[PATCH 1/5] fs: ext4: initialize fsdata in pagecache_write()

[PATCH 1/5] fs: ext4: initialize fsdata in pagecache_write()

[Alexander Potapenko]

When aops->write_begin() does not initialize fsdata, KMSAN reports
an error passing the latter to aops->write_end().

Fix this by unconditionally initializing fsdata.

Cc: Eric Biggers <ebiggers@kernel.org>
Fixes: c93d8f885809 ("ext4: add basic fs-verity support")
Reported-by: syzbot+9767be679ef5016b6082@syzkaller.appspotmail.com
Signed-off-by: Alexander Potapenko <glider@google.com>
---
 fs/ext4/verity.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ext4/verity.c b/fs/ext4/verity.c
index 3c640bd7ecaeb..30e3b65798b50 100644
--- a/fs/ext4/verity.c
+++ b/fs/ext4/verity.c
@@ -79,7 +79,7 @@ static int pagecache_write(struct inode *inode, const void *buf, size_t count,
 		size_t n = min_t(size_t, count,
 				 PAGE_SIZE - offset_in_page(pos));
 		struct page *page;
-		void *fsdata;
+		void *fsdata = NULL;
 		int res;
 
 		res = aops->write_begin(NULL, mapping, pos, n, &page, &fsdata);
-- 
2.38.1.584.g0f3c55d4c2-goog

[PATCH 2/5] fs: affs: initialize fsdata in affs_truncate()

[Alexander Potapenko]

When aops->write_begin() does not initialize fsdata, KMSAN may report
an error passing the latter to aops->write_end().

Fix this by unconditionally initializing fsdata.

Suggested-by: Eric Biggers <ebiggers@kernel.org>
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Alexander Potapenko <glider@google.com>
---
 fs/affs/file.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/affs/file.c b/fs/affs/file.c
index cefa222f7881c..8daeed31e1af9 100644
--- a/fs/affs/file.c
+++ b/fs/affs/file.c
@@ -880,7 +880,7 @@ affs_truncate(struct inode *inode)
 	if (inode->i_size > AFFS_I(inode)->mmu_private) {
 		struct address_space *mapping = inode->i_mapping;
 		struct page *page;
-		void *fsdata;
+		void *fsdata = NULL;
 		loff_t isize = inode->i_size;
 		int res;
 
-- 
2.38.1.584.g0f3c55d4c2-goog

[PATCH 3/5] fs: f2fs: initialize fsdata in pagecache_write()

[Alexander Potapenko]

When aops->write_begin() does not initialize fsdata, KMSAN may report
an error passing the latter to aops->write_end().

Fix this by unconditionally initializing fsdata.

Suggested-by: Eric Biggers <ebiggers@kernel.org>
Fixes: 95ae251fe828 ("f2fs: add fs-verity support")
Signed-off-by: Alexander Potapenko <glider@google.com>
---
 fs/f2fs/verity.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/f2fs/verity.c b/fs/f2fs/verity.c
index c352fff88a5e6..3f4f3295f1c66 100644
--- a/fs/f2fs/verity.c
+++ b/fs/f2fs/verity.c
@@ -81,7 +81,7 @@ static int pagecache_write(struct inode *inode, const void *buf, size_t count,
 		size_t n = min_t(size_t, count,
 				 PAGE_SIZE - offset_in_page(pos));
 		struct page *page;
-		void *fsdata;
+		void *fsdata = NULL;
 		int res;
 
 		res = aops->write_begin(NULL, mapping, pos, n, &page, &fsdata);
-- 
2.38.1.584.g0f3c55d4c2-goog

[PATCH 4/5] fs: hfs: initialize fsdata in hfs_file_truncate()

[Alexander Potapenko]

When aops->write_begin() does not initialize fsdata, KMSAN may report
an error passing the latter to aops->write_end().

Fix this by unconditionally initializing fsdata.

