[f2fs-dev] [PATCH] f2fs: do not support mmap write for large folio

[f2fs-dev] [PATCH] f2fs: do not support mmap write for large folio

[Jaegeuk Kim via Linux-f2fs-devel]

Let's check mmmap writes onto the large folio.

Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
---
 fs/f2fs/file.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 2c4880f24b54..edfc3a374c40 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -82,7 +82,7 @@ static vm_fault_t f2fs_vm_page_mkwrite(struct vm_fault *vmf)
 	int err = 0;
 	vm_fault_t ret;
 
-	if (unlikely(IS_IMMUTABLE(inode)))
+	if (mapping_large_folio_support(inode->i_mapping))
 		return VM_FAULT_SIGBUS;
 
 	if (is_inode_flag_set(inode, FI_COMPRESS_RELEASED)) {
-- 
2.53.0.1213.gd9a14994de-goog



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Re: [f2fs-dev] [PATCH] f2fs: do not support mmap write for large folio

[Daeho Jeong]

On Mon, Apr 6, 2026 at 8:56 AM Jaegeuk Kim via Linux-f2fs-devel
<linux-f2fs-devel@lists.sourceforge.net> wrote:
>
> Let's check mmmap writes onto the large folio.

typo? mmap?

>
> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> ---
>  fs/f2fs/file.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> index 2c4880f24b54..edfc3a374c40 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -82,7 +82,7 @@ static vm_fault_t f2fs_vm_page_mkwrite(struct vm_fault *vmf)
>         int err = 0;
>         vm_fault_t ret;
>
> -       if (unlikely(IS_IMMUTABLE(inode)))

Did you remove this intentionally?

> +       if (mapping_large_folio_support(inode->i_mapping))
>                 return VM_FAULT_SIGBUS;
>
>         if (is_inode_flag_set(inode, FI_COMPRESS_RELEASED)) {
> --
> 2.53.0.1213.gd9a14994de-goog
>
>
>
> _______________________________________________
> Linux-f2fs-devel mailing list
> Linux-f2fs-devel@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel


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Re: [f2fs-dev] [PATCH] f2fs: do not support mmap write for large folio

[Jaegeuk Kim via Linux-f2fs-devel]

On 04/06, Daeho Jeong wrote:
> On Mon, Apr 6, 2026 at 8:56 AM Jaegeuk Kim via Linux-f2fs-devel
> <linux-f2fs-devel@lists.sourceforge.net> wrote:
> >
> > Let's check mmmap writes onto the large folio.
> 
> typo? mmap?
> 
> >
> > Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> > ---
> >  fs/f2fs/file.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> > index 2c4880f24b54..edfc3a374c40 100644
> > --- a/fs/f2fs/file.c
> > +++ b/fs/f2fs/file.c
> > @@ -82,7 +82,7 @@ static vm_fault_t f2fs_vm_page_mkwrite(struct vm_fault *vmf)
> >         int err = 0;
> >         vm_fault_t ret;
> >
> > -       if (unlikely(IS_IMMUTABLE(inode)))
> 
> Did you remove this intentionally?

Ah, let me remain it back to isolate the change.

> 
> > +       if (mapping_large_folio_support(inode->i_mapping))
> >                 return VM_FAULT_SIGBUS;
> >
> >         if (is_inode_flag_set(inode, FI_COMPRESS_RELEASED)) {
> > --
> > 2.53.0.1213.gd9a14994de-goog
> >
> >
> >
> > _______________________________________________
> > Linux-f2fs-devel mailing list
> > Linux-f2fs-devel@lists.sourceforge.net
> > https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel


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Re: [f2fs-dev] [PATCH v3] f2fs: do not support mmap write for large folio

[Jaegeuk Kim via Linux-f2fs-devel]

Let's check mmap writes onto the large folio, since we don't support writing
large folios.

Reviewed-by: Daeho Jeong <daehojeong@google.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
---

 - log v2:
  : add comments 

 fs/f2fs/file.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 2c4880f24b54..c0220cd7b332 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -82,7 +82,12 @@ static vm_fault_t f2fs_vm_page_mkwrite(struct vm_fault *vmf)
 	int err = 0;
 	vm_fault_t ret;
 
-	if (unlikely(IS_IMMUTABLE(inode)))
+	/*
+	 * We only support large folio on the read case.
+	 * Don't make any dirty pages.
+	 */
+	if (unlikely(IS_IMMUTABLE(inode)) ||
+	    mapping_large_folio_support(inode->i_mapping))
 		return VM_FAULT_SIGBUS;
 
 	if (is_inode_flag_set(inode, FI_COMPRESS_RELEASED)) {
-- 
2.53.0.1213.gd9a14994de-goog



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Re: [f2fs-dev] [PATCH v3] f2fs: do not support mmap write for large folio

[Christoph Hellwig]

[adding back fsdevel and mm to the discussion]

On Wed, Apr 08, 2026 at 06:13:06PM +0000, Jaegeuk Kim wrote:
> Let's check mmap writes onto the large folio, since we don't support writing
> large folios.

What does this fix?  As state in the previous round of discussion f2fs
only support large folios for immutable files, how do you get ->mkwrite
called for them.

The only way I can think of that is when clearing the immutable flag,
but simply rejecting writes with SIGBUS after that seems like it's
breaking the expected API, and I don't see handling for normal writes
after that either.


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Re: [f2fs-dev] [PATCH v3] f2fs: do not support mmap write for large folio

[Jaegeuk Kim via Linux-f2fs-devel]

On 04/08, Christoph Hellwig wrote:
> [adding back fsdevel and mm to the discussion]
> 
> On Wed, Apr 08, 2026 at 06:13:06PM +0000, Jaegeuk Kim wrote:
> > Let's check mmap writes onto the large folio, since we don't support writing
> > large folios.
> 
> What does this fix?  As state in the previous round of discussion f2fs
> only support large folios for immutable files, how do you get ->mkwrite
> called for them.

