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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>
This commit is contained in:
Dave Jiang 2018-08-10 08:48:18 -07:00 committed by Darrick J. Wong
parent 13942aa94a
commit e25ff835af
1 changed files with 4 additions and 5 deletions
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9
fs/xfs/xfs_file.c
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@ -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