From mboxrd@z Thu Jan 1 00:00:00 1970 From: akpm@linux-foundation.org Subject: + tmpfs-convert-shmem_writepage-and-enable-swap.patch added to -mm tree Date: Fri, 17 Jun 2011 16:40:05 -0700 Message-ID: <201106172340.p5HNe5Te008323@imap1.linux-foundation.org> Reply-To: linux-kernel@vger.kernel.org Return-path: Received: from smtp1.linux-foundation.org ([140.211.169.13]:39595 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759588Ab1FQXkK (ORCPT ); Fri, 17 Jun 2011 19:40:10 -0400 Sender: mm-commits-owner@vger.kernel.org List-Id: mm-commits@vger.kernel.org To: mm-commits@vger.kernel.org Cc: hughd@google.com, riel@redhat.com The patch titled tmpfs: convert shmem_writepage and enable swap has been added to the -mm tree. Its filename is tmpfs-convert-shmem_writepage-and-enable-swap.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** See http://userweb.kernel.org/~akpm/stuff/added-to-mm.txt to find out what to do about this The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ ------------------------------------------------------ Subject: tmpfs: convert shmem_writepage and enable swap From: Hugh Dickins Convert shmem_writepage() to use shmem_delete_from_page_cache() to use shmem_radix_tree_replace() to substitute swap entry for page pointer atomically in the radix tree. As with shmem_add_to_page_cache(), it's not entirely satisfactory to be copying such code from delete_from_swap_cache, but again judged easier to sell than making its other callers go through the extras. Remove the toy implementation's shmem_put_swap() and shmem_get_swap(), now unreferenced, and the hack to disable swap: it's now good to go. The way things have worked out, info->lock no longer helps to guard the shmem_swaplist: we increment swapped under shmem_swaplist_mutex only. That global mutex exclusion between shmem_writepage() and shmem_unuse() is not pretty, and we ought to find another way; but it's been forced on us by recent race discoveries, not a consequence of this patchset. And what has become of the WARN_ON_ONCE(1) free_swap_and_cache() if a swap entry was found already present? That's no longer possible, the (unknown) one inserting this page into filecache would hit the swap entry occupying that slot. Signed-off-by: Hugh Dickins Acked-by: Rik van Riel Signed-off-by: Andrew Morton --- mm/shmem.c | 88 +++++++++++++++++++++------------------------------ 1 file changed, 37 insertions(+), 51 deletions(-) diff -puN mm/shmem.c~tmpfs-convert-shmem_writepage-and-enable-swap mm/shmem.c --- a/mm/shmem.c~tmpfs-convert-shmem_writepage-and-enable-swap +++ a/mm/shmem.c @@ -6,7 +6,8 @@ * 2000-2001 Christoph Rohland * 2000-2001 SAP AG * 2002 Red Hat Inc. - * Copyright (C) 2002-2005 Hugh Dickins. + * Copyright (C) 2002-2011 Hugh Dickins. + * Copyright (C) 2011 Google Inc. * Copyright (C) 2002-2005 VERITAS Software Corporation. * Copyright (C) 2004 Andi Kleen, SuSE Labs * @@ -219,19 +220,6 @@ static void shmem_recalc_inode(struct in } } -static void shmem_put_swap(struct shmem_inode_info *info, pgoff_t index, - swp_entry_t swap) -{ - if (index < SHMEM_NR_DIRECT) - info->i_direct[index] = swap; -} - -static swp_entry_t shmem_get_swap(struct shmem_inode_info *info, pgoff_t index) -{ - return (index < SHMEM_NR_DIRECT) ? - info->i_direct[index] : (swp_entry_t){0}; -} - /* * Replace item expected in radix tree by a new item, while holding tree lock. */ @@ -300,6 +288,25 @@ static int shmem_add_to_page_cache(struc } /* + * Like delete_from_page_cache, but substitutes swap for page. + */ +static void shmem_delete_from_page_cache(struct page *page, void *radswap) +{ + struct address_space *mapping = page->mapping; + int error; + + spin_lock_irq(&mapping->tree_lock); + error = shmem_radix_tree_replace(mapping, page->index, page, radswap); + page->mapping = NULL; + mapping->nrpages--; + __dec_zone_page_state(page, NR_FILE_PAGES); + __dec_zone_page_state(page, NR_SHMEM); + spin_unlock_irq(&mapping->tree_lock); + page_cache_release(page); + BUG_ON(error); +} + +/* * Like find_get_pages, but collecting swap entries as well as pages. */ static unsigned shmem_find_get_pages_and_swap(struct address_space *mapping, @@ -664,14 +671,10 @@ int shmem_unuse(swp_entry_t swap, struct mutex_lock(&shmem_swaplist_mutex); list_for_each_safe(this, next, &shmem_swaplist) { info = list_entry(this, struct