From: Theodore Ts'o Subject: [PATCH 2.6.27.y 09/11] vfs: Add no_nrwrite_index_update writeback control flag Date: Mon, 15 Mar 2010 20:26:03 -0400 Message-ID: <1268699165-17461-10-git-send-email-tytso@mit.edu> References: <1268699165-17461-1-git-send-email-tytso@mit.edu> Cc: "Jayson R. King" , Ext4 Developers List , "Aneesh Kumar K.V" , "Theodore Ts'o" , linux-fsdevel@vger.kernel.org To: stable@kernel.org Return-path: In-Reply-To: <1268699165-17461-1-git-send-email-tytso@mit.edu> Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org From: Aneesh Kumar K.V commit 17bc6c30cf6bfffd816bdc53682dd46fc34a2cf4 upstream. If no_nrwrite_index_update is set we don't update nr_to_write and address space writeback_index in write_cache_pages. This change enables a file system to skip these updates in write_cache_pages and do them in the writepages() callback. This patch will be followed by an ext4 patch that make use of these new flags. Signed-off-by: Aneesh Kumar K.V Signed-off-by: "Theodore Ts'o" CC: linux-fsdevel@vger.kernel.org [dev@jaysonking.com: Modified the patch to account for subsequent changes in mainline being cherry-picked earlier for 2.6.27.y.] Signed-off-by: Jayson R. King Signed-off-by: Theodore Ts'o --- include/linux/writeback.h | 9 +++++++++ mm/page-writeback.c | 14 +++++++++----- 2 files changed, 18 insertions(+), 5 deletions(-) diff --git a/include/linux/writeback.h b/include/linux/writeback.h index cc0e6d9..b93ab38 100644 --- a/include/linux/writeback.h +++ b/include/linux/writeback.h @@ -62,6 +62,15 @@ struct writeback_control { unsigned for_writepages:1; /* This is a writepages() call */ unsigned range_cyclic:1; /* range_start is cyclic */ unsigned more_io:1; /* more io to be dispatched */ + /* + * write_cache_pages() won't update wbc->nr_to_write and + * mapping->writeback_index if no_nrwrite_index_update + * is set. write_cache_pages() may write more than we + * requested and we want to make sure nr_to_write and + * writeback_index are updated in a consistent manner + * so we use a single control to update them + */ + unsigned no_nrwrite_index_update:1; }; /* diff --git a/mm/page-writeback.c b/mm/page-writeback.c index e5c4ca2..036dee5 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -878,6 +878,7 @@ int write_cache_pages(struct address_space *mapping, pgoff_t done_index; int cycled; int range_whole = 0; + long nr_to_write = wbc->nr_to_write; if (wbc->nonblocking && bdi_write_congested(bdi)) { wbc->encountered_congestion = 1; @@ -985,9 +986,9 @@ continue_unlock: } } - if (wbc->nr_to_write > 0) { - wbc->nr_to_write--; - if (wbc->nr_to_write == 0 && + if (nr_to_write > 0) { + nr_to_write--; + if (nr_to_write == 0 && wbc->sync_mode == WB_SYNC_NONE) { /* * We stop writing back only if we are @@ -1024,8 +1025,11 @@ continue_unlock: end = writeback_index - 1; goto retry; } - if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0)) - mapping->writeback_index = done_index; + if (!wbc->no_nrwrite_index_update) { + if (wbc->range_cyclic || (range_whole && nr_to_write > 0)) + mapping->writeback_index = done_index; + wbc->nr_to_write = nr_to_write; + } return ret; } -- 1.6.6.1.1.g974db.dirty