From: Pankaj Raghav <p.raghav@samsung.com>
iomap_dio_zero() will pad a fs block with zeroes if the direct IO size
< fs block size. iomap_dio_zero() has an implicit assumption that fs block
size < page_size. This is true for most filesystems at the moment.
If the block size > page size, this will send the contents of the page
next to zero page(as len > PAGE_SIZE) to the underlying block device,
causing FS corruption.
iomap is a generic infrastructure and it should not make any assumptions
about the fs block size and the page size of the system.
Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>
---
fs/iomap/buffered-io.c | 4 ++--
fs/iomap/direct-io.c | 45 ++++++++++++++++++++++++++++++++++++------
2 files changed, 41 insertions(+), 8 deletions(-)
diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index f420c53d86acc..d745f718bcde8 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -2007,10 +2007,10 @@ iomap_writepages(struct address_space *mapping, struct writeback_control *wbc,
}
EXPORT_SYMBOL_GPL(iomap_writepages);
-static int __init iomap_init(void)
+static int __init iomap_buffered_init(void)
{
return bioset_init(&iomap_ioend_bioset, 4 * (PAGE_SIZE / SECTOR_SIZE),
offsetof(struct iomap_ioend, io_bio),
BIOSET_NEED_BVECS);
}
-fs_initcall(iomap_init);
+fs_initcall(iomap_buffered_init);
diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
index f3b43d223a46e..c02b266bba525 100644
--- a/fs/iomap/direct-io.c
+++ b/fs/iomap/direct-io.c
@@ -11,6 +11,7 @@
#include <linux/iomap.h>
#include <linux/backing-dev.h>
#include <linux/uio.h>
+#include <linux/set_memory.h>
#include <linux/task_io_accounting_ops.h>
#include "trace.h"
@@ -27,6 +28,13 @@
#define IOMAP_DIO_WRITE (1U << 30)
#define IOMAP_DIO_DIRTY (1U << 31)
+/*
+ * Used for sub block zeroing in iomap_dio_zero()
+ */
+#define IOMAP_ZERO_PAGE_SIZE (SZ_64K)
+#define IOMAP_ZERO_PAGE_ORDER (get_order(IOMAP_ZERO_PAGE_SIZE))
+static struct page *zero_page;
+
struct iomap_dio {
struct kiocb *iocb;
const struct iomap_dio_ops *dops;
@@ -232,13 +240,20 @@ void iomap_dio_bio_end_io(struct bio *bio)
}
EXPORT_SYMBOL_GPL(iomap_dio_bio_end_io);
-static void iomap_dio_zero(const struct iomap_iter *iter, struct iomap_dio *dio,
+static int iomap_dio_zero(const struct iomap_iter *iter, struct iomap_dio *dio,
loff_t pos, unsigned len)
{
struct inode *inode = file_inode(dio->iocb->ki_filp);
- struct page *page = ZERO_PAGE(0);
struct bio *bio;
+ if (!len)
+ return 0;
+ /*
+ * Max block size supported is 64k
+ */
+ if (WARN_ON_ONCE(len > IOMAP_ZERO_PAGE_SIZE))
+ return -EINVAL;
+
bio = iomap_dio_alloc_bio(iter, dio, 1, REQ_OP_WRITE | REQ_SYNC | REQ_IDLE);
fscrypt_set_bio_crypt_ctx(bio, inode, pos >> inode->i_blkbits,
GFP_KERNEL);
@@ -246,8 +261,9 @@ static void iomap_dio_zero(const struct iomap_iter *iter, struct iomap_dio *dio,
bio->bi_private = dio;
bio->bi_end_io = iomap_dio_bio_end_io;
- __bio_add_page(bio, page, len, 0);
+ __bio_add_page(bio, zero_page, len, 0);
iomap_dio_submit_bio(iter, dio, bio, pos);
+ return 0;
}
/*
@@ -356,8 +372,10 @@ static loff_t iomap_dio_bio_iter(const struct iomap_iter *iter,
if (need_zeroout) {
/* zero out from the start of the block to the write offset */
pad = pos & (fs_block_size - 1);
- if (pad)
- iomap_dio_zero(iter, dio, pos - pad, pad);
+
+ ret = iomap_dio_zero(iter, dio, pos - pad, pad);
+ if (ret)
+ goto out;
}
/*
@@ -431,7 +449,8 @@ static loff_t iomap_dio_bio_iter(const struct iomap_iter *iter,
/* zero out from the end of the write to the end of the block */
