On 8/8/18 12:31 PM, Dave Jiang wrote:
> This patch is the duplicate of ross's fix for ext4 for xfs.
>
> If the refcount of a page is lowered between the time that it is returned
> by dax_busy_page() and when the refcount is again checked in
> xfs_break_layouts() => ___wait_var_event(), the waiting function
> xfs_wait_dax_page() will never be called. This means that
> xfs_break_layouts() will still have 'retry' set to false, so we'll stop
> looping and never check the refcount of other pages in this inode.
>
> Instead, always continue looping as long as dax_layout_busy_page() gives us
> a page which it found with an elevated refcount.
Hi Dave, does this have a testcase? Have you seen the issue using Ross's
xfstest generic/503 or is there some other test? Apologies if I missed
prior discussion on a testcase or race frequency...
Thanks,
-Eric
> Signed-off-by: Dave Jiang <dave.jiang@xxxxxxxxx>
> Reviewed-by: Jan Kara <jack@xxxxxxx>
> ---
>
> Sorry resend, forgot to add Jan's reviewed-by.
>
> v2:
> - Rename parameter from did_unlock to retry (Jan)
>
> fs/xfs/xfs_file.c | 9 ++++-----
> 1 file changed, 4 insertions(+), 5 deletions(-)
>
> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> index a3e7767a5715..cd6f0d8c4922 100644
> --- a/fs/xfs/xfs_file.c
> +++ b/fs/xfs/xfs_file.c
> @@ -721,12 +721,10 @@ xfs_file_write_iter(
>
> static void
> xfs_wait_dax_page(
> - struct inode *inode,
> - bool *did_unlock)
> + struct inode *inode)
> {
> struct xfs_inode *ip = XFS_I(inode);
>
> - *did_unlock = true;
> xfs_iunlock(ip, XFS_MMAPLOCK_EXCL);
> schedule();
> xfs_ilock(ip, XFS_MMAPLOCK_EXCL);
> @@ -736,7 +734,7 @@ static int
> xfs_break_dax_layouts(
> struct inode *inode,
> uint iolock,
> - bool *did_unlock)
> + bool *retry)
> {
> struct page *page;
>
> @@ -746,9 +744,10 @@ xfs_break_dax_layouts(
> if (!page)
> return 0;
>
> + *retry = true;
> return ___wait_var_event(&page->_refcount,
> atomic_read(&page->_refcount) == 1, TASK_INTERRUPTIBLE,
> - 0, 0, xfs_wait_dax_page(inode, did_unlock));
> + 0, 0, xfs_wait_dax_page(inode));
> }
>
> int
>