shmem_inode_info, swaplist); - if (!info->swapped) { - spin_lock(&info->lock); - if (!info->swapped) - list_del_init(&info->swaplist); - spin_unlock(&info->lock); - } if (info->swapped) found = shmem_unuse_inode(info, swap, page); + else + list_del_init(&info->swaplist); cond_resched(); if (found) break; @@ -694,10 +697,10 @@ out: static int shmem_writepage(struct page *page, struct writeback_control *wbc) { struct shmem_inode_info *info; - swp_entry_t swap, oswap; struct address_space *mapping; - pgoff_t index; struct inode *inode; + swp_entry_t swap; + pgoff_t index; BUG_ON(!PageLocked(page)); mapping = page->mapping; @@ -720,55 +723,38 @@ static int shmem_writepage(struct page * WARN_ON_ONCE(1); /* Still happens? Tell us about it! */ goto redirty; } - - /* - * Disable even the toy swapping implementation, while we convert - * functions one by one to having swap entries in the radix tree. - */ - if (index < ULONG_MAX) - goto redirty; - swap = get_swap_page(); if (!swap.val) goto redirty; /* * Add inode to shmem_unuse()'s list of swapped-out inodes, - * if it's not already there. Do it now because we cannot take - * mutex while holding spinlock, and must do so before the page - * is moved to swap cache, when its pagelock no longer protects + * if it's not already there. Do it now before the page is + * moved to swap cache, when its pagelock no longer protects * the inode from eviction. But don't unlock the mutex until - * we've taken the spinlock, because shmem_unuse_inode() will - * prune a !swapped inode from the swaplist under both locks. + * we've incremented swapped, because shmem_unuse_inode() will + * prune a !swapped inode from the swaplist under this mutex. */ mutex_lock(&shmem_swaplist_mutex); if (list_empty(&info->swaplist)) list_add_tail(&info->swaplist, &shmem_swaplist); - spin_lock(&info->lock); - mutex_unlock(&shmem_swaplist_mutex); - - oswap = shmem_get_swap(info, index); - if (oswap.val) { - WARN_ON_ONCE(1); /* Still happens? Tell us about it! */ - free_swap_and_cache(oswap); - shmem_put_swap(info, index, (swp_entry_t){0}); - info->swapped--; - } - shmem_recalc_inode(inode); - if (add_to_swap_cache(page, swap, GFP_ATOMIC) == 0) { - delete_from_page_cache(page); - shmem_put_swap(info, index, swap); - info->swapped++; swap_shmem_alloc(swap); + shmem_delete_from_page_cache(page, swp_to_radix_entry(swap)); + + spin_lock(&info->lock); + info->swapped++; + shmem_recalc_inode(inode); spin_unlock(&info->lock); + + mutex_unlock(&shmem_swaplist_mutex); BUG_ON(page_mapped(page)); swap_writepage(page, wbc); return 0; } - spin_unlock(&info->lock); + mutex_unlock(&shmem_swaplist_mutex); swapcache_free(swap, NULL); redirty: set_page_dirty(page); _ Patches currently in -mm which might be from hughd@google.com are origin.patch mm-move-vmtruncate_range-to-truncatec.patch mm-move-shmem-prototypes-to-shmem_fsh.patch tmpfs-take-control-of-its-truncate_range.patch tmpfs-add-shmem_read_mapping_page_gfp.patch drm-ttm-use-shmem_read_mapping_page.patch drm-i915-use-shmem_read_mapping_page.patch drm-i915-use-shmem_truncate_range.patch drm-i915-more-struct_mutex-locking.patch drm-i915-more-struct_mutex-locking-fix.patch mm-cleanup-descriptions-of-filler-arg.patch mm-truncate-functions-are-in-truncatec.patch mm-tidy-vmtruncate_range-and-related-functions.patch mm-consistent-truncate-and-invalidate-loops.patch mm-pincer-in-truncate_inode_pages_range.patch tmpfs-no-need-to-use-i_lock.patch linux-next.patch tmpfs-clone-shmem_file_splice_read.patch tmpfs-refine-shmem_file_splice_read.patch tmpfs-pass-gfp-to-shmem_getpage_gfp.patch tmpfs-remove_shmem_readpage.patch tmpfs-simplify-prealloc_page.patch tmpfs-simplify-filepage-swappage.patch tmpfs-simplify-unuse-and-writepage.patch radix_tree-exceptional-entries-and-indices.patch mm-let-swap-use-exceptional-entries.patch tmpfs-demolish-old-swap-vector-support.patch tmpfs-miscellaneous-trivial-cleanups.patch tmpfs-copy-truncate_inode_pages_range.patch tmpfs-convert-shmem_truncate_range-to-radix-swap.patch tmpfs-convert-shmem_unuse_inode-to-radix-swap.patch tmpfs-convert-shmem_getpage_gfp-to-radix-swap.patch tmpfs-convert-mem_cgroup-shmem-to-radix-swap.patch tmpfs-convert-shmem_writepage-and-enable-swap.patch tmpfs-use-kmemdup-for-short-symlinks.patch mm-a-few-small-updates-for-radix-swap.patch prio_tree-debugging-patch.patch