On Thu, Nov 19, 2015 at 04:18:13PM -0800, Dan Williams wrote:
> Neither the filemap_fault() nor the xfs dax fault path is updating time.
> This call leads to the following WARN() when the block device has been
> torn down:
I don't think that is right. In xfs_filemap_fault():
....
/* DAX can shortcut the normal fault path on write faults! */
if ((vmf->flags & FAULT_FLAG_WRITE) && IS_DAX(inode))
return xfs_filemap_page_mkwrite(vma, vmf);
....
And xfs_filemap_page_mkwrite() most definitely calls file_update_time():
....
trace_xfs_filemap_page_mkwrite(XFS_I(inode));
sb_start_pagefault(inode->i_sb);
file_update_time(vma->vm_file);
xfs_ilock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
....
And, finally, in xfs_filemap_pmd_fault():
....
if (flags & FAULT_FLAG_WRITE) {
sb_start_pagefault(inode->i_sb);
file_update_time(vma->vm_file);
}
....
So we are clearly updating timestamps in XFS on every write fault
that occurs, whether it be through ->page_mkwrite, ->fault or
->pmd_fault. Hence removing those from ext4 can't be the righ tthing
to do.
>
> WARNING: CPU: 0 PID: 2133 at fs/fs-writeback.c:2065 __mark_inode_dirty+0x261/0x350()
> bdi-block not registered
^^^^^^^^^^^^^^^^^^^^^^^^
> [..]
> Call Trace:
> [<ffffffff81459f62>] dump_stack+0x44/0x62
> [<ffffffff810a2052>] warn_slowpath_common+0x82/0xc0
> [<ffffffff810a20ec>] warn_slowpath_fmt+0x5c/0x80
> [<ffffffff812831a1>] __mark_inode_dirty+0x261/0x350
> [<ffffffff8126d109>] generic_update_time+0x79/0xd0
> [<ffffffff8126d28d>] file_update_time+0xbd/0x110
> [<ffffffff812e4bc8>] ext4_dax_fault+0x68/0x110
> [<ffffffff811f816e>] __do_fault+0x4e/0xf0
> [<ffffffff811fc2a7>] handle_mm_fault+0x5e7/0x1b50
> [<ffffffff811fbd11>] ? handle_mm_fault+0x51/0x1b50
> [<ffffffff810689c1>] __do_page_fault+0x191/0x3f0
> [<ffffffff81068cef>] trace_do_page_fault+0x4f/0x120
> [<ffffffff8106314a>] do_async_page_fault+0x1a/0xa0
> [<ffffffff81902678>] async_page_fault+0x28/0x30
Doesn't this indicate some problem at the block/bdi level?
__mark_inode_dirty() should not throw warnings like this regardless
of where it is called from...
Cheers,
Dave.
--
Dave Chinner
david@xxxxxxxxxxxxx
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