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[PATCH] zram: fix partial I/O config check

Jianyue Wu posted 1 patch 1 week ago 
drivers/block/zram/zram_drv.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
[PATCH] zram: fix partial I/O config check
Posted by Jianyue Wu 1 week ago 
IS_ENABLED() expects a CONFIG_* symbol. Use the real Kconfig symbol so
this warning reflects whether synchronous partial I/O is built in.

Signed-off-by: Jianyue Wu <wujianyue000@gmail.com>
---
zram: fix partial I/O config check
---
 drivers/block/zram/zram_drv.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 6e1330ce4bc1..72f89fd5572e 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -1510,7 +1510,7 @@ static int read_from_bdev(struct zram *zram, struct page *page, u32 index,
 {
 	atomic64_inc(&zram->stats.bd_reads);
 	if (!parent) {
-		if (WARN_ON_ONCE(!IS_ENABLED(ZRAM_PARTIAL_IO)))
+		if (WARN_ON_ONCE(!IS_ENABLED(CONFIG_ZRAM_PARTIAL_IO)))
 			return -EIO;
 		return read_from_bdev_sync(zram, page, index, blk_idx);
 	}

---
base-commit: 404fb4f38e8f38469dfff4df0205c9d18eeb1f57
change-id: 20260531-zram-fix-partial-io-config-check-on-akpm-c62b972416f8

Best regards,
-- 
Jianyue Wu <wujianyue000@gmail.com>
Re: [PATCH] zram: fix partial I/O config check
Posted by Barry Song 1 week ago 
On Sun, May 31, 2026 at 8:35 PM Jianyue Wu <wujianyue000@gmail.com> wrote:
>
> IS_ENABLED() expects a CONFIG_* symbol. Use the real Kconfig symbol so
> this warning reflects whether synchronous partial I/O is built in.
>
> Signed-off-by: Jianyue Wu <wujianyue000@gmail.com>
> ---
> zram: fix partial I/O config check
> ---
>  drivers/block/zram/zram_drv.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> index 6e1330ce4bc1..72f89fd5572e 100644
> --- a/drivers/block/zram/zram_drv.c
> +++ b/drivers/block/zram/zram_drv.c
> @@ -1510,7 +1510,7 @@ static int read_from_bdev(struct zram *zram, struct page *page, u32 index,
>  {
>         atomic64_inc(&zram->stats.bd_reads);
>         if (!parent) {
> -               if (WARN_ON_ONCE(!IS_ENABLED(ZRAM_PARTIAL_IO)))
> +               if (WARN_ON_ONCE(!IS_ENABLED(CONFIG_ZRAM_PARTIAL_IO)))

However, I don't see ZRAM_PARTIAL_IO defined as a Kconfig option.

#if PAGE_SIZE != 4096
static inline bool is_partial_io(struct bio_vec *bvec)
{
        return bvec->bv_len != PAGE_SIZE;
}
#define ZRAM_PARTIAL_IO         1
#else
static inline bool is_partial_io(struct bio_vec *bvec)
{
        return false;
}
#endif


>                         return -EIO;
>                 return read_from_bdev_sync(zram, page, index, blk_idx);
>         }
>
> ---
> base-commit: 404fb4f38e8f38469dfff4df0205c9d18eeb1f57
> change-id: 20260531-zram-fix-partial-io-config-check-on-akpm-c62b972416f8
>
> Best regards,
> --
> Jianyue Wu <wujianyue000@gmail.com>
>
Re: [PATCH] zram: fix partial I/O config check
Posted by Jianyue Wu 1 week ago 
On Mon, Jun 1, 2026 at 5:38 AM Barry Song <baohua@kernel.org> wrote:
> > diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> > index 6e1330ce4bc1..72f89fd5572e 100644
> > --- a/drivers/block/zram/zram_drv.c
> > +++ b/drivers/block/zram/zram_drv.c
> > @@ -1510,7 +1510,7 @@ static int read_from_bdev(struct zram *zram, struct page *page, u32 index,
> >  {
> >         atomic64_inc(&zram->stats.bd_reads);
> >         if (!parent) {
> > -               if (WARN_ON_ONCE(!IS_ENABLED(ZRAM_PARTIAL_IO)))
> > +               if (WARN_ON_ONCE(!IS_ENABLED(CONFIG_ZRAM_PARTIAL_IO)))
>
> However, I don't see ZRAM_PARTIAL_IO defined as a Kconfig option.

You are right. ZRAM_PARTIAL_IO is a local source-level define, not a
Kconfig symbol.

Please drop this patch.
Sorry for the noise.