pad = pos & (fs_block_size - 1);
if (pad)
- iomap_dio_zero(iter, dio, pos, fs_block_size - pad);
+ ret = iomap_dio_zero(iter, dio, pos,
+ fs_block_size - pad);
}
out:
/* Undo iter limitation to current extent */
@@ -753,3 +772,17 @@ iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
return iomap_dio_complete(dio);
}
EXPORT_SYMBOL_GPL(iomap_dio_rw);
+
+static int __init iomap_dio_init(void)
+{
+ zero_page = alloc_pages(GFP_KERNEL | __GFP_ZERO,
+ IOMAP_ZERO_PAGE_ORDER);
+
+ if (!zero_page)
+ return -ENOMEM;
+
+ set_memory_ro((unsigned long)page_address(zero_page),
+ 1U << IOMAP_ZERO_PAGE_ORDER);
+ return 0;
+}
+fs_initcall(iomap_dio_init);
--
2.44.1On Thu, Jul 04, 2024 at 11:23:16AM +0000, Pankaj Raghav (Samsung) wrote: > From: Pankaj Raghav <p.raghav@samsung.com> > > iomap_dio_zero() will pad a fs block with zeroes if the direct IO size > < fs block size. iomap_dio_zero() has an implicit assumption that fs block > size < page_size. This is true for most filesystems at the moment. > > If the block size > page size, this will send the contents of the page > next to zero page(as len > PAGE_SIZE) to the underlying block device, > causing FS corruption. > > iomap is a generic infrastructure and it should not make any assumptions > about the fs block size and the page size of the system. > > Signed-off-by: Pankaj Raghav <p.raghav@samsung.com> > --- > fs/iomap/buffered-io.c | 4 ++-- > fs/iomap/direct-io.c | 45 ++++++++++++++++++++++++++++++++++++------ > 2 files changed, 41 insertions(+), 8 deletions(-) Looks fine. Reviewed-by: Dave Chinner <dchinner@redhat.com> -- Dave Chinner david@fromorbit.com
On Thu, Jul 04, 2024 at 11:23:16AM +0000, Pankaj Raghav (Samsung) wrote:
> From: Pankaj Raghav <p.raghav@samsung.com>
>
> iomap_dio_zero() will pad a fs block with zeroes if the direct IO size
> < fs block size. iomap_dio_zero() has an implicit assumption that fs block
> size < page_size. This is true for most filesystems at the moment.
>
> If the block size > page size, this will send the contents of the page
> next to zero page(as len > PAGE_SIZE) to the underlying block device,
> causing FS corruption.
>
> iomap is a generic infrastructure and it should not make any assumptions
> about the fs block size and the page size of the system.
>
> Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>
> ---
> fs/iomap/buffered-io.c | 4 ++--
> fs/iomap/direct-io.c | 45 ++++++++++++++++++++++++++++++++++++------
> 2 files changed, 41 insertions(+), 8 deletions(-)
>
> diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> index f420c53d86acc..d745f718bcde8 100644
> --- a/fs/iomap/buffered-io.c
> +++ b/fs/iomap/buffered-io.c
> @@ -2007,10 +2007,10 @@ iomap_writepages(struct address_space *mapping, struct writeback_control *wbc,
> }
> EXPORT_SYMBOL_GPL(iomap_writepages);
>
> -static int __init iomap_init(void)
> +static int __init iomap_buffered_init(void)
> {
> return bioset_init(&iomap_ioend_bioset, 4 * (PAGE_SIZE / SECTOR_SIZE),
> offsetof(struct iomap_ioend, io_bio),
> BIOSET_NEED_BVECS);
> }
> -fs_initcall(iomap_init);
> +fs_initcall(iomap_buffered_init);
> diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
> index f3b43d223a46e..c02b266bba525 100644
> --- a/fs/iomap/direct-io.c
> +++ b/fs/iomap/direct-io.c
> @@ -11,6 +11,7 @@
> #include <linux/iomap.h>
> #include <linux/backing-dev.h>
> #include <linux/uio.h>
> +#include <linux/set_memory.h>
> #include <linux/task_io_accounting_ops.h>
> #include "trace.h"
>
> @@ -27,6 +28,13 @@
> #define IOMAP_DIO_WRITE (1U << 30)
