Inodes using DAX should only ever have exceptional entries in their page caches. Make this clear by warning if the iteration in dax_layout_busy_page() ever sees a non-exceptional entry, and by adding a comment for the pagevec_release() call which only deals with struct page pointers. Signed-off-by: Ross Zwisler <ross.zwisler(a)linux.intel.com&gt; --- fs/dax.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/fs/dax.c b/fs/dax.c index 641192808bb6..4a5e31f8a2d4 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -566,7 +566,7 @@ struct page *dax_layout_busy_page(struct address_space *mapping) if (index >= end) break; - if (!radix_tree_exceptional_entry(pvec_ent)) + if (WARN_ON_ONCE(!radix_tree_exceptional_entry(pvec_ent))) continue; xa_lock_irq(&mapping->i_pages); @@ -578,6 +578,13 @@ struct page *dax_layout_busy_page(struct address_space *mapping) if (page) break; } + + /* + * We don't expect normal struct page entries to exist in our + * tree, but we keep these pagevec calls so that this code is + * consistent with the common pattern for handling pagevecs + * throughout the kernel. + */ pagevec_remove_exceptionals(&pvec); pagevec_release(&pvec); index++; -- 2.14.4

Follow the lead of xfs_break_dax_layouts() and add synchronization between operations in ext4 which remove blocks from an inode (hole punch, truncate down, etc.) and pages which are pinned due to DAX DMA operations. Signed-off-by: Ross Zwisler <ross.zwisler(a)linux.intel.com&gt; --- fs/ext4/ext4.h | 1 + fs/ext4/extents.c | 12 ++++++++++++ fs/ext4/inode.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++ fs/ext4/truncate.h | 1 + 4 files changed, 62 insertions(+) diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h index 0b127853c584..34bccd64d83d 100644 --- a/fs/ext4/ext4.h +++ b/fs/ext4/ext4.h @@ -2460,6 +2460,7 @@ extern int ext4_get_inode_loc(struct inode *, struct ext4_iloc *); extern int ext4_inode_attach_jinode(struct inode *inode); extern int ext4_can_truncate(struct inode *inode); extern int ext4_truncate(struct inode *); +extern int ext4_break_layouts(struct inode *); extern int ext4_punch_hole(struct inode *inode, loff_t offset, loff_t length); extern int ext4_truncate_restart_trans(handle_t *, struct inode *, int nblocks); extern void ext4_set_inode_flags(struct inode *); diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c index 0057fe3f248d..a6aef06f455b 100644 --- a/fs/ext4/extents.c +++ b/fs/ext4/extents.c @@ -4820,6 +4820,13 @@ static long ext4_zero_range(struct file *file, loff_t offset, * released from page cache. */ down_write(&EXT4_I(inode)->i_mmap_sem); + + ret = ext4_break_layouts(inode); + if (ret) { + up_write(&EXT4_I(inode)->i_mmap_sem); + goto out_mutex; + } + ret = ext4_update_disksize_before_punch(inode, offset, len); if (ret) { up_write(&EXT4_I(inode)->i_mmap_sem); @@ -5493,6 +5500,11 @@ int ext4_collapse_range(struct inode *inode, loff_t offset, loff_t len) * page cache. */ down_write(&EXT4_I(inode)->i_mmap_sem); + + ret = ext4_break_layouts(inode); + if (ret) + goto out_mmap; + /* * Need to round down offset to be aligned with page size boundary * for page size > block size. diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 2ea07efbe016..c795e5118745 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -4193,6 +4193,41 @@ int ext4_update_disksize_before_punch(struct inode *inode, loff_t offset, return 0; } +static void ext4_wait_dax_page(struct ext4_inode_info *ei, bool *did_unlock) +{ + *did_unlock = true; + up_write(&ei->i_mmap_sem); + schedule(); + down_write(&ei->i_mmap_sem); +} + +int ext4_break_layouts(struct inode *inode) +{ + struct ext4_inode_info *ei = EXT4_I(inode); + struct page *page; + bool retry; + int error; + + if (unlikely(!rwsem_is_locked(&ei->i_mmap_sem))) { + WARN_ON_ONCE(1); + return -EINVAL; + } + + do { + retry = false; + page = dax_layout_busy_page(inode->i_mapping); + if (!page) + return 0; + + error = ___wait_var_event(&page->_refcount, + atomic_read(&page->_refcount) == 1, + TASK_INTERRUPTIBLE, 0, 0, + ext4_wait_dax_page(ei, &retry)); + } while (error == 0 && retry); + + return error; +} + /* * ext4_punch_hole: punches a hole in a file by releasing the blocks * associated with the given offset and length @@ -4266,6 +4301,11 @@ int ext4_punch_hole(struct inode *inode, loff_t offset, loff_t length) * page cache. */ down_write(&EXT4_I(inode)->i_mmap_sem); + + ret = ext4_break_layouts(inode); + if (ret) + goto out_dio; + first_block_offset = round_up(offset, sb->s_blocksize); last_block_offset = round_down((offset + length), sb->s_blocksize) - 1; @@ -5554,6 +5594,14 @@ int ext4_setattr(struct dentry *dentry, struct iattr *attr) ext4_wait_for_tail_page_commit(inode); } down_write(&EXT4_I(inode)->i_mmap_sem); + + rc = ext4_break_layouts(inode); + if (rc) { + up_write(&EXT4_I(inode)->i_mmap_sem); + error = rc; + goto err_out; + } + /* * Truncate pagecache after we've waited for commit * in data=journal mode to make pages freeable. diff --git a/fs/ext4/truncate.h b/fs/ext4/truncate.h index 0cb13badf473..a3b78241e9f6 100644 --- a/fs/ext4/truncate.h +++ b/fs/ext4/truncate.h @@ -12,6 +12,7 @@ static inline void ext4_truncate_failed_write(struct inode *inode) { down_write(&EXT4_I(inode)->i_mmap_sem); + ext4_break_layouts(inode); truncate_inode_pages(inode->i_mapping, inode->i_size); ext4_truncate(inode); up_write(&EXT4_I(inode)->i_mmap_sem); -- 2.14.4

On Fri, Jun 22, 2018 at 10:19:15AM +0200, Jan Kara wrote: Yep, that's much better. Thank you for the review. I'm also very curious and am going to dig into that this week.