Suggested-by: Eric Biggers <ebiggers@kernel.org>
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Alexander Potapenko <glider@google.com>
---
 fs/hfs/extent.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/hfs/extent.c b/fs/hfs/extent.c
index 3f7e9bef98743..6d1878b99b305 100644
--- a/fs/hfs/extent.c
+++ b/fs/hfs/extent.c
@@ -486,7 +486,7 @@ void hfs_file_truncate(struct inode *inode)
 		inode->i_size);
 	if (inode->i_size > HFS_I(inode)->phys_size) {
 		struct address_space *mapping = inode->i_mapping;
-		void *fsdata;
+		void *fsdata = NULL;
 		struct page *page;
 
 		/* XXX: Can use generic_cont_expand? */
-- 
2.38.1.584.g0f3c55d4c2-goog

[PATCH 5/5] fs: hfsplus: initialize fsdata in hfsplus_file_truncate()

[Alexander Potapenko]

When aops->write_begin() does not initialize fsdata, KMSAN may report
an error passing the latter to aops->write_end().

Fix this by unconditionally initializing fsdata.

Suggested-by: Eric Biggers <ebiggers@kernel.org>
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Alexander Potapenko <glider@google.com>
---
 fs/hfsplus/extents.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/hfsplus/extents.c b/fs/hfsplus/extents.c
index 721f779b4ec3e..7a542f3dbe502 100644
--- a/fs/hfsplus/extents.c
+++ b/fs/hfsplus/extents.c
@@ -554,7 +554,7 @@ void hfsplus_file_truncate(struct inode *inode)
 	if (inode->i_size > hip->phys_size) {
 		struct address_space *mapping = inode->i_mapping;
 		struct page *page;
-		void *fsdata;
+		void *fsdata = NULL;
 		loff_t size = inode->i_size;
 
 		res = hfsplus_write_begin(NULL, mapping, size, 0,
-- 
2.38.1.584.g0f3c55d4c2-goog

Re: [PATCH 2/5] fs: affs: initialize fsdata in affs_truncate()

[Eric Biggers]

On Mon, Nov 21, 2022 at 12:21:31PM +0100, Alexander Potapenko wrote:
> When aops->write_begin() does not initialize fsdata, KMSAN may report
> an error passing the latter to aops->write_end().
> 
> Fix this by unconditionally initializing fsdata.
> 
> Suggested-by: Eric Biggers <ebiggers@kernel.org>
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")

Are you sure that is the correct Fixes commit?  What about commit f2b6a16eb8f5
("fs: affs convert to new aops")?

- Eric

Re: [PATCH 1/5] fs: ext4: initialize fsdata in pagecache_write()

[Andrew Morton]

On Mon, 21 Nov 2022 12:21:30 +0100 Alexander Potapenko <glider@google.com> wrote:

> When aops->write_begin() does not initialize fsdata, KMSAN reports
> an error passing the latter to aops->write_end().
> 
> Fix this by unconditionally initializing fsdata.
> 
> ...
>

I'm assuming that this is not-a-bug, and that these changes are purely
workarounds for a KMSAN shortcoming?

If true, this important info should be included in each changelog,
please.

If false, please provide a full description of the end-user visible
effects of the bug.

Also, it would be helpful to describe why it is not considered
practical to teach KMSAN to handle this?

> --- a/fs/ext4/verity.c
> +++ b/fs/ext4/verity.c
> @@ -79,7 +79,7 @@ static int pagecache_write(struct inode *inode, const void *buf, size_t count,
>  		size_t n = min_t(size_t, count,
>  				 PAGE_SIZE - offset_in_page(pos));
>  		struct page *page;
> -		void *fsdata;
> +		void *fsdata = NULL;
>  		int res;
>  
>  		res = aops->write_begin(NULL, mapping, pos, n, &page, &fsdata);

Re: [PATCH 1/5] fs: ext4: initialize fsdata in pagecache_write()

[Eric Biggers]