> #define IOMAP_DIO_DIRTY (1U << 31)
>
> +/*
> + * Used for sub block zeroing in iomap_dio_zero()
> + */
> +#define IOMAP_ZERO_PAGE_SIZE (SZ_64K)
> +#define IOMAP_ZERO_PAGE_ORDER (get_order(IOMAP_ZERO_PAGE_SIZE))
> +static struct page *zero_page;
> +
> struct iomap_dio {
> struct kiocb *iocb;
> const struct iomap_dio_ops *dops;
> @@ -232,13 +240,20 @@ void iomap_dio_bio_end_io(struct bio *bio)
> }
> EXPORT_SYMBOL_GPL(iomap_dio_bio_end_io);
>
> -static void iomap_dio_zero(const struct iomap_iter *iter, struct iomap_dio *dio,
> +static int iomap_dio_zero(const struct iomap_iter *iter, struct iomap_dio *dio,
> loff_t pos, unsigned len)
> {
> struct inode *inode = file_inode(dio->iocb->ki_filp);
> - struct page *page = ZERO_PAGE(0);
> struct bio *bio;
>
> + if (!len)
> + return 0;
> + /*
> + * Max block size supported is 64k
> + */
> + if (WARN_ON_ONCE(len > IOMAP_ZERO_PAGE_SIZE))
> + return -EINVAL;
> +
> bio = iomap_dio_alloc_bio(iter, dio, 1, REQ_OP_WRITE | REQ_SYNC | REQ_IDLE);
> fscrypt_set_bio_crypt_ctx(bio, inode, pos >> inode->i_blkbits,
> GFP_KERNEL);
> @@ -246,8 +261,9 @@ static void iomap_dio_zero(const struct iomap_iter *iter, struct iomap_dio *dio,
> bio->bi_private = dio;
> bio->bi_end_io = iomap_dio_bio_end_io;
>
> - __bio_add_page(bio, page, len, 0);
> + __bio_add_page(bio, zero_page, len, 0);
> iomap_dio_submit_bio(iter, dio, bio, pos);
> + return 0;
> }
>
> /*
> @@ -356,8 +372,10 @@ static loff_t iomap_dio_bio_iter(const struct iomap_iter *iter,
> if (need_zeroout) {
> /* zero out from the start of the block to the write offset */
> pad = pos & (fs_block_size - 1);
> - if (pad)
> - iomap_dio_zero(iter, dio, pos - pad, pad);
> +
> + ret = iomap_dio_zero(iter, dio, pos - pad, pad);
> + if (ret)
> + goto out;
> }
>
> /*
> @@ -431,7 +449,8 @@ static loff_t iomap_dio_bio_iter(const struct iomap_iter *iter,
> /* zero out from the end of the write to the end of the block */
> pad = pos & (fs_block_size - 1);
> if (pad)
> - iomap_dio_zero(iter, dio, pos, fs_block_size - pad);
> + ret = iomap_dio_zero(iter, dio, pos,
> + fs_block_size - pad);
> }
> out:
> /* Undo iter limitation to current extent */
> @@ -753,3 +772,17 @@ iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
> return iomap_dio_complete(dio);
> }
> EXPORT_SYMBOL_GPL(iomap_dio_rw);
> +
> +static int __init iomap_dio_init(void)
> +{
> + zero_page = alloc_pages(GFP_KERNEL | __GFP_ZERO,
> + IOMAP_ZERO_PAGE_ORDER);
> +
> + if (!zero_page)
> + return -ENOMEM;
> +
> + set_memory_ro((unsigned long)page_address(zero_page),
> + 1U << IOMAP_ZERO_PAGE_ORDER);
> + return 0;
> +}
> +fs_initcall(iomap_dio_init);
This ^^^ could be refactored into a zeropage.ko module some day as a
separate patch to amortize the cost of the 64k buffer that never goes
away.
This patch looks ok though, so:
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
--D
> --
> 2.44.1
>
>
On 7/4/24 13:23, Pankaj Raghav (Samsung) wrote:
> From: Pankaj Raghav <p.raghav@samsung.com>
>
> iomap_dio_zero() will pad a fs block with zeroes if the direct IO size
> < fs block size. iomap_dio_zero() has an implicit assumption that fs block
> size < page_size. This is true for most filesystems at the moment.
>
> If the block size > page size, this will send the contents of the page
> next to zero page(as len > PAGE_SIZE) to the underlying block device,
> causing FS corruption.
>
> iomap is a generic infrastructure and it should not make any assumptions
> about the fs block size and the page size of the system.
