On Mon, 30 May 2022, Matthew Wilcox wrote:
> On Mon, May 30, 2022 at 08:00:12AM -0400, Mikulas Patocka wrote:
> > The ntfs3 filesystem lacks the 'invalidate_folio' method and it causes
> > memory leak. If you write to the filesystem and then unmount it, the
> > cached written data are not freed and they are permanently leaked.
> >
> > Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
> > Reported-by: José Luis Lara Carrascal <manualinux@xxxxxxxx>
> > Fixes: 7ba13abbd31e ("fs: Turn block_invalidatepage into block_invalidate_folio")
>
> That commit is innocent here. Rather, this should be:
>
> Fixes: 82cae269cfa9 ("fs/ntfs3: Add initialization of super block")
82cae269cfa9 is included in the 5.15 kernel - and this bug only happens in
5.18. So, how could 82cae269cfa9 cause it?
> Yes, trees before 7ba13abbd31e will need to change the patch to add
> invalidate_page instead of invalidate_folio, but that's a normal part
> of the process.
In the kernel 5.17 and before, if the "invalidatepage" method is NULL, the
kernel will use block_invalidatepage (see do_invalidatepage). So, we don't
have to provide explicit "invalidatepage" in 5.17 and before and we don't
have to backport this bugfix there.
Note that the commit 7ba13abbd31e contains this piece of code:
-#ifdef CONFIG_BLOCK
- if (!invalidatepage)
- invalidatepage = block_invalidatepage;
-#endif
So, it explicitly breaks filesystems that have NULL invalidatepage and
NULL invalidate_folio and that relied on block_invalidatepage being called
implicitly. So, I believe this commit is the root cause of this bug.
I grepped the kernel for "dirty_folio" and it seems that ntfs3 is the only
filesystem that provides "dirty_folio" and doesn't provide
"invalidate_folio".
Mikulas
> > Cc: stable@xxxxxxxxxxxxxxx # v5.18
> >
> > ---
> > fs/ntfs3/inode.c | 1 +
> > 1 file changed, 1 insertion(+)
> >
> > Index: linux-2.6/fs/ntfs3/inode.c
> > ===================================================================
> > --- linux-2.6.orig/fs/ntfs3/inode.c 2022-05-16 16:57:24.000000000 +0200
> > +++ linux-2.6/fs/ntfs3/inode.c 2022-05-30 13:36:45.000000000 +0200
> > @@ -1951,6 +1951,7 @@ const struct address_space_operations nt
> > .direct_IO = ntfs_direct_IO,
> > .bmap = ntfs_bmap,
> > .dirty_folio = block_dirty_folio,
> > + .invalidate_folio = block_invalidate_folio,
> > };
> >
> > const struct address_space_operations ntfs_aops_cmpr = {
>