On Mon, Nov 21, 2022 at 12:21:30PM +0100, Alexander Potapenko wrote:
> When aops->write_begin() does not initialize fsdata, KMSAN reports
> an error passing the latter to aops->write_end().
> 
> Fix this by unconditionally initializing fsdata.
> 
> Cc: Eric Biggers <ebiggers@kernel.org>
> Fixes: c93d8f885809 ("ext4: add basic fs-verity support")
> Reported-by: syzbot+9767be679ef5016b6082@syzkaller.appspotmail.com
> Signed-off-by: Alexander Potapenko <glider@google.com>
> ---
>  fs/ext4/verity.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/ext4/verity.c b/fs/ext4/verity.c
> index 3c640bd7ecaeb..30e3b65798b50 100644
> --- a/fs/ext4/verity.c
> +++ b/fs/ext4/verity.c
> @@ -79,7 +79,7 @@ static int pagecache_write(struct inode *inode, const void *buf, size_t count,
>  		size_t n = min_t(size_t, count,
>  				 PAGE_SIZE - offset_in_page(pos));
>  		struct page *page;
> -		void *fsdata;
> +		void *fsdata = NULL;
>  		int res;
>  
>  		res = aops->write_begin(NULL, mapping, pos, n, &page, &fsdata);

Reviewed-by: Eric Biggers <ebiggers@google.com>

- Eric

Re: [PATCH 3/5] fs: f2fs: initialize fsdata in pagecache_write()

[Eric Biggers]

On Mon, Nov 21, 2022 at 12:21:32PM +0100, Alexander Potapenko wrote:
> When aops->write_begin() does not initialize fsdata, KMSAN may report
> an error passing the latter to aops->write_end().
> 
> Fix this by unconditionally initializing fsdata.
> 
> Suggested-by: Eric Biggers <ebiggers@kernel.org>
> Fixes: 95ae251fe828 ("f2fs: add fs-verity support")
> Signed-off-by: Alexander Potapenko <glider@google.com>
> ---
>  fs/f2fs/verity.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/f2fs/verity.c b/fs/f2fs/verity.c
> index c352fff88a5e6..3f4f3295f1c66 100644
> --- a/fs/f2fs/verity.c
> +++ b/fs/f2fs/verity.c
> @@ -81,7 +81,7 @@ static int pagecache_write(struct inode *inode, const void *buf, size_t count,
>  		size_t n = min_t(size_t, count,
>  				 PAGE_SIZE - offset_in_page(pos));
>  		struct page *page;
> -		void *fsdata;
> +		void *fsdata = NULL;
>  		int res;
>  
>  		res = aops->write_begin(NULL, mapping, pos, n, &page, &fsdata);

Reviewed-by: Eric Biggers <ebiggers@google.com>

- Eric

Re: [PATCH 1/5] fs: ext4: initialize fsdata in pagecache_write()

[Matthew Wilcox]

On Mon, Nov 21, 2022 at 11:48:40AM -0800, Andrew Morton wrote:
> On Mon, 21 Nov 2022 12:21:30 +0100 Alexander Potapenko <glider@google.com> wrote:
> 
> > When aops->write_begin() does not initialize fsdata, KMSAN reports
> > an error passing the latter to aops->write_end().
> > 
> > Fix this by unconditionally initializing fsdata.
> > 
> > ...
> >
> 
> I'm assuming that this is not-a-bug, and that these changes are purely
> workarounds for a KMSAN shortcoming?

It's a weird one.  It used to be not-a-bug.  Then we changed from
std=gnu99 to std=gnu11 or something.  And in the intervening years,
the C standards ctte decided that passing an uninitialised pointer to a
function was UB.  So we start by passing a pointer to the pointer to
->write_begin().  Some ->write_begin functions initialise that pointer;
others don't.  Then we pass the pointer directly to ->write_end.  If
->write_begin initialised the pointer, that's fine, and if not, it's UB.
Of course the ->write_end doesn't use it if the ->write_begin didn't
initialise it, but it's too late because merely calling the function
was UB.  Thanks, Itanium!