>
> Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>
> ---
> fs/iomap/buffered-io.c | 4 ++--
> fs/iomap/direct-io.c | 45 ++++++++++++++++++++++++++++++++++++------
> 2 files changed, 41 insertions(+), 8 deletions(-)
>
> diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> index f420c53d86acc..d745f718bcde8 100644
> --- a/fs/iomap/buffered-io.c
> +++ b/fs/iomap/buffered-io.c
> @@ -2007,10 +2007,10 @@ iomap_writepages(struct address_space *mapping, struct writeback_control *wbc,
> }
> EXPORT_SYMBOL_GPL(iomap_writepages);
>
> -static int __init iomap_init(void)
> +static int __init iomap_buffered_init(void)
> {
> return bioset_init(&iomap_ioend_bioset, 4 * (PAGE_SIZE / SECTOR_SIZE),
> offsetof(struct iomap_ioend, io_bio),
> BIOSET_NEED_BVECS);
> }
> -fs_initcall(iomap_init);
> +fs_initcall(iomap_buffered_init);
> diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
> index f3b43d223a46e..c02b266bba525 100644
> --- a/fs/iomap/direct-io.c
> +++ b/fs/iomap/direct-io.c
> @@ -11,6 +11,7 @@
> #include <linux/iomap.h>
> #include <linux/backing-dev.h>
> #include <linux/uio.h>
> +#include <linux/set_memory.h>
> #include <linux/task_io_accounting_ops.h>
> #include "trace.h"
>
> @@ -27,6 +28,13 @@
> #define IOMAP_DIO_WRITE (1U << 30)
> #define IOMAP_DIO_DIRTY (1U << 31)
>
> +/*
> + * Used for sub block zeroing in iomap_dio_zero()
> + */
> +#define IOMAP_ZERO_PAGE_SIZE (SZ_64K)
> +#define IOMAP_ZERO_PAGE_ORDER (get_order(IOMAP_ZERO_PAGE_SIZE))
> +static struct page *zero_page;
> +
There are other users of ZERO_PAGE, most notably in fs/direct-io.c and
block/blk-lib.c. Any chance to make this available to them?
Cheers,
Hannes
--
Dr. Hannes Reinecke Kernel Storage Architect
hare@suse.de +49 911 74053 688
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. Knoblich
On Thu, Jul 04, 2024 at 05:37:32PM +0200, Hannes Reinecke wrote:
> On 7/4/24 13:23, Pankaj Raghav (Samsung) wrote:
> > From: Pankaj Raghav <p.raghav@samsung.com>
> >
> > iomap_dio_zero() will pad a fs block with zeroes if the direct IO size
> > < fs block size. iomap_dio_zero() has an implicit assumption that fs block
> > size < page_size. This is true for most filesystems at the moment.
> >
> > If the block size > page size, this will send the contents of the page
> > next to zero page(as len > PAGE_SIZE) to the underlying block device,
> > causing FS corruption.
> >
> > iomap is a generic infrastructure and it should not make any assumptions
> > about the fs block size and the page size of the system.
> >
> > Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>
> > ---
> > fs/iomap/buffered-io.c | 4 ++--
> > fs/iomap/direct-io.c | 45 ++++++++++++++++++++++++++++++++++++------
> > 2 files changed, 41 insertions(+), 8 deletions(-)
> >
> > diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> > index f420c53d86acc..d745f718bcde8 100644
> > --- a/fs/iomap/buffered-io.c
> > +++ b/fs/iomap/buffered-io.c
> > @@ -2007,10 +2007,10 @@ iomap_writepages(struct address_space *mapping, struct writeback_control *wbc,
> > }
> > EXPORT_SYMBOL_GPL(iomap_writepages);
> > -static int __init iomap_init(void)
> > +static int __init iomap_buffered_init(void)
> > {
> > return bioset_init(&iomap_ioend_bioset, 4 * (PAGE_SIZE / SECTOR_SIZE),
> > offsetof(struct iomap_ioend, io_bio),
> > BIOSET_NEED_BVECS);
> > }
> > -fs_initcall(iomap_init);
> > +fs_initcall(iomap_buffered_init);
> > diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
> > index f3b43d223a46e..c02b266bba525 100644
> > --- a/fs/iomap/direct-io.c
> > +++ b/fs/iomap/direct-io.c
> > @@ -11,6 +11,7 @@
> > #include <linux/iomap.h>
> > #include <linux/backing-dev.h>
> > #include <linux/uio.h>
> > +#include <linux/set_memory.h>
> > #include <linux/task_io_accounting_ops.h>
> > #include "trace.h"
> > @@ -27,6 +28,13 @@
> > #define IOMAP_DIO_WRITE (1U << 30)
> > #define IOMAP_DIO_DIRTY (1U << 31)
> > +/*
> > + * Used for sub block zeroing in iomap_dio_zero()
> > + */
> > +#define IOMAP_ZERO_PAGE_SIZE (SZ_64K)
> > +#define IOMAP_ZERO_PAGE_ORDER (get_order(IOMAP_ZERO_PAGE_SIZE))
> > +static struct page *zero_page;
> > +
>
> There are other users of ZERO_PAGE, most notably in fs/direct-io.c and
> block/blk-lib.c. Any chance to make this available to them?
