Commit e25ff835 authored Aug 10, 2018 by Dave Jiang Committed by Darrick J. Wong Aug 12, 2018

xfs: Close race between direct IO and xfs_break_layouts()



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.

Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

parent 13942aa9

fs/xfs/xfs_file.c

+4 −5

Original line number	Diff line number	Diff line
		@@ -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);
		@@ -735,7 +733,7 @@ xfs_wait_dax_page(
		static int
		xfs_break_dax_layouts(
		struct inode *inode,
		bool *did_unlock)
		bool *retry)
		{
		struct page *page;

		@@ -745,9 +743,10 @@ 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