From: Peter Zijlstra Subject: [PATCH 26/31] nfs: disable data cache revalidation for swapfiles Patch-mainline: Not yet Do as Trond suggested: http://lkml.org/lkml/2006/8/25/348 Disable NFS data cache revalidation on swap files since it doesn't really make sense to have other clients change the file while you are using it. Thereby we can stop setting PG_private on swap pages, since there ought to be no further races with invalidate_inode_pages2() to deal with. And since we cannot set PG_private we cannot use page->private (which is already used by PG_swapcache pages anyway) to store the nfs_page. Thus augment the new nfs_page_find_request logic. Signed-off-by: Peter Zijlstra Signed-off-by: Suresh Jayaraman --- fs/nfs/inode.c | 6 ++++ fs/nfs/write.c | 71 +++++++++++++++++++++++++++++++++++++++++++++++---------- 2 files changed, 65 insertions(+), 12 deletions(-) --- a/fs/nfs/inode.c +++ b/fs/nfs/inode.c @@ -780,6 +780,12 @@ int nfs_revalidate_mapping(struct inode struct nfs_inode *nfsi = NFS_I(inode); int ret = 0; + /* + * swapfiles are not supposed to be shared. + */ + if (IS_SWAPFILE(inode)) + goto out; + if ((nfsi->cache_validity & NFS_INO_REVAL_PAGECACHE) || nfs_attribute_timeout(inode) || NFS_STALE(inode)) { ret = __nfs_revalidate_inode(NFS_SERVER(inode), inode); --- a/fs/nfs/write.c +++ b/fs/nfs/write.c @@ -109,25 +109,64 @@ static void nfs_context_set_write_error( set_bit(NFS_CONTEXT_ERROR_WRITE, &ctx->flags); } -static struct nfs_page *nfs_page_find_request_locked(struct page *page) +static struct nfs_page * +__nfs_page_find_request_locked(struct nfs_inode *nfsi, struct page *page, + int get) { struct nfs_page *req = NULL; - if (PagePrivate(page)) { + if (PagePrivate(page)) req = (struct nfs_page *)page_private(page); - if (req != NULL) - kref_get(&req->wb_kref); - } + else if (unlikely(PageSwapCache(page))) + req = radix_tree_lookup(&nfsi->nfs_page_tree, + page_file_index(page)); + + if (get && req) + kref_get(&req->wb_kref); + return req; } +static inline struct nfs_page * +nfs_page_find_request_locked(struct nfs_inode *nfsi, struct page *page) +{ + return __nfs_page_find_request_locked(nfsi, page, 1); +} + +static int __nfs_page_has_request(struct page *page) +{ + struct inode *inode = page_file_mapping(page)->host; + struct nfs_page *req = NULL; + + spin_lock(&inode->i_lock); + req = __nfs_page_find_request_locked(NFS_I(inode), page, 0); + spin_unlock(&inode->i_lock); + + /* + * hole here plugged by the caller holding onto PG_locked + */ + + return req != NULL; +} + +static inline int nfs_page_has_request(struct page *page) +{ + if (PagePrivate(page)) + return 1; + + if (unlikely(PageSwapCache(page))) + return __nfs_page_has_request(page); + + return 0; +} + static struct nfs_page *nfs_page_find_request(struct page *page) { struct inode *inode = page_file_mapping(page)->host; struct nfs_page *req = NULL; spin_lock(&inode->i_lock); - req = nfs_page_find_request_locked(page); + req = nfs_page_find_request_locked(NFS_I(inode), page); spin_unlock(&inode->i_lock); return req; } @@ -228,7 +267,7 @@ static struct nfs_page *nfs_find_and_loc spin_lock(&inode->i_lock); for (;;) { - req = nfs_page_find_request_locked(page); + req = nfs_page_find_request_locked(NFS_I(inode), page); if (req == NULL) break; if (nfs_set_page_tag_locked(req)) @@ -382,8 +421,14 @@ static int nfs_inode_add_request(struct if (nfs_have_delegation(inode, FMODE_WRITE)) nfsi->change_attr++; } - SetPagePrivate(req->wb_page); - set_page_private(req->wb_page, (unsigned long)req); + /* + * Swap-space should not get truncated. Hence no need to plug the race + * with invalidate/truncate. + */ + if (likely(!PageSwapCache(req->wb_page))) { + SetPagePrivate(req->wb_page); + set_page_private(req->wb_page, (unsigned long)req); + } nfsi->npages++; kref_get(&req->wb_kref); radix_tree_tag_set(&nfsi->nfs_page_tree, req->wb_index, @@ -405,8 +450,10 @@ static void nfs_inode_remove_request(str BUG_ON (!NFS_WBACK_BUSY(req)); spin_lock(&inode->i_lock); - set_page_private(req->wb_page, 0); - ClearPagePrivate(req->wb_page); + if (likely(!PageSwapCache(req->wb_page))) { + set_page_private(req->wb_page, 0); + ClearPagePrivate(req->wb_page); + } radix_tree_delete(&nfsi->nfs_page_tree, req->wb_index); nfsi->npages--; if (!nfsi->npages) { @@ -574,7 +621,7 @@ static struct nfs_page *nfs_try_to_updat spin_lock(&inode->i_lock); for (;;) { - req = nfs_page_find_request_locked(page); + req = nfs_page_find_request_locked(NFS_I(inode), page); if (req == NULL) goto out_unlock;