| Message ID | 1379705714-16260-1-git-send-email-luis.henriques@canonical.com |
|---|---|
| State | New |
| Headers | show |
diff --git a/fs/fuse/file.c b/fs/fuse/file.c index 514f12a..e7785e4 100644 --- a/fs/fuse/file.c +++ b/fs/fuse/file.c @@ -1296,7 +1296,6 @@ static int fuse_writepage_locked(struct page *page) inc_bdi_stat(mapping->backing_dev_info, BDI_WRITEBACK); inc_zone_page_state(tmp_page, NR_WRITEBACK_TEMP); - end_page_writeback(page); spin_lock(&fc->lock); list_add(&req->writepages_entry, &fi->writepages); @@ -1304,6 +1303,8 @@ static int fuse_writepage_locked(struct page *page) fuse_flush_writepages(inode); spin_unlock(&fc->lock); + end_page_writeback(page); + return 0; err_free:
This is a note to let you know that I have just added a patch titled fuse: postpone end_page_writeback() in to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree which can be found at: http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 3.5.y.z tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Luis ------ From f234ac58828c76331aa12c43ff2c4e2f77cc7844 Mon Sep 17 00:00:00 2001 From: Maxim Patlasov <MPatlasov@parallels.com> Date: Mon, 12 Aug 2013 20:39:30 +0400 Subject: [PATCH] fuse: postpone end_page_writeback() in fuse_writepage_locked() commit 4a4ac4eba1010ef9a804569058ab29e3450c0315 upstream. The patch fixes a race between ftruncate(2), mmap-ed write and write(2): 1) An user makes a page dirty via mmap-ed write. 2) The user performs shrinking truncate(2) intended to purge the page. 3) Before fuse_do_setattr calls truncate_pagecache, the page goes to writeback. fuse_writepage_locked fills FUSE_WRITE request and releases the original page by end_page_writeback. 4) fuse_do_setattr() completes and successfully returns. Since now, i_mutex is free. 5) Ordinary write(2) extends i_size back to cover the page. Note that fuse_send_write_pages do wait for fuse writeback, but for another page->index. 6) fuse_writepage_locked proceeds by queueing FUSE_WRITE request. fuse_send_writepage is supposed to crop inarg->size of the request, but it doesn't because i_size has already been extended back. Moving end_page_writeback to the end of fuse_writepage_locked fixes the race because now the fact that truncate_pagecache is successfully returned infers that fuse_writepage_locked has already called end_page_writeback. And this, in turn, infers that fuse_flush_writepages has already called fuse_send_writepage, and the latter used valid (shrunk) i_size. write(2) could not extend it because of i_mutex held by ftruncate(2). Signed-off-by: Maxim Patlasov <mpatlasov@parallels.com> Signed-off-by: Miklos Szeredi <mszeredi@suse.cz> Signed-off-by: Luis Henriques <luis.henriques@canonical.com> --- fs/fuse/file.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) -- 1.8.3.2