I'm approaching this as a safeguard first, since in any buggy case, this will
crash the filesystem.

> 
> The only way I can think of that is when clearing the immutable flag,
> but simply rejecting writes with SIGBUS after that seems like it's
> breaking the expected API, and I don't see handling for normal writes
> after that either.


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Re: [f2fs-dev] [PATCH v3] f2fs: do not support mmap write for large folio

[Chao Yu via Linux-f2fs-devel]

On 4/9/2026 2:13 AM, Jaegeuk Kim via Linux-f2fs-devel wrote:
> Let's check mmap writes onto the large folio, since we don't support writing
> large folios.
> 
> Reviewed-by: Daeho Jeong <daehojeong@google.com>
> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> ---
> 
>   - log v2:
>    : add comments
> 
>   fs/f2fs/file.c | 7 ++++++-
>   1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> index 2c4880f24b54..c0220cd7b332 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -82,7 +82,12 @@ static vm_fault_t f2fs_vm_page_mkwrite(struct vm_fault *vmf)
>   	int err = 0;
>   	vm_fault_t ret;
>   
> -	if (unlikely(IS_IMMUTABLE(inode)))
> +	/*
> +	 * We only support large folio on the read case.
> +	 * Don't make any dirty pages.
> +	 */
> +	if (unlikely(IS_IMMUTABLE(inode)) ||
> +	    mapping_large_folio_support(inode->i_mapping))
>   		return VM_FAULT_SIGBUS;

The code itself looks good, since it's an impossible case, should we
use f2fs_bug_on(, mapping_large_folio_support()) to catch any bug case
rather than just returning error here w/o log?

Thanks,

>   
>   	if (is_inode_flag_set(inode, FI_COMPRESS_RELEASED)) {



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Re: [f2fs-dev] [PATCH v4] f2fs: do not support mmap write for large folio

[Jaegeuk Kim via Linux-f2fs-devel]

Let's check mmap writes onto the large folio, since we don't support writing
large folios.

Reviewed-by: Daeho Jeong <daehojeong@google.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
---

 - add f2fs_err to catch any issue

 fs/f2fs/file.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 2c4880f24b54..e917342cb828 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -82,8 +82,17 @@ static vm_fault_t f2fs_vm_page_mkwrite(struct vm_fault *vmf)
 	int err = 0;
 	vm_fault_t ret;
 
-	if (unlikely(IS_IMMUTABLE(inode)))
+	/*
+	 * We only support large folio on the read case.
+	 * Don't make any dirty pages.
+	 */
+	if (unlikely(IS_IMMUTABLE(inode)) ||
+	    mapping_large_folio_support(inode->i_mapping)) {
+		f2fs_err(sbi, "Not expected: immutable: %d large_folio: %d",
+				IS_IMMUTABLE(inode),
+				mapping_large_folio_support(inode->i_mapping));
 		return VM_FAULT_SIGBUS;
+	}
 
 	if (is_inode_flag_set(inode, FI_COMPRESS_RELEASED)) {
 		err = -EIO;
-- 
2.54.0.rc0.605.g598a273b03-goog



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Re: [f2fs-dev] [PATCH v3] f2fs: do not support mmap write for large folio

[Jaegeuk Kim via Linux-f2fs-devel]

On 04/13, Chao Yu wrote:
> On 4/9/2026 2:13 AM, Jaegeuk Kim via Linux-f2fs-devel wrote:
> > Let's check mmap writes onto the large folio, since we don't support writing
> > large folios.
> > 
> > Reviewed-by: Daeho Jeong <daehojeong@google.com>
> > Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> > ---
> > 
> >   - log v2:
> >    : add comments
> > 
> >   fs/f2fs/file.c | 7 ++++++-
> >   1 file changed, 6 insertions(+), 1 deletion(-)
> > 
> > diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> > index 2c4880f24b54..c0220cd7b332 100644
> > --- a/fs/f2fs/file.c
> > +++ b/fs/f2fs/file.c
> > @@ -82,7 +82,12 @@ static vm_fault_t f2fs_vm_page_mkwrite(struct vm_fault *vmf)
> >   	int err = 0;
> >   	vm_fault_t ret;
> > -	if (unlikely(IS_IMMUTABLE(inode)))
> > +	/*
> > +	 * We only support large folio on the read case.
> > +	 * Don't make any dirty pages.
> > +	 */
> > +	if (unlikely(IS_IMMUTABLE(inode)) ||
> > +	    mapping_large_folio_support(inode->i_mapping))
> >   		return VM_FAULT_SIGBUS;
> 
> The code itself looks good, since it's an impossible case, should we
> use f2fs_bug_on(, mapping_large_folio_support()) to catch any bug case
> rather than just returning error here w/o log?

Instead of kernel panicing for the production, I'd leave a kernel message first.

> 
> Thanks,
> 
> >   	if (is_inode_flag_set(inode, FI_COMPRESS_RELEASED)) {


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Re: [f2fs-dev] [PATCH v4] f2fs: do not support mmap write for large folio

[Chao Yu via Linux-f2fs-devel]

On 4/14/2026 6:46 AM, Jaegeuk Kim via Linux-f2fs-devel wrote:
> Let's check mmap writes onto the large folio, since we don't support writing
> large folios.
> 
> Reviewed-by: Daeho Jeong <daehojeong@google.com>
> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

Reviewed-by: Chao Yu <chao@kernel.org>

Thanks,


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