| Message ID | 20190510153222.24665-1-kilobyte@angband.pl (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [for-goldwyn] btrfs: disallow MAP_SYNC outside of DAX mounts | expand |
On Fri, May 10, 2019 at 8:33 AM Adam Borowski <kilobyte@angband.pl> wrote: > > Even if allocation is done synchronously, data would be lost except on > actual pmem. Explicit msync()s don't need MAP_SYNC, and don't require > a sync per page. > > Signed-off-by: Adam Borowski <kilobyte@angband.pl> > --- > MAP_SYNC can't be allowed unconditionally, as cacheline flushes don't help > guarantee persistency in page cache. This fixes an error in my earlier > patch "btrfs: allow MAP_SYNC mmap" -- you'd probably want to amend that. > > > fs/btrfs/file.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c > index 362a9cf9dcb2..0bc5428037ba 100644 > --- a/fs/btrfs/file.c > +++ b/fs/btrfs/file.c > @@ -2233,6 +2233,13 @@ static int btrfs_file_mmap(struct file *filp, struct vm_area_struct *vma) > if (!IS_DAX(inode) && !mapping->a_ops->readpage) > return -ENOEXEC; > > + /* > + * Normal operation of btrfs is pretty much an antithesis of MAP_SYNC; > + * supporting it outside DAX is pointless. > + */ > + if (!IS_DAX(inode) && (vma->vm_flags & VM_SYNC)) > + return -EOPNOTSUPP; > + If the virtio-pmem patch set goes upstream prior to btrfs-dax support this will need to switch over to the new daxdev_mapping_supported() helper. https://lore.kernel.org/lkml/20190426050039.17460-5-pagupta@redhat.com/
> > > > Even if allocation is done synchronously, data would be lost except on > > actual pmem. Explicit msync()s don't need MAP_SYNC, and don't require > > a sync per page. > > > > Signed-off-by: Adam Borowski <kilobyte@angband.pl> > > --- > > MAP_SYNC can't be allowed unconditionally, as cacheline flushes don't help > > guarantee persistency in page cache. This fixes an error in my earlier > > patch "btrfs: allow MAP_SYNC mmap" -- you'd probably want to amend that. > > > > > > fs/btrfs/file.c | 7 +++++++ > > 1 file changed, 7 insertions(+) > > > > diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c > > index 362a9cf9dcb2..0bc5428037ba 100644 > > --- a/fs/btrfs/file.c > > +++ b/fs/btrfs/file.c > > @@ -2233,6 +2233,13 @@ static int btrfs_file_mmap(struct file *filp, > > struct vm_area_struct *vma) > > if (!IS_DAX(inode) && !mapping->a_ops->readpage) > > return -ENOEXEC; > > > > + /* > > + * Normal operation of btrfs is pretty much an antithesis of > > MAP_SYNC; > > + * supporting it outside DAX is pointless. > > + */ > > + if (!IS_DAX(inode) && (vma->vm_flags & VM_SYNC)) > > + return -EOPNOTSUPP; > > + > > If the virtio-pmem patch set goes upstream prior to btrfs-dax support > this will need to switch over to the new daxdev_mapping_supported() > helper. I was planning to do changes for virtio pmem & BTRFS. I was waiting for DAX support for BTRFS to merge upstream. Thank you, Pankaj > > https://lore.kernel.org/lkml/20190426050039.17460-5-pagupta@redhat.com/ >
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c index 362a9cf9dcb2..0bc5428037ba 100644 --- a/fs/btrfs/file.c +++ b/fs/btrfs/file.c @@ -2233,6 +2233,13 @@ static int btrfs_file_mmap(struct file *filp, struct vm_area_struct *vma) if (!IS_DAX(inode) && !mapping->a_ops->readpage) return -ENOEXEC; + /* + * Normal operation of btrfs is pretty much an antithesis of MAP_SYNC; + * supporting it outside DAX is pointless. + */ + if (!IS_DAX(inode) && (vma->vm_flags & VM_SYNC)) + return -EOPNOTSUPP; + file_accessed(filp); if (IS_DAX(inode)) vma->vm_ops = &btrfs_dax_vm_ops;
Even if allocation is done synchronously, data would be lost except on actual pmem. Explicit msync()s don't need MAP_SYNC, and don't require a sync per page. Signed-off-by: Adam Borowski <kilobyte@angband.pl> --- MAP_SYNC can't be allowed unconditionally, as cacheline flushes don't help guarantee persistency in page cache. This fixes an error in my earlier patch "btrfs: allow MAP_SYNC mmap" -- you'd probably want to amend that. fs/btrfs/file.c | 7 +++++++ 1 file changed, 7 insertions(+)