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author | Xie Xiaobo <xiaobo.xie@nxp.com> | 2017-12-12 08:12:33 (GMT) |
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committer | Xie Xiaobo <xiaobo.xie@nxp.com> | 2017-12-12 08:12:33 (GMT) |
commit | c0246a9ec4d461ef4dd7647f94005380bb9e7f0b (patch) | |
tree | 7588601aa6ce98f5e9fd083a1b351d9023c0b295 /fs/ext4/inode.c | |
parent | 50fd1a6d79d48a7c35890aecce5a5d6b872a461d (diff) | |
parent | 56f4a560c6d6318b5a8e18a1b3e44909a5158d1e (diff) | |
download | linux-c0246a9ec4d461ef4dd7647f94005380bb9e7f0b.tar.xz |
Merge Linaro linux 4.9.62 into linux-4.9
Signed-off-by: Xiaobo Xie <xiaobo.xie@nxp.com>
Diffstat (limited to 'fs/ext4/inode.c')
-rw-r--r-- | fs/ext4/inode.c | 18 |
1 files changed, 16 insertions, 2 deletions
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 1b29efc..ec28e8e 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -2107,15 +2107,29 @@ static int ext4_writepage(struct page *page, static int mpage_submit_page(struct mpage_da_data *mpd, struct page *page) { int len; - loff_t size = i_size_read(mpd->inode); + loff_t size; int err; BUG_ON(page->index != mpd->first_page); + clear_page_dirty_for_io(page); + /* + * We have to be very careful here! Nothing protects writeback path + * against i_size changes and the page can be writeably mapped into + * page tables. So an application can be growing i_size and writing + * data through mmap while writeback runs. clear_page_dirty_for_io() + * write-protects our page in page tables and the page cannot get + * written to again until we release page lock. So only after + * clear_page_dirty_for_io() we are safe to sample i_size for + * ext4_bio_write_page() to zero-out tail of the written page. We rely + * on the barrier provided by TestClearPageDirty in + * clear_page_dirty_for_io() to make sure i_size is really sampled only + * after page tables are updated. + */ + size = i_size_read(mpd->inode); if (page->index == size >> PAGE_SHIFT) len = size & ~PAGE_MASK; else len = PAGE_SIZE; - clear_page_dirty_for_io(page); err = ext4_bio_write_page(&mpd->io_submit, page, len, mpd->wbc, false); if (!err) mpd->wbc->nr_to_write--; |