Re: [PATCH 2/5] fs: affs: initialize fsdata in affs_truncate()

[Alexander Potapenko]

On Mon, Nov 21, 2022 at 8:46 PM Eric Biggers <ebiggers@kernel.org> wrote:
>
> On Mon, Nov 21, 2022 at 12:21:31PM +0100, Alexander Potapenko wrote:
> > When aops->write_begin() does not initialize fsdata, KMSAN may report
> > an error passing the latter to aops->write_end().
> >
> > Fix this by unconditionally initializing fsdata.
> >
> > Suggested-by: Eric Biggers <ebiggers@kernel.org>
> > Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
>
> Are you sure that is the correct Fixes commit?  What about commit f2b6a16eb8f5
> ("fs: affs convert to new aops")?

Hmm, indeed, you are right.

> - Eric



-- 
Alexander Potapenko
Software Engineer

Google Germany GmbH
Erika-Mann-Straße, 33
80636 München

Geschäftsführer: Paul Manicle, Liana Sebastian
Registergericht und -nummer: Hamburg, HRB 86891
Sitz der Gesellschaft: Hamburg

Re: [PATCH 2/5] fs: affs: initialize fsdata in affs_truncate()

[David Sterba]

On Mon, Nov 21, 2022 at 12:21:31PM +0100, Alexander Potapenko wrote:
> When aops->write_begin() does not initialize fsdata, KMSAN may report
> an error passing the latter to aops->write_end().
> 
> Fix this by unconditionally initializing fsdata.
> 
> Suggested-by: Eric Biggers <ebiggers@kernel.org>
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Signed-off-by: Alexander Potapenko <glider@google.com>

With the fixed Fixes: reference,

Acked-by: David Sterba <dsterba@suse.com>

Re: [PATCH 2/5] fs: affs: initialize fsdata in affs_truncate()

[Alexander Potapenko]

On Tue, Nov 22, 2022 at 3:56 PM David Sterba <dsterba@suse.cz> wrote:
>
> On Mon, Nov 21, 2022 at 12:21:31PM +0100, Alexander Potapenko wrote:
> > When aops->write_begin() does not initialize fsdata, KMSAN may report
> > an error passing the latter to aops->write_end().
> >
> > Fix this by unconditionally initializing fsdata.
> >
> > Suggested-by: Eric Biggers <ebiggers@kernel.org>
> > Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> > Signed-off-by: Alexander Potapenko <glider@google.com>
>
> With the fixed Fixes: reference,
>
> Acked-by: David Sterba <dsterba@suse.com>

Hi David,

I've noticed that the ext4 counterpart of this patch is in the
upstream tree already, whereas the affs, f2fs, hfs and hfsplus
versions are not.
Are they picked via a different tree?

Re: [PATCH 2/5] fs: affs: initialize fsdata in affs_truncate()

[David Sterba]

On Tue, Jan 10, 2023 at 01:27:03PM +0100, Alexander Potapenko wrote:
> On Tue, Nov 22, 2022 at 3:56 PM David Sterba <dsterba@suse.cz> wrote:
> >
> > On Mon, Nov 21, 2022 at 12:21:31PM +0100, Alexander Potapenko wrote:
> > > When aops->write_begin() does not initialize fsdata, KMSAN may report
> > > an error passing the latter to aops->write_end().
> > >
> > > Fix this by unconditionally initializing fsdata.
> > >
> > > Suggested-by: Eric Biggers <ebiggers@kernel.org>
> > > Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> > > Signed-off-by: Alexander Potapenko <glider@google.com>
> >
> > With the fixed Fixes: reference,
> >
> > Acked-by: David Sterba <dsterba@suse.com>
> 
> Hi David,
> 
> I've noticed that the ext4 counterpart of this patch is in the
> upstream tree already, whereas the affs, f2fs, hfs and hfsplus
> versions are not.
> Are they picked via a different tree?

I thought it would go in with the rest of the series but it seems that
the patches are meant to be merged independently, so I'll do the affs
part.

