Messages in this thread Patch in this message | | | From | Miklos Szeredi <> | Date | Wed, 24 Nov 2021 10:23:06 +0100 | Subject | Re: [PATCH 5.15 056/917] fuse: fix page stealing |
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On Wed, Nov 24, 2021 at 1:40 AM Justin Forbes <jmforbes@linuxtx.org> wrote: > Thanks, did a scratch build for that and dropped it in the bug. Only > one user has reported back, but the report was that it did not fix the > issue. I have also gotten confirmation now that the issue is occuring > with 5.16-rc2.
Okay.
Morning light brings clarity to the mind. Here's a patch that should definitely fix this bug, as well as the very unlikely race of the page being truncated from the page cache before pipe_buf_release() is called.
Please test.
Thanks, Miklos From: Miklos Szeredi <mszeredi@redhat.com> Subject: fuse: release pipe buf after last use
Checking buf->flags should be done before the pipe_buf_release() is called on the pipe buffer, since releasing the buffer might modify the flags.
This is exactly what page_cache_pipe_buf_release() does, and which results in the same VM_BUG_ON_PAGE(PageLRU(page)) that the original patch was trying to fix.
Reported-by: Justin Forbes <jmforbes@linuxtx.org> Fixes: 712a951025c0 ("fuse: fix page stealing") Cc: <stable@vger.kernel.org> # v2.6.35 Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> --- fs/fuse/dev.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-)
--- a/fs/fuse/dev.c +++ b/fs/fuse/dev.c @@ -847,17 +847,17 @@ static int fuse_try_move_page(struct fus replace_page_cache_page(oldpage, newpage); + get_page(newpage); + + if (!(buf->flags & PIPE_BUF_FLAG_LRU)) + lru_cache_add(newpage); + /* * Release while we have extra ref on stolen page. Otherwise * anon_pipe_buf_release() might think the page can be reused. */ pipe_buf_release(cs->pipe, buf); - get_page(newpage); - - if (!(buf->flags & PIPE_BUF_FLAG_LRU)) - lru_cache_add(newpage); - err = 0; spin_lock(&cs->req->waitq.lock); if (test_bit(FR_ABORTED, &cs->req->flags)) | |