| Message ID | 20180620221503.25237-3-ross.zwisler@linux.intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed 20-06-18 16:15:03, Ross Zwisler wrote: > 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@linux.intel.com> > --- > 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; > + } This could be shortened as: if (WARN_ON_ONCE(!rwsem_is_locked(&ei->i_mmap_sem))) { } couldn't it? Besides that the patch looks to me. You can add: Reviewed-by: Jan Kara <jack@suse.cz> And I'm really wondering which protection are we still missing that you are still able to hit the warning with these patches applied. Honza
On Wed 20-06-18 16:15:03, Ross Zwisler wrote: > 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); One comment here: I don't think ext4_break_layouts() is necessary here. ext4_truncate_failed_write() exists to truncate blocks beyond EOF. As such these blocks could never be even mmaped, let alone pinned by GUP. Maybe just add a comment that blocks we are truncating here were never visible to userspace and so we don't need ext4_break_layouts() protection. Honza
On Fri, Jun 22, 2018 at 10:19:15AM +0200, Jan Kara wrote: > On Wed 20-06-18 16:15:03, Ross Zwisler wrote: > > 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@linux.intel.com> > > --- > > 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; > > + } > > This could be shortened as: > > if (WARN_ON_ONCE(!rwsem_is_locked(&ei->i_mmap_sem))) { > } > > couldn't it? Yep, that's much better. Thank you for the review. > Besides that the patch looks to me. You can add: > > Reviewed-by: Jan Kara <jack@suse.cz> > > And I'm really wondering which protection are we still missing that you are > still able to hit the warning with these patches applied. I'm also very curious and am going to dig into that this week.
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);
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@linux.intel.com> --- 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(+)