Re: [PATCH 2/5] fs: affs: initialize fsdata in affs_truncate()

[Eric Biggers]

On Tue, Jan 10, 2023 at 01:27:03PM +0100, Alexander Potapenko wrote:
> On Tue, Nov 22, 2022 at 3:56 PM David Sterba <dsterba@suse.cz> wrote:
> >
> > On Mon, Nov 21, 2022 at 12:21:31PM +0100, Alexander Potapenko wrote:
> > > When aops->write_begin() does not initialize fsdata, KMSAN may report
> > > an error passing the latter to aops->write_end().
> > >
> > > Fix this by unconditionally initializing fsdata.
> > >
> > > Suggested-by: Eric Biggers <ebiggers@kernel.org>
> > > Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> > > Signed-off-by: Alexander Potapenko <glider@google.com>
> >
> > With the fixed Fixes: reference,
> >
> > Acked-by: David Sterba <dsterba@suse.com>
> 
> Hi David,
> 
> I've noticed that the ext4 counterpart of this patch is in the
> upstream tree already, whereas the affs, f2fs, hfs and hfsplus
> versions are not.
> Are they picked via a different tree?

Generally each filesystem has its own development tree.  All the information is
in MAINTAINERS.  hfs and hfsplus are unmaintained, though.

Maybe try asking Andrew Morton to apply the hfs and hfsplus patches, and any
others that don't get applied, as "maintainer of last resort".

- Eric

Re: [PATCH 3/5] fs: f2fs: initialize fsdata in pagecache_write()

[Eric Biggers]

On Mon, Nov 21, 2022 at 07:53:19PM +0000, Eric Biggers wrote:
> On Mon, Nov 21, 2022 at 12:21:32PM +0100, Alexander Potapenko wrote:
> > When aops->write_begin() does not initialize fsdata, KMSAN may report
> > an error passing the latter to aops->write_end().
> > 
> > Fix this by unconditionally initializing fsdata.
> > 
> > Suggested-by: Eric Biggers <ebiggers@kernel.org>
> > Fixes: 95ae251fe828 ("f2fs: add fs-verity support")
> > Signed-off-by: Alexander Potapenko <glider@google.com>
> > ---
> >  fs/f2fs/verity.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/fs/f2fs/verity.c b/fs/f2fs/verity.c
> > index c352fff88a5e6..3f4f3295f1c66 100644
> > --- a/fs/f2fs/verity.c
> > +++ b/fs/f2fs/verity.c
> > @@ -81,7 +81,7 @@ static int pagecache_write(struct inode *inode, const void *buf, size_t count,
> >  		size_t n = min_t(size_t, count,
> >  				 PAGE_SIZE - offset_in_page(pos));
> >  		struct page *page;
> > -		void *fsdata;
> > +		void *fsdata = NULL;
> >  		int res;
> >  
> >  		res = aops->write_begin(NULL, mapping, pos, n, &page, &fsdata);
> 
> Reviewed-by: Eric Biggers <ebiggers@google.com>
> 

Jaegeuk, can you please apply this patch?

- Eric

Re: [PATCH 4/5] fs: hfs: initialize fsdata in hfs_file_truncate()

[Alexander Potapenko]

On Mon, Nov 21, 2022 at 12:21 PM Alexander Potapenko <glider@google.com> wrote:
>
> When aops->write_begin() does not initialize fsdata, KMSAN may report
> an error passing the latter to aops->write_end().
>
> Fix this by unconditionally initializing fsdata.
>
> Suggested-by: Eric Biggers <ebiggers@kernel.org>
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Signed-off-by: Alexander Potapenko <glider@google.com>

Dear FS maintainers,

HFS/HFSPLUS are orphaned, can someone take this patch to their tree?
Thanks in advance!
(same for "fs: hfsplus: initialize fsdata in hfsplus_file_truncate()":
https://lore.kernel.org/all/20221121112134.407362-5-glider@google.com/)

Re: [PATCH 4/5] fs: hfs: initialize fsdata in hfs_file_truncate()

[Andrew Morton]

On Tue, 24 Jan 2023 11:51:30 +0100 Alexander Potapenko <glider@google.com> wrote:

> On Mon, Nov 21, 2022 at 12:21 PM Alexander Potapenko <glider@google.com> wrote:
> >
> > When aops->write_begin() does not initialize fsdata, KMSAN may report
> > an error passing the latter to aops->write_end().
> >
> > Fix this by unconditionally initializing fsdata.
> >
> > Suggested-by: Eric Biggers <ebiggers@kernel.org>
> > Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> > Signed-off-by: Alexander Potapenko <glider@google.com>
> 
> Dear FS maintainers,
> 
> HFS/HFSPLUS are orphaned, can someone take this patch to their tree?
> Thanks in advance!
> (same for "fs: hfsplus: initialize fsdata in hfsplus_file_truncate()":
> https://lore.kernel.org/all/20221121112134.407362-5-glider@google.com/)

I grabbed both.

