| Message ID | 20190429172649.8288-17-rgoldwyn@suse.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | btrfs dax support | expand |
On Mon 29-04-19 12:26:47, Goldwyn Rodrigues wrote: > From: Goldwyn Rodrigues <rgoldwyn@suse.com> > > Inorder to make sure mmap'd files don't change after snapshot, > writeprotect the mmap pages on snapshot. This is done by performing > a data writeback on the pages (which simply mark the pages are > wrprotected). This way if the user process tries to access the memory > we will get another fault and we can perform a CoW. > > In order to accomplish this, we tag all CoW pages as > PAGECACHE_TAG_TOWRITE, and add the mmapd inode in delalloc_inodes. > During snapshot, it starts writeback of all delalloc'd inodes and > here we perform a data writeback. We don't want to keep the inodes > in delalloc_inodes until it umount (WARN_ON), so we remove it > during inode evictions. > > Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com> OK, so here you use PAGECACHE_TAG_TOWRITE. But why is not PAGECACHE_TAG_DIRTY enough for you? Also why isn't the same needed also for normal non-DAX inodes? There you also need to trigger CoW on mmap write so I just don't see the difference... Honza > --- > fs/btrfs/ctree.h | 3 ++- > fs/btrfs/dax.c | 7 +++++++ > fs/btrfs/inode.c | 13 ++++++++++++- > 3 files changed, 21 insertions(+), 2 deletions(-) > > diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h > index ee1ed18f8b3c..d1b70f24adeb 100644 > --- a/fs/btrfs/ctree.h > +++ b/fs/btrfs/ctree.h > @@ -3252,7 +3252,8 @@ int btrfs_create_subvol_root(struct btrfs_trans_handle *trans, > struct btrfs_root *new_root, > struct btrfs_root *parent_root, > u64 new_dirid); > - void btrfs_set_delalloc_extent(struct inode *inode, struct extent_state *state, > +void btrfs_add_delalloc_inodes(struct btrfs_root *root, struct inode *inode); > +void btrfs_set_delalloc_extent(struct inode *inode, struct extent_state *state, > unsigned *bits); > void btrfs_clear_delalloc_extent(struct inode *inode, > struct extent_state *state, unsigned *bits); > diff --git a/fs/btrfs/dax.c b/fs/btrfs/dax.c > index bf2ddac5b5a1..20ec2ec49c68 100644 > --- a/fs/btrfs/dax.c > +++ b/fs/btrfs/dax.c > @@ -222,10 +222,17 @@ vm_fault_t btrfs_dax_fault(struct vm_fault *vmf) > { > vm_fault_t ret; > pfn_t pfn; > + struct inode *inode = file_inode(vmf->vma->vm_file); > + struct btrfs_inode *binode = BTRFS_I(inode); > ret = dax_iomap_fault(vmf, PE_SIZE_PTE, &pfn, NULL, &btrfs_iomap_ops); > if (ret & VM_FAULT_NEEDDSYNC) > ret = dax_finish_sync_fault(vmf, PE_SIZE_PTE, pfn); > > + /* Insert into delalloc so we get writeback calls on snapshots */ > + if (vmf->flags & FAULT_FLAG_WRITE && > + !test_bit(BTRFS_INODE_IN_DELALLOC_LIST, &binode->runtime_flags)) > + btrfs_add_delalloc_inodes(binode->root, inode); > + > return ret; > } > > diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c > index 7e88280a2c3b..e98fb512e1ca 100644 > --- a/fs/btrfs/inode.c > +++ b/fs/btrfs/inode.c > @@ -1713,7 +1713,7 @@ void btrfs_merge_delalloc_extent(struct inode *inode, struct extent_state *new, > spin_unlock(&BTRFS_I(inode)->lock); > } > > -static void btrfs_add_delalloc_inodes(struct btrfs_root *root, > +void btrfs_add_delalloc_inodes(struct btrfs_root *root, > struct inode *inode) > { > struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb); > @@ -5358,12 +5358,17 @@ void btrfs_evict_inode(struct inode *inode) > { > struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb); > struct btrfs_trans_handle *trans; > + struct btrfs_inode *binode = BTRFS_I(inode); > struct btrfs_root *root = BTRFS_I(inode)->root; > struct btrfs_block_rsv *rsv; > int ret; > > trace_btrfs_inode_evict(inode); > > + if (IS_DAX(inode) > + && test_bit(BTRFS_INODE_IN_DELALLOC_LIST, &binode->runtime_flags)) > + btrfs_del_delalloc_inode(root, binode); > + > if (!root) { > clear_inode(inode); > return; > @@ -8683,6 +8688,10 @@ static int btrfs_dax_writepages(struct address_space *mapping, > { > struct inode *inode = mapping->host; > struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb); > + struct btrfs_inode *binode = BTRFS_I(inode); > + if ((wbc->sync_mode == WB_SYNC_ALL) && > + test_bit(BTRFS_INODE_IN_DELALLOC_LIST, &binode->runtime_flags)) > + btrfs_del_delalloc_inode(binode->root, binode); > return dax_writeback_mapping_range(mapping, fs_info->fs_devices->latest_bdev, > wbc); > } > @@ -9981,6 +9990,8 @@ static void btrfs_run_delalloc_work(struct btrfs_work *work) > delalloc_work = container_of(work, struct btrfs_delalloc_work, > work); > inode = delalloc_work->inode; > + if (IS_DAX(inode)) > + filemap_fdatawrite(inode->i_mapping); > filemap_flush(inode->i_mapping); > if (test_bit(BTRFS_INODE_HAS_ASYNC_EXTENT, > &BTRFS_I(inode)->runtime_flags)) > -- > 2.16.4 >
