_start(); for (i = 0; i < pagevec_count(&pvec); i++) { struct page *page = pvec.pages[i]; - pgoff_t page_index = page->index; - if (page_index > end) { - next = page_index; + /* We rely upon deletion not changing page->index */ + index = page->index; + if (index > end) break; - } - if (page_index > next) - next = page_index; - next++; if (!trylock_page(page)) continue; + WARN_ON(page->index != index); if (PageWriteback(page)) { unlock_page(page); continue; @@ -252,6 +246,7 @@ void truncate_inode_pages_range(struct address_space *mapping, pagevec_release(&pvec); mem_cgroup_uncharge_end(); cond_resched(); + index++; } if (partial) { @@ -264,13 +259,14 @@ void truncate_inode_pages_range(struct address_space *mapping, } } - next = start; + index = start; for ( ; ; ) { cond_resched(); - if (!pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) { - if (next == start) + if (!pagevec_lookup(&pvec, mapping, index, + min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) { + if (index == start) break; - next = start; + index = start; continue; } if (pvec.pages[0]->index > end) { @@ -281,18 +277,20 @@ void truncate_inode_pages_range(struct address_space *mapping, for (i = 0; i < pagevec_count(&pvec); i++) { struct page *page = pvec.pages[i]; - if (page->index > end) + /* We rely upon deletion not changing page->index */ + index = page->index; + if (index > end) break; + lock_page(page); + WARN_ON(page->index != index); wait_on_page_writeback(page); truncate_inode_page(mapping, page); - if (page->index > next) - next = page->index; - next++; unlock_page(page); } pagevec_release(&pvec); mem_cgroup_uncharge_end(); + index++; } cleancache_flush_inode(mapping); } @@ -333,35 +331,26 @@ unsigned long invalidate_mapping_pages(struct address_space *mapping, pgoff_t start, pgoff_t end) { struct pagevec pvec; - pgoff_t next = start; + pgoff_t index = start; unsigned long ret; unsigned long count = 0; int i; pagevec_init(&pvec, 0); - while (next <= end && - pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) { + while (index <= end && pagevec_lookup(&pvec, mapping, index, + min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) { mem_cgroup_uncharge_start(); for (i = 0; i < pagevec_count(&pvec); i++) { struct page *page = pvec.pages[i]; - pgoff_t index; - int lock_failed; - - lock_failed = !trylock_page(page); - /* - * We really shouldn't be looking at the ->index of an - * unlocked page. But we're not allowed to lock these - * pages. So we rely upon nobody altering the ->index - * of this (pinned-by-us) page. - */ + /* We rely upon deletion not changing page->index */ index = page->index; - if (index > next) - next = index; - next++; - if (lock_failed) - continue; + if (index > end) + break; + if (!trylock_page(page)) + continue; + WARN_ON(page->index != index); ret = invalidate_inode_page(page); unlock_page(page); /* @@ -371,12 +360,11 @@ unsigned long invalidate_mapping_pages(struct address_space *mapping, if (!ret) deactivate_page(page); count += ret; - if (next > end) - break; } pagevec_release(&pvec); mem_cgroup_uncharge_end(); cond_resched(); + index++; } return count; } @@ -442,37 +430,32 @@ int invalidate_inode_pages2_range(struct address_space *mapping, pgoff_t start, pgoff_t end) { struct pagevec pvec; - pgoff_t next; + pgoff_t index; int i; int ret = 0; int ret2 = 0; int did_range_unmap = 0; - int wrapped = 0; cleancache_flush_inode(mapping); pagevec_init(&pvec, 0); - next = start; - while (next <= end && !wrapped && - pagevec_lookup(&pvec, mapping, next, - min(end - next, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) { + index = start; + while (index <= end && pagevec_lookup(&pvec, mapping, index, + min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) { mem_cgroup_uncharge_start(); for (i = 0; i < pagevec_count(&pvec); i++) { struct page *page = pvec.pages[i]; - pgoff_t page_index; + + /* We rely upon deletion not changing page->index */ + index = page->index; + if (index > end) + break; lock_page(page); + WARN_ON(page->index != index); if (page->mapping != mapping) { unlock_page(page); continue; } - page_index = page->index; - next = page_index + 1; - if (next == 0) - wrapped = 1; - if (page_index > end) { - unlock_page(page); - break; - } wait_on_page_writeback(page); if (page_mapped(page)) { if (!did_range_unmap) { @@ -480,9 +463,9 @@ int invalidate_inode_pages2_range(struct address_space *mapping, * Zap the rest of the file in one hit. */ unmap_mapping_range(mapping, - (loff_t)page_index<