| Message ID | 20201108140307.1385745-7-cgxu519@mykernel.net (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | implement containerized syncfs for overlayfs | expand |
---- 在 星期日, 2020-11-08 22:03:03 Chengguang Xu <cgxu519@mykernel.net> 撰写 ---- > Overlayfs cannot be notified when mmapped area gets dirty, > so we need to proactively mark inode dirty in ->mmap operation. > > Signed-off-by: Chengguang Xu <cgxu519@mykernel.net> > --- > fs/overlayfs/file.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c > index efccb7c1f9bc..662252047fff 100644 > --- a/fs/overlayfs/file.c > +++ b/fs/overlayfs/file.c > @@ -486,6 +486,8 @@ static int ovl_mmap(struct file *file, struct vm_area_struct *vma) > /* Drop reference count from new vm_file value */ > fput(realfile); > } else { > + if (vma->vm_flags & (VM_SHARED|VM_MAYSHARE)) Maybe it's better to mark dirty only having upper inode. > + ovl_mark_inode_dirty(file_inode(file)); > /* Drop reference count from previous vm_file value */ > fput(file); > } > -- > 2.26.2 > > >
On Wed, Nov 11, 2020 at 3:05 PM Chengguang Xu <cgxu519@mykernel.net> wrote: > > ---- 在 星期日, 2020-11-08 22:03:03 Chengguang Xu <cgxu519@mykernel.net> 撰写 ---- > > Overlayfs cannot be notified when mmapped area gets dirty, > > so we need to proactively mark inode dirty in ->mmap operation. > > > > Signed-off-by: Chengguang Xu <cgxu519@mykernel.net> > > --- > > fs/overlayfs/file.c | 2 ++ > > 1 file changed, 2 insertions(+) > > > > diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c > > index efccb7c1f9bc..662252047fff 100644 > > --- a/fs/overlayfs/file.c > > +++ b/fs/overlayfs/file.c > > @@ -486,6 +486,8 @@ static int ovl_mmap(struct file *file, struct vm_area_struct *vma) > > /* Drop reference count from new vm_file value */ > > fput(realfile); > > } else { > > + if (vma->vm_flags & (VM_SHARED|VM_MAYSHARE)) > > Maybe it's better to mark dirty only having upper inode. > Yeh. And since mapping_map_writable() is only called if VM_SHARED flag is set (and not VM_MAYSHARE), we are not going to re-dirty an inode on account of VM_MAYSHARE alone, so I wonder why we need to mark it dirty here on account of VM_MAYSHARE? Thanks, Amir.
---- 在 星期三, 2020-11-11 23:20:56 Amir Goldstein <amir73il@gmail.com> 撰写 ---- > On Wed, Nov 11, 2020 at 3:05 PM Chengguang Xu <cgxu519@mykernel.net> wrote: > > > > ---- 在 星期日, 2020-11-08 22:03:03 Chengguang Xu <cgxu519@mykernel.net> 撰写 ---- > > > Overlayfs cannot be notified when mmapped area gets dirty, > > > so we need to proactively mark inode dirty in ->mmap operation. > > > > > > Signed-off-by: Chengguang Xu <cgxu519@mykernel.net> > > > --- > > > fs/overlayfs/file.c | 2 ++ > > > 1 file changed, 2 insertions(+) > > > > > > diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c > > > index efccb7c1f9bc..662252047fff 100644 > > > --- a/fs/overlayfs/file.c > > > +++ b/fs/overlayfs/file.c > > > @@ -486,6 +486,8 @@ static int ovl_mmap(struct file *file, struct vm_area_struct *vma) > > > /* Drop reference count from new vm_file value */ > > > fput(realfile); > > > } else { > > > + if (vma->vm_flags & (VM_SHARED|VM_MAYSHARE)) > > > > Maybe it's better to mark dirty only having upper inode. > > > > Yeh. > > And since mapping_map_writable() is only called if VM_SHARED flag > is set (and not VM_MAYSHARE), we are not going to re-dirty an inode on > account of VM_MAYSHARE alone, so I wonder why we need to mark it > dirty here on account of VM_MAYSHARE? > Yeah, you are right. It just means the pages in this memory region can be mapped by other process with shared+write mode and this is actually meaningless in our case. So let's just ignore it. :-) Thanks, Chengguang
diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c index efccb7c1f9bc..662252047fff 100644 --- a/fs/overlayfs/file.c +++ b/fs/overlayfs/file.c @@ -486,6 +486,8 @@ static int ovl_mmap(struct file *file, struct vm_area_struct *vma) /* Drop reference count from new vm_file value */ fput(realfile); } else { + if (vma->vm_flags & (VM_SHARED|VM_MAYSHARE)) + ovl_mark_inode_dirty(file_inode(file)); /* Drop reference count from previous vm_file value */ fput(file); }
Overlayfs cannot be notified when mmapped area gets dirty, so we need to proactively mark inode dirty in ->mmap operation. Signed-off-by: Chengguang Xu <cgxu519@mykernel.net> --- fs/overlayfs/file.c | 2 ++ 1 file changed, 2 insertions(+)