From: "Darrick J. Wong" <darrick.wong@oracle.com>
To: Goldwyn Rodrigues <rgoldwyn@suse.de>
Cc: linux-btrfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
Goldwyn Rodrigues <rgoldwyn@suse.com>
Subject: Re: [PATCH 15/15] btrfs: Writeprotect mmap pages on snapshot
Date: Thu, 28 Mar 2019 08:48:16 -0700 [thread overview]
Message-ID: <20190328154816.GG1172@magnolia> (raw)
In-Reply-To: <20190326190301.32365-16-rgoldwyn@suse.de>
On Tue, Mar 26, 2019 at 02:03:01PM -0500, 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.
>
> This looks hackish. Other alternatives could be to create another
> list for mmap'd files or rename delalloc_inodes to writeback_inodes.
> Suggestions?
Is there a function to invalidate only the writable mappings in the
pagecache? Could there be?
> Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
> ---
> fs/btrfs/ctree.h | 3 ++-
> fs/btrfs/dax.c | 7 +++++++
> fs/btrfs/inode.c | 13 ++++++++++++-
> fs/dax.c | 3 +++
> 4 files changed, 24 insertions(+), 2 deletions(-)
>
> diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
> index 21068dc4a95a..68a63d93556a 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 d73945d50b88..bcb961242c74 100644
> --- a/fs/btrfs/dax.c
> +++ b/fs/btrfs/dax.c
> @@ -166,10 +166,17 @@ 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 5350e5f23728..3b72c1c96b34 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))
> diff --git a/fs/dax.c b/fs/dax.c
> index 93146142bb00..c42e9cb486ef 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -753,6 +753,9 @@ static void *dax_insert_entry(struct xa_state *xas,
> if (dirty)
> xas_set_mark(xas, PAGECACHE_TAG_DIRTY);
>
> + if (cow)
> + xas_set_mark(xas, PAGECACHE_TAG_TOWRITE);
> +
Was this supposed to go with the dax_insert_entry changes (patch 9)?
--D
> xas_unlock_irq(xas);
> return entry;
> }
> --
> 2.16.4
>
next prev parent reply other threads:[~2019-03-28 15:48 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20190326190301.32365-1-rgoldwyn@suse.de>
2019-03-26 19:02 ` [PATCH 01/15] btrfs: create a mount option for dax Goldwyn Rodrigues
2019-03-26 19:10 ` Matthew Wilcox
2019-03-27 11:00 ` Goldwyn Rodrigues
2019-03-27 12:00 ` Matthew Wilcox
2019-03-27 12:26 ` Goldwyn Rodrigues
2019-03-27 23:31 ` Goldwyn Rodrigues
2019-03-27 17:38 ` Adam Borowski
2019-03-28 14:49 ` David Sterba
2019-03-28 17:28 ` David Sterba
2019-03-28 17:57 ` Darrick J. Wong
2019-04-01 20:43 ` Goldwyn Rodrigues
2019-03-26 19:02 ` [PATCH 02/15] btrfs: Carve out btrfs_get_extent_map_write() out of btrfs_get_blocks_write() Goldwyn Rodrigues
2019-03-26 19:02 ` [PATCH 03/15] btrfs: basic dax read Goldwyn Rodrigues
2019-03-26 19:02 ` [PATCH 04/15] dax: Introduce IOMAP_F_COW for copy-on-write Goldwyn Rodrigues
2019-03-27 17:54 ` Darrick J. Wong
2019-03-27 18:58 ` Goldwyn Rodrigues
2019-03-28 14:45 ` Darrick J. Wong
2019-04-01 4:38 ` Dave Chinner
2019-04-01 21:41 ` Goldwyn Rodrigues
2019-04-01 23:06 ` Dave Chinner
2019-04-03 1:56 ` Goldwyn Rodrigues
2019-04-03 3:20 ` Dave Chinner
2019-04-07 7:26 ` Christoph Hellwig
2019-03-26 19:02 ` [PATCH 05/15] btrfs: return whether extent is nocow or not Goldwyn Rodrigues
2019-03-31 18:42 ` Nikolay Borisov
2019-03-26 19:02 ` [PATCH 06/15] btrfs: Rename __endio_write_update_ordered() to btrfs_update_ordered_extent() Goldwyn Rodrigues
2019-03-26 19:02 ` [PATCH 07/15] btrfs: add dax write support Goldwyn Rodrigues
2019-03-28 14:53 ` Darrick J. Wong
2019-04-01 20:39 ` Goldwyn Rodrigues
2019-03-26 19:02 ` [PATCH 08/15] dax: add dax_iomap_cow to copy a mmap page before writing Goldwyn Rodrigues
2019-03-28 15:41 ` Darrick J. Wong
2019-03-26 19:02 ` [PATCH 09/15] btrfs: add dax mmap support Goldwyn Rodrigues
2019-03-28 15:45 ` Darrick J. Wong
2019-03-26 19:02 ` [PATCH 10/15] btrfs: Add dax specific address_space_operations Goldwyn Rodrigues
2019-03-26 19:02 ` [PATCH 11/15] fs: dedup file range to use a compare function Goldwyn Rodrigues
2019-03-28 17:04 ` Darrick J. Wong
2019-04-01 20:36 ` Goldwyn Rodrigues
2019-03-26 19:02 ` [PATCH 12/15] btrfs: trace functions for btrfs_iomap_begin/end Goldwyn Rodrigues
2019-03-26 19:02 ` [PATCH 13/15] btrfs: handle dax page zeroing Goldwyn Rodrigues
2019-03-26 19:03 ` [PATCH 14/15] btrfs: Disable dax-based defrag and send Goldwyn Rodrigues
2019-03-26 19:03 ` [PATCH 15/15] btrfs: Writeprotect mmap pages on snapshot Goldwyn Rodrigues
2019-03-28 15:48 ` Darrick J. Wong [this message]
2019-03-26 19:09 ` [PATCH v2 00/15] btrfs dax support Goldwyn Rodrigues
2019-03-27 20:14 ` Adam Borowski
2019-03-27 23:26 ` Goldwyn Rodrigues
2019-03-28 10:24 ` [PATCH] btrfs: allow MAP_SYNC mmap Adam Borowski
2019-03-28 10:42 ` Adam Borowski
2019-04-01 20:08 ` Goldwyn Rodrigues
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