jffs2: Hook up splice_write callback

Message ID 20210330134537.423447-1-joel@jms.id.au
State New
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Series
  • jffs2: Hook up splice_write callback
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Commit Message

Joel Stanley March 30, 2021, 1:45 p.m.
overlayfs using jffs2 as the upper filesystem would fail in some cases
since moving to v5.10. The test case used was to run 'touch' on a file
that exists in the lower fs, causing the modification time to be
updated. It returns EINVAL when the bug is triggered.

A bisection showed this was introduced in v5.9-rc1, with commit
36e2c7421f02 ("fs: don't allow splice read/write without explicit ops").
Reverting that commit restores the expected behaviour.

Some digging showed that this was due to jffs2 lacking an implementation
of splice_write. (For unknown reasons the warn_unsupported that should
trigger was not displaying any output).

Adding this patch resolved the issue and the test now passes.

Fixes: 36e2c7421f02 ("fs: don't allow splice read/write without explicit ops")
Signed-off-by: Joel Stanley <joel@jms.id.au>

---
 fs/jffs2/file.c | 1 +
 1 file changed, 1 insertion(+)

-- 
2.30.2


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Comments

Christoph Hellwig March 30, 2021, 4:17 p.m. | #1
On Wed, Mar 31, 2021 at 12:15:37AM +1030, Joel Stanley wrote:
> overlayfs using jffs2 as the upper filesystem would fail in some cases

> since moving to v5.10. The test case used was to run 'touch' on a file

> that exists in the lower fs, causing the modification time to be

> updated. It returns EINVAL when the bug is triggered.

> 

> A bisection showed this was introduced in v5.9-rc1, with commit

> 36e2c7421f02 ("fs: don't allow splice read/write without explicit ops").

> Reverting that commit restores the expected behaviour.

> 

> Some digging showed that this was due to jffs2 lacking an implementation

> of splice_write. (For unknown reasons the warn_unsupported that should

> trigger was not displaying any output).

> 

> Adding this patch resolved the issue and the test now passes.


Looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>


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Al Viro March 30, 2021, 6:31 p.m. | #2
On Tue, Mar 30, 2021 at 06:17:15PM +0200, Christoph Hellwig wrote:
> On Wed, Mar 31, 2021 at 12:15:37AM +1030, Joel Stanley wrote:

> > overlayfs using jffs2 as the upper filesystem would fail in some cases

> > since moving to v5.10. The test case used was to run 'touch' on a file

> > that exists in the lower fs, causing the modification time to be

> > updated. It returns EINVAL when the bug is triggered.

> > 

> > A bisection showed this was introduced in v5.9-rc1, with commit

> > 36e2c7421f02 ("fs: don't allow splice read/write without explicit ops").

> > Reverting that commit restores the expected behaviour.

> > 

> > Some digging showed that this was due to jffs2 lacking an implementation

> > of splice_write. (For unknown reasons the warn_unsupported that should

> > trigger was not displaying any output).

> > 

> > Adding this patch resolved the issue and the test now passes.

> 

> Looks good:

> 

> Reviewed-by: Christoph Hellwig <hch@lst.de>


The same goes for quite a few other filesystems, actually - at least
adfs, affs, bfs, hfs, hfsplus, hostfs, hpfs, minix, omfs, sysv, ufs 
and vboxsf are in the same boat, and I suspect that ecryptfs and ntfs
might be too.

Christoph, do you see any problems with doing the same thing for that
bunch as well?

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Al Viro March 30, 2021, 6:38 p.m. | #3
On Tue, Mar 30, 2021 at 06:31:00PM +0000, Al Viro wrote:
> On Tue, Mar 30, 2021 at 06:17:15PM +0200, Christoph Hellwig wrote:

> > On Wed, Mar 31, 2021 at 12:15:37AM +1030, Joel Stanley wrote:

> > > overlayfs using jffs2 as the upper filesystem would fail in some cases

> > > since moving to v5.10. The test case used was to run 'touch' on a file

> > > that exists in the lower fs, causing the modification time to be

> > > updated. It returns EINVAL when the bug is triggered.