I removed the

	Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")

because that might provoke the backport bots to backport this fix
across eight years worth of kernels.  Before KMSAN existed!

If you intended that this be backported then please let's come up with a
more precise Fixes: target and we'll add cc:stable.

Re: [PATCH 4/5] fs: hfs: initialize fsdata in hfs_file_truncate()

[Alexander Potapenko]

On Tue, Jan 24, 2023 at 10:04 PM Andrew Morton
<akpm@linux-foundation.org> wrote:
>
> On Tue, 24 Jan 2023 11:51:30 +0100 Alexander Potapenko <glider@google.com> wrote:
>
> > On Mon, Nov 21, 2022 at 12:21 PM Alexander Potapenko <glider@google.com> wrote:
> > >
> > > When aops->write_begin() does not initialize fsdata, KMSAN may report
> > > an error passing the latter to aops->write_end().
> > >
> > > Fix this by unconditionally initializing fsdata.
> > >
> > > Suggested-by: Eric Biggers <ebiggers@kernel.org>
> > > Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> > > Signed-off-by: Alexander Potapenko <glider@google.com>
> >
> > Dear FS maintainers,
> >
> > HFS/HFSPLUS are orphaned, can someone take this patch to their tree?
> > Thanks in advance!
> > (same for "fs: hfsplus: initialize fsdata in hfsplus_file_truncate()":
> > https://lore.kernel.org/all/20221121112134.407362-5-glider@google.com/)
>
> I grabbed both.
>
> I removed the
>
>         Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
>
> because that might provoke the backport bots to backport this fix
> across eight years worth of kernels.  Before KMSAN existed!

Right, makes sense.

Re: [PATCH 3/5] fs: f2fs: initialize fsdata in pagecache_write()

[Jaegeuk Kim]

On 01/22, Eric Biggers wrote:
> On Mon, Nov 21, 2022 at 07:53:19PM +0000, Eric Biggers wrote:
> > On Mon, Nov 21, 2022 at 12:21:32PM +0100, Alexander Potapenko wrote:
> > > When aops->write_begin() does not initialize fsdata, KMSAN may report
> > > an error passing the latter to aops->write_end().
> > > 
> > > Fix this by unconditionally initializing fsdata.
> > > 
> > > Suggested-by: Eric Biggers <ebiggers@kernel.org>
> > > Fixes: 95ae251fe828 ("f2fs: add fs-verity support")
> > > Signed-off-by: Alexander Potapenko <glider@google.com>
> > > ---
> > >  fs/f2fs/verity.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > diff --git a/fs/f2fs/verity.c b/fs/f2fs/verity.c
> > > index c352fff88a5e6..3f4f3295f1c66 100644
> > > --- a/fs/f2fs/verity.c
> > > +++ b/fs/f2fs/verity.c
> > > @@ -81,7 +81,7 @@ static int pagecache_write(struct inode *inode, const void *buf, size_t count,
> > >  		size_t n = min_t(size_t, count,
> > >  				 PAGE_SIZE - offset_in_page(pos));
> > >  		struct page *page;
> > > -		void *fsdata;
> > > +		void *fsdata = NULL;
> > >  		int res;
> > >  
> > >  		res = aops->write_begin(NULL, mapping, pos, n, &page, &fsdata);
> > 
> > Reviewed-by: Eric Biggers <ebiggers@google.com>
> > 
> 
> Jaegeuk, can you please apply this patch?

Yup, applied.

> 
> - Eric