Please, no.
We need to stop feature creeping this patchset and bring it to a
close. If changing code entirely unrelated to this patchset is
desired, please do it as a separate independent set of patches.
-Dave.
--
Dave Chinner
david@fromorbit.com
On 7/5/24 00:13, Dave Chinner wrote:
> On Thu, Jul 04, 2024 at 05:37:32PM +0200, Hannes Reinecke wrote:
>> On 7/4/24 13:23, Pankaj Raghav (Samsung) wrote:
>>> From: Pankaj Raghav <p.raghav@samsung.com>
>>>
>>> iomap_dio_zero() will pad a fs block with zeroes if the direct IO size
>>> < fs block size. iomap_dio_zero() has an implicit assumption that fs block
>>> size < page_size. This is true for most filesystems at the moment.
>>>
>>> If the block size > page size, this will send the contents of the page
>>> next to zero page(as len > PAGE_SIZE) to the underlying block device,
>>> causing FS corruption.
>>>
>>> iomap is a generic infrastructure and it should not make any assumptions
>>> about the fs block size and the page size of the system.
>>>
>>> Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>
>>> ---
>>> fs/iomap/buffered-io.c | 4 ++--
>>> fs/iomap/direct-io.c | 45 ++++++++++++++++++++++++++++++++++++------
>>> 2 files changed, 41 insertions(+), 8 deletions(-)
>>>
>>> diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
>>> index f420c53d86acc..d745f718bcde8 100644
>>> --- a/fs/iomap/buffered-io.c
>>> +++ b/fs/iomap/buffered-io.c
>>> @@ -2007,10 +2007,10 @@ iomap_writepages(struct address_space *mapping, struct writeback_control *wbc,
>>> }
>>> EXPORT_SYMBOL_GPL(iomap_writepages);
>>> -static int __init iomap_init(void)
>>> +static int __init iomap_buffered_init(void)
>>> {
>>> return bioset_init(&iomap_ioend_bioset, 4 * (PAGE_SIZE / SECTOR_SIZE),
>>> offsetof(struct iomap_ioend, io_bio),
>>> BIOSET_NEED_BVECS);
>>> }
>>> -fs_initcall(iomap_init);
>>> +fs_initcall(iomap_buffered_init);
>>> diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
>>> index f3b43d223a46e..c02b266bba525 100644
>>> --- a/fs/iomap/direct-io.c
>>> +++ b/fs/iomap/direct-io.c
>>> @@ -11,6 +11,7 @@
>>> #include <linux/iomap.h>
>>> #include <linux/backing-dev.h>
>>> #include <linux/uio.h>
>>> +#include <linux/set_memory.h>
>>> #include <linux/task_io_accounting_ops.h>
>>> #include "trace.h"
>>> @@ -27,6 +28,13 @@
>>> #define IOMAP_DIO_WRITE (1U << 30)
>>> #define IOMAP_DIO_DIRTY (1U << 31)
>>> +/*
>>> + * Used for sub block zeroing in iomap_dio_zero()
>>> + */
>>> +#define IOMAP_ZERO_PAGE_SIZE (SZ_64K)
>>> +#define IOMAP_ZERO_PAGE_ORDER (get_order(IOMAP_ZERO_PAGE_SIZE))
>>> +static struct page *zero_page;
>>> +
>>
>> There are other users of ZERO_PAGE, most notably in fs/direct-io.c and
>> block/blk-lib.c. Any chance to make this available to them?
>
> Please, no.
>
> We need to stop feature creeping this patchset and bring it to a
> close. If changing code entirely unrelated to this patchset is
> desired, please do it as a separate independent set of patches.
>
Agree; it was a suggestion only.
Pankaj, you can add my:
Reviewed-by: Hannes Reinecke <hare@suse.de>
Cheers,
Hannes
--
Dr. Hannes Reinecke Kernel Storage Architect
hare@suse.de +49 911 74053 688
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. Knoblich
> > > > > > There are other users of ZERO_PAGE, most notably in fs/direct-io.c and > > > block/blk-lib.c. Any chance to make this available to them? > > > > Please, no. > > > > We need to stop feature creeping this patchset and bring it to a > > close. If changing code entirely unrelated to this patchset is > > desired, please do it as a separate independent set of patches. > > > Agree; it was a suggestion only. I was going to say the same thing that Dave said as well as we are almost there with this series :) But I will add your suggestion in my TODO. It would be good to have some common infra to avoid allocating larger zero pages all over the place. > > Pankaj, you can add my: > > Reviewed-by: Hannes Reinecke <hare@suse.de> Thanks Hannes.
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