> > > 

> > > A bisection showed this was introduced in v5.9-rc1, with commit

> > > 36e2c7421f02 ("fs: don't allow splice read/write without explicit ops").

> > > Reverting that commit restores the expected behaviour.

> > > 

> > > Some digging showed that this was due to jffs2 lacking an implementation

> > > of splice_write. (For unknown reasons the warn_unsupported that should

> > > trigger was not displaying any output).

> > > 

> > > Adding this patch resolved the issue and the test now passes.

> > 

> > Looks good:

> > 

> > Reviewed-by: Christoph Hellwig <hch@lst.de>

> 

> The same goes for quite a few other filesystems, actually - at least

> adfs, affs, bfs, hfs, hfsplus, hostfs, hpfs, minix, omfs, sysv, ufs 

> and vboxsf are in the same boat, and I suspect that ecryptfs and ntfs

> might be too.

> 

> Christoph, do you see any problems with doing the same thing for that

> bunch as well?


coda and udf as well, by the look of it...

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Lei YU March 31, 2021, 4:55 a.m. | #4
On Tue, Mar 30, 2021 at 9:45 PM Joel Stanley <joel@jms.id.au> wrote:
>

> overlayfs using jffs2 as the upper filesystem would fail in some cases

> since moving to v5.10. The test case used was to run 'touch' on a file

> that exists in the lower fs, causing the modification time to be

> updated. It returns EINVAL when the bug is triggered.

>

> A bisection showed this was introduced in v5.9-rc1, with commit

> 36e2c7421f02 ("fs: don't allow splice read/write without explicit ops").

> Reverting that commit restores the expected behaviour.

>

> Some digging showed that this was due to jffs2 lacking an implementation

> of splice_write. (For unknown reasons the warn_unsupported that should

> trigger was not displaying any output).

>

> Adding this patch resolved the issue and the test now passes.

>

> Fixes: 36e2c7421f02 ("fs: don't allow splice read/write without explicit ops")

> Signed-off-by: Joel Stanley <joel@jms.id.au>

> ---

>  fs/jffs2/file.c | 1 +

>  1 file changed, 1 insertion(+)

>

> diff --git a/fs/jffs2/file.c b/fs/jffs2/file.c

> index f8fb89b10227..4fc8cd698d1a 100644

> --- a/fs/jffs2/file.c

> +++ b/fs/jffs2/file.c

> @@ -57,6 +57,7 @@ const struct file_operations jffs2_file_operations =

>         .mmap =         generic_file_readonly_mmap,

>         .fsync =        jffs2_fsync,

>         .splice_read =  generic_file_splice_read,

> +       .splice_write = iter_file_splice_write,

>  };

>

>  /* jffs2_file_inode_operations */

> --

> 2.30.2

>


Verified on g220a openbmc system that the patch fixes the issue.

Tested-by: Lei YU <yulei.sh@bytedance.com>


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Christoph Hellwig March 31, 2021, 2:44 p.m. | #5
On Tue, Mar 30, 2021 at 06:31:00PM +0000, Al Viro wrote:
> The same goes for quite a few other filesystems, actually - at least

> adfs, affs, bfs, hfs, hfsplus, hostfs, hpfs, minix, omfs, sysv, ufs 

> and vboxsf are in the same boat, and I suspect that ecryptfs and ntfs

> might be too.

> 

> Christoph, do you see any problems with doing the same thing for that

> bunch as well?


Linus asked to only fix things up where we get reports, but I think his
intent there was more random procfs and debugfs files rather than file
systems.  So just doing the sweep should be fine.

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Patch

diff --git a/fs/jffs2/file.c b/fs/jffs2/file.c
index f8fb89b10227..4fc8cd698d1a 100644
--- a/fs/jffs2/file.c
+++ b/fs/jffs2/file.c
@@ -57,6 +57,7 @@  const struct file_operations jffs2_file_operations =
 	.mmap =		generic_file_readonly_mmap,
 	.fsync =	jffs2_fsync,
 	.splice_read =	generic_file_splice_read,
+	.splice_write = iter_file_splice_write,
 };
 
 /* jffs2_file_inode_operations */