On 16:04 23/05, Jan Kara wrote: > On Mon 29-04-19 12:26:47, Goldwyn Rodrigues wrote: > > From: Goldwyn Rodrigues <rgoldwyn@suse.com> > > > > Inorder to make sure mmap'd files don't change after snapshot, > > writeprotect the mmap pages on snapshot. This is done by performing > > a data writeback on the pages (which simply mark the pages are > > wrprotected). This way if the user process tries to access the memory > > we will get another fault and we can perform a CoW. > > > > In order to accomplish this, we tag all CoW pages as > > PAGECACHE_TAG_TOWRITE, and add the mmapd inode in delalloc_inodes. > > During snapshot, it starts writeback of all delalloc'd inodes and > > here we perform a data writeback. We don't want to keep the inodes > > in delalloc_inodes until it umount (WARN_ON), so we remove it > > during inode evictions. > > > > Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com> > > OK, so here you use PAGECACHE_TAG_TOWRITE. But why is not > PAGECACHE_TAG_DIRTY enough for you? Also why isn't the same needed also for > normal non-DAX inodes? There you also need to trigger CoW on mmap write so > I just don't see the difference... Because dax_writeback_mapping_range() writebacks pages marked PAGECACHE_TAG_TOWRITE and not PAGECACHE_TAG_DIRTY. Should it writeback pages marked as PAGECACHE_TAG_DIRTY as well?
On Thu 23-05-19 10:27:22, Goldwyn Rodrigues wrote: > On 16:04 23/05, Jan Kara wrote: > > On Mon 29-04-19 12:26:47, Goldwyn Rodrigues wrote: > > > From: Goldwyn Rodrigues <rgoldwyn@suse.com> > > > > > > Inorder to make sure mmap'd files don't change after snapshot, > > > writeprotect the mmap pages on snapshot. This is done by performing > > > a data writeback on the pages (which simply mark the pages are > > > wrprotected). This way if the user process tries to access the memory > > > we will get another fault and we can perform a CoW. > > > > > > In order to accomplish this, we tag all CoW pages as > > > PAGECACHE_TAG_TOWRITE, and add the mmapd inode in delalloc_inodes. > > > During snapshot, it starts writeback of all delalloc'd inodes and > > > here we perform a data writeback. We don't want to keep the inodes > > > in delalloc_inodes until it umount (WARN_ON), so we remove it > > > during inode evictions. > > > > > > Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com> > > > > OK, so here you use PAGECACHE_TAG_TOWRITE. But why is not > > PAGECACHE_TAG_DIRTY enough for you? Also why isn't the same needed also for > > normal non-DAX inodes? There you also need to trigger CoW on mmap write so > > I just don't see the difference... > > Because dax_writeback_mapping_range() writebacks pages marked > PAGECACHE_TAG_TOWRITE and not PAGECACHE_TAG_DIRTY. Should it > writeback pages marked as PAGECACHE_TAG_DIRTY as well? It does writeback PAGECACHE_TAG_DIRTY pages - tag_pages_for_writeback() moves PAGECACHE_TAG_DIRTY to PAGECACHE_TAG_TOWRITE... Honza
On 21:07 23/05, Jan Kara wrote: > On Thu 23-05-19 10:27:22, Goldwyn Rodrigues wrote: > > On 16:04 23/05, Jan Kara wrote: > > > On Mon 29-04-19 12:26:47, Goldwyn Rodrigues wrote: > > > > From: Goldwyn Rodrigues <rgoldwyn@suse.com> > > > > > > > > Inorder to make sure mmap'd files don't change after snapshot, > > > > writeprotect the mmap pages on snapshot. This is done by performing > > > > a data writeback on the pages (which simply mark the pages are > > > > wrprotected). This way if the user process tries to access the memory > > > > we will get another fault and we can perform a CoW. > > > > > > > > In order to accomplish this, we tag all CoW pages as > > > > PAGECACHE_TAG_TOWRITE, and add the mmapd inode in delalloc_inodes. > > > > During snapshot, it starts writeback of all delalloc'd inodes and > > > > here we perform a data writeback. We don't want to keep the inodes > > > > in delalloc_inodes until it umount (WARN_ON), so we remove it > > > > during inode evictions. > > > > > > > > Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com> > > > > > > OK, so here you use PAGECACHE_TAG_TOWRITE. But why is not > > > PAGECACHE_TAG_DIRTY enough for you? Also why isn't the same needed also for > > > normal non-DAX inodes? There you also need to trigger CoW on mmap write so > > > I just don't see the difference... > > > > Because dax_writeback_mapping_range() writebacks pages marked > > PAGECACHE_TAG_TOWRITE and not PAGECACHE_TAG_DIRTY. Should it > > writeback pages marked as PAGECACHE_TAG_DIRTY as well? > > It does writeback PAGECACHE_TAG_DIRTY pages - tag_pages_for_writeback() > moves PAGECACHE_TAG_DIRTY to PAGECACHE_TAG_TOWRITE... Yes, I missed that. It just needs a writeback with WB_SYNC_ALL. Thanks!
