ext4: fix data integrity sync in ordered mode

When we perform a data integrity sync we tag all the dirty pages with
PAGECACHE_TAG_TOWRITE at start of ext4_da_writepages.  Later we check
for this tag in write_cache_pages_da and creates a struct
mpage_da_data containing contiguously indexed pages tagged with this
tag and sync these pages with a call to mpage_da_map_and_submit.  This
process is done in while loop until all the PAGECACHE_TAG_TOWRITE
pages are synced. We also do journal start and stop in each iteration.
journal_stop could initiate journal commit which would call
ext4_writepage which in turn will call ext4_bio_write_page even for
delayed OR unwritten buffers. When ext4_bio_write_page is called for
such buffers, even though it does not sync them but it clears the
PAGECACHE_TAG_TOWRITE of the corresponding page and hence these pages
are also not synced by the currently running data integrity sync. We
will end up with dirty pages although sync is completed.

This could cause a potential data loss when the sync call is followed
by a truncate_pagecache call, which is exactly the case in
collapse_range.  (It will cause generic/127 failure in xfstests)

To avoid this issue, we can use set_page_writeback_keepwrite instead of
set_page_writeback, which doesn't clear TOWRITE tag.

Cc: stable@vger.kernel.org
Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>
Signed-off-by: Ashish Sangwan <a.sangwan@samsung.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Reviewed-by: Jan Kara <jack@suse.cz>

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 1d08a1b51bdd806127b6582b6a8b622cee0765f6..aeda5061a59a51bc44634d0f0722781f236e2500 100644 (file)
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -2772,7 +2772,8 @@ extern void ext4_io_submit(struct ext4_io_submit *io);
 extern int ext4_bio_write_page(struct ext4_io_submit *io,
                               struct page *page,
                               int len,
-                              struct writeback_control *wbc);
+                              struct writeback_control *wbc,
+                              bool keep_towrite);
 
 /* mmp.c */
 extern int ext4_multi_mount_protect(struct super_block *, ext4_fsblk_t);

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 9b3c52fbe86de0b487694b1fccccfa28631ce410..04dd2de10796c9759f224f1a10e6af5e2138a59d 100644 (file)
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1846,6 +1846,7 @@ static int ext4_writepage(struct page *page,
        struct buffer_head *page_bufs = NULL;
        struct inode *inode = page->mapping->host;
        struct ext4_io_submit io_submit;
+       bool keep_towrite = false;
 
        trace_ext4_writepage(page);
        size = i_size_read(inode);
@@ -1876,6 +1877,7 @@ static int ext4_writepage(struct page *page,
                        unlock_page(page);
                        return 0;
                }
+               keep_towrite = true;
        }
 
        if (PageChecked(page) && ext4_should_journal_data(inode))
@@ -1892,7 +1894,7 @@ static int ext4_writepage(struct page *page,
                unlock_page(page);
                return -ENOMEM;
        }
-       ret = ext4_bio_write_page(&io_submit, page, len, wbc);
+       ret = ext4_bio_write_page(&io_submit, page, len, wbc, keep_towrite);
        ext4_io_submit(&io_submit);
        /* Drop io_end reference we got from init */
        ext4_put_io_end_defer(io_submit.io_end);
@@ -1911,7 +1913,7 @@ static int mpage_submit_page(struct mpage_da_data *mpd, struct page *page)
        else
                len = PAGE_CACHE_SIZE;
        clear_page_dirty_for_io(page);
-       err = ext4_bio_write_page(&mpd->io_submit, page, len, mpd->wbc);
+       err = ext4_bio_write_page(&mpd->io_submit, page, len, mpd->wbc, false);
        if (!err)
                mpd->wbc->nr_to_write--;
        mpd->first_page++;

diff --git a/fs/ext4/page-io.c b/fs/ext4/page-io.c
index c18d95b5054081c75e0c7a2fab975976838f9b02..4cb2743cb2e3a47c28696f68002614dbbc0aceef 100644 (file)
--- a/fs/ext4/page-io.c
+++ b/fs/ext4/page-io.c
@@ -401,7 +401,8 @@ submit_and_retry:
 int ext4_bio_write_page(struct ext4_io_submit *io,
                        struct page *page,
                        int len,
-                       struct writeback_control *wbc)
+                       struct writeback_control *wbc,
+                       bool keep_towrite)
 {
        struct inode *inode = page->mapping->host;
        unsigned block_start, blocksize;
@@ -414,7 +415,10 @@ int ext4_bio_write_page(struct ext4_io_submit *io,
        BUG_ON(!PageLocked(page));
        BUG_ON(PageWriteback(page));
 
-       set_page_writeback(page);
+       if (keep_towrite)
+               set_page_writeback_keepwrite(page);
+       else
+               set_page_writeback(page);
        ClearPageError(page);
 
        /*

diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index d1fe1a761047683e555a9544dd5c668d5ae6752b..ca71a1d347a0870666faad2f76cbf55230bbe2e4 100644 (file)
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -317,13 +317,23 @@ CLEARPAGEFLAG(Uptodate, uptodate)
 extern void cancel_dirty_page(struct page *page, unsigned int account_size);
 
 int test_clear_page_writeback(struct page *page);
-int test_set_page_writeback(struct page *page);
+int __test_set_page_writeback(struct page *page, bool keep_write);
+
+#define test_set_page_writeback(page)                  \
+       __test_set_page_writeback(page, false)
+#define test_set_page_writeback_keepwrite(page)        \
+       __test_set_page_writeback(page, true)
 
 static inline void set_page_writeback(struct page *page)
 {
        test_set_page_writeback(page);
 }
 
+static inline void set_page_writeback_keepwrite(struct page *page)
+{
+       test_set_page_writeback_keepwrite(page);
+}
+
 #ifdef CONFIG_PAGEFLAGS_EXTENDED
 /*
  * System with lots of page flags available. This allows separate

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index ef413492a14945c5e7ab0f5a8d33bd66eaf34873..d8691d9de3c427b6347f92115726eda825ffa01b 100644 (file)
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -2398,7 +2398,7 @@ int test_clear_page_writeback(struct page *page)
        return ret;
 }
 
-int test_set_page_writeback(struct page *page)
+int __test_set_page_writeback(struct page *page, bool keep_write)
 {
        struct address_space *mapping = page_mapping(page);
        int ret;
@@ -2423,9 +2423,10 @@ int test_set_page_writeback(struct page *page)
                        radix_tree_tag_clear(&mapping->page_tree,
                                                page_index(page),
                                                PAGECACHE_TAG_DIRTY);
-               radix_tree_tag_clear(&mapping->page_tree,
-                                    page_index(page),
-                                    PAGECACHE_TAG_TOWRITE);
+               if (!keep_write)
+                       radix_tree_tag_clear(&mapping->page_tree,
+                                               page_index(page),
+                                               PAGECACHE_TAG_TOWRITE);
                spin_unlock_irqrestore(&mapping->tree_lock, flags);
        } else {
                ret = TestSetPageWriteback(page);
@@ -2436,7 +2437,7 @@ int test_set_page_writeback(struct page *page)
        return ret;
 
 }
-EXPORT_SYMBOL(test_set_page_writeback);
+EXPORT_SYMBOL(__test_set_page_writeback);
 
 /*
  * Return true if any of the pages in the mapping are marked with the