Thanks,
Jianyue
Re: [PATCH] zram: fix partial I/O config check
Posted by Baoquan He 1 week ago 
On 06/01/26 at 08:25am, Jianyue Wu wrote:
> On Mon, Jun 1, 2026 at 5:38 AM Barry Song <baohua@kernel.org> wrote:
> > > diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> > > index 6e1330ce4bc1..72f89fd5572e 100644
> > > --- a/drivers/block/zram/zram_drv.c
> > > +++ b/drivers/block/zram/zram_drv.c
> > > @@ -1510,7 +1510,7 @@ static int read_from_bdev(struct zram *zram, struct page *page, u32 index,
> > >  {
> > >         atomic64_inc(&zram->stats.bd_reads);
> > >         if (!parent) {
> > > -               if (WARN_ON_ONCE(!IS_ENABLED(ZRAM_PARTIAL_IO)))
> > > +               if (WARN_ON_ONCE(!IS_ENABLED(CONFIG_ZRAM_PARTIAL_IO)))
> >
> > However, I don't see ZRAM_PARTIAL_IO defined as a Kconfig option.
> 
> You are right. ZRAM_PARTIAL_IO is a local source-level define, not a
> Kconfig symbol.


How about removing ZRAM_PARTIAL_IO and use PAGE_SIZE to check?

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 07111455eecf..ca0c29482283 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -221,7 +221,6 @@ static inline bool is_partial_io(struct bio_vec *bvec)
 {
 	return bvec->bv_len != PAGE_SIZE;
 }
-#define ZRAM_PARTIAL_IO		1
 #else
 static inline bool is_partial_io(struct bio_vec *bvec)
 {
@@ -1507,7 +1506,7 @@ static int read_from_bdev(struct zram *zram, struct page *page, u32 index,
 {
 	atomic64_inc(&zram->stats.bd_reads);
 	if (!parent) {
-		if (WARN_ON_ONCE(!IS_ENABLED(ZRAM_PARTIAL_IO)))
+		if (WARN_ON_ONCE(PAGE_SIZE == 4096))
 			return -EIO;
 		return read_from_bdev_sync(zram, page, index, blk_idx);
 	}
Re: [PATCH] zram: fix partial I/O config check
Posted by Jianyue Wu 1 week ago 
On Mon, Jun 1, 2026 at 8:44 AM Baoquan He <baoquan.he@linux.dev> wrote:
>
> On 06/01/26 at 08:25am, Jianyue Wu wrote:
> > On Mon, Jun 1, 2026 at 5:38 AM Barry Song <baohua@kernel.org> wrote:
> > > > diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> > > > index 6e1330ce4bc1..72f89fd5572e 100644
> > > > --- a/drivers/block/zram/zram_drv.c
> > > > +++ b/drivers/block/zram/zram_drv.c
> > > > @@ -1510,7 +1510,7 @@ static int read_from_bdev(struct zram *zram, struct page *page, u32 index,
> > > >  {
> > > >         atomic64_inc(&zram->stats.bd_reads);
> > > >         if (!parent) {
> > > > -               if (WARN_ON_ONCE(!IS_ENABLED(ZRAM_PARTIAL_IO)))
> > > > +               if (WARN_ON_ONCE(!IS_ENABLED(CONFIG_ZRAM_PARTIAL_IO)))
> > >
> > > However, I don't see ZRAM_PARTIAL_IO defined as a Kconfig option.
> >
> > You are right. ZRAM_PARTIAL_IO is a local source-level define, not a
> > Kconfig symbol.
>
>
> How about removing ZRAM_PARTIAL_IO and use PAGE_SIZE to check?
>
> diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> index 07111455eecf..ca0c29482283 100644
> --- a/drivers/block/zram/zram_drv.c
> +++ b/drivers/block/zram/zram_drv.c
> @@ -221,7 +221,6 @@ static inline bool is_partial_io(struct bio_vec *bvec)
>  {
>         return bvec->bv_len != PAGE_SIZE;
>  }
> -#define ZRAM_PARTIAL_IO                1
>  #else
>  static inline bool is_partial_io(struct bio_vec *bvec)
>  {
> @@ -1507,7 +1506,7 @@ static int read_from_bdev(struct zram *zram, struct page *page, u32 index,
>  {
>         atomic64_inc(&zram->stats.bd_reads);
>         if (!parent) {
> -               if (WARN_ON_ONCE(!IS_ENABLED(ZRAM_PARTIAL_IO)))
> +               if (WARN_ON_ONCE(PAGE_SIZE == 4096))
>                         return -EIO;
>                 return read_from_bdev_sync(zram, page, index, blk_idx);
>         }
>

Yes, that looks good. Thanks for the patch.
The synchronous backing-device read is only needed on PAGE_SIZE != 4096
systems, where partial I/O can happen. On 4K systems is_partial_io()
always returns false, so this path should not be hit in normal operation.

Thanks,
Jianyue

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