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h index ee1ed18f8b3c..d1b70f24adeb 100644 --- a/fs/btrfs/ctree.h +++ b/fs/btrfs/ctree.h @@ -3252,7 +3252,8 @@ int btrfs_create_subvol_root(struct btrfs_trans_handle *trans, struct btrfs_root *new_root, struct btrfs_root *parent_root, u64 new_dirid); - void btrfs_set_delalloc_extent(struct inode *inode, struct extent_state *state, +void btrfs_add_delalloc_inodes(struct btrfs_root *root, struct inode *inode); +void btrfs_set_delalloc_extent(struct inode *inode, struct extent_state *state, unsigned *bits); void btrfs_clear_delalloc_extent(struct inode *inode, struct extent_state *state, unsigned *bits); diff --git a/fs/btrfs/dax.c b/fs/btrfs/dax.c index bf2ddac5b5a1..20ec2ec49c68 100644 --- a/fs/btrfs/dax.c +++ b/fs/btrfs/dax.c @@ -222,10 +222,17 @@ vm_fault_t btrfs_dax_fault(struct vm_fault *vmf) { vm_fault_t ret; pfn_t pfn; + struct inode *inode = file_inode(vmf->vma->vm_file); + struct btrfs_inode *binode = BTRFS_I(inode); ret = dax_iomap_fault(vmf, PE_SIZE_PTE, &pfn, NULL, &btrfs_iomap_ops); if (ret & VM_FAULT_NEEDDSYNC) ret = dax_finish_sync_fault(vmf, PE_SIZE_PTE, pfn); + /* Insert into delalloc so we get writeback calls on snapshots */ + if (vmf->flags & FAULT_FLAG_WRITE && + !test_bit(BTRFS_INODE_IN_DELALLOC_LIST, &binode->runtime_flags)) + btrfs_add_delalloc_inodes(binode->root, inode); + return ret; } diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index 7e88280a2c3b..e98fb512e1ca 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -1713,7 +1713,7 @@ void btrfs_merge_delalloc_extent(struct inode *inode, struct extent_state *new, spin_unlock(&BTRFS_I(inode)->lock); } -static void btrfs_add_delalloc_inodes(struct btrfs_root *root, +void btrfs_add_delalloc_inodes(struct btrfs_root *root, struct inode *inode) { struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb); @@ -5358,12 +5358,17 @@ void btrfs_evict_inode(struct inode *inode) { struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb); struct btrfs_trans_handle *trans; + struct btrfs_inode *binode = BTRFS_I(inode); struct btrfs_root *root = BTRFS_I(inode)->root; struct btrfs_block_rsv *rsv; int ret; trace_btrfs_inode_evict(inode); + if (IS_DAX(inode) + && test_bit(BTRFS_INODE_IN_DELALLOC_LIST, &binode->runtime_flags)) + btrfs_del_delalloc_inode(root, binode); + if (!root) { clear_inode(inode); return; @@ -8683,6 +8688,10 @@ static int btrfs_dax_writepages(struct address_space *mapping, { struct inode *inode = mapping->host; struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb); + struct btrfs_inode *binode = BTRFS_I(inode); + if ((wbc->sync_mode == WB_SYNC_ALL) && + test_bit(BTRFS_INODE_IN_DELALLOC_LIST, &binode->runtime_flags)) + btrfs_del_delalloc_inode(binode->root, binode); return dax_writeback_mapping_range(mapping, fs_info->fs_devices->latest_bdev, wbc); } @@ -9981,6 +9990,8 @@ static void btrfs_run_delalloc_work(struct btrfs_work *work) delalloc_work = container_of(work, struct btrfs_delalloc_work, work); inode = delalloc_work->inode; + if (IS_DAX(inode)) + filemap_fdatawrite(inode->i_mapping); filemap_flush(inode->i_mapping); if (test_bit(BTRFS_INODE_HAS_ASYNC_EXTENT, &BTRFS_I(inode)->runtime_flags))