[v7,05/14] ext4, dax: introduce ext4_dax_aops

Message ID 152167305782.5268.13485258587227210521.stgit@dwillia2-desk3.amr.corp.intel.com
State Superseded
Headers show
Series
  • dax: fix dma vs truncate/hole-punch
Related show

Commit Message

Dan Williams March 21, 2018, 10:57 p.m.
In preparation for the dax implementation to start associating dax pages
to inodes via page->mapping, we need to provide a 'struct
address_space_operations' instance for dax. Otherwise, direct-I/O
triggers incorrect page cache assumptions and warnings.

Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Cc: linux-ext4@vger.kernel.org
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 fs/ext4/inode.c |   38 +++++++++++++++++++++++++++++++-------
 1 file changed, 31 insertions(+), 7 deletions(-)

Comments

Jan Kara March 29, 2018, 3:40 p.m. | #1
On Wed 21-03-18 15:57:37, Dan Williams wrote:
> In preparation for the dax implementation to start associating dax pages
> to inodes via page->mapping, we need to provide a 'struct
> address_space_operations' instance for dax. Otherwise, direct-I/O
> triggers incorrect page cache assumptions and warnings.
> 
> Cc: "Theodore Ts'o" <tytso@mit.edu>
> Cc: Andreas Dilger <adilger.kernel@dilger.ca>
> Cc: linux-ext4@vger.kernel.org
> Cc: Jan Kara <jack@suse.cz>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Looks good, just one nit below.

> @@ -3946,6 +3961,13 @@ static const struct address_space_operations ext4_da_aops = {
>  	.error_remove_page	= generic_error_remove_page,
>  };
>  
> +static const struct address_space_operations ext4_dax_aops = {
> +	.direct_IO		= ext4_direct_IO,

So ext4_direct_IO() for IS_DAX() files will just bail out. So could you
just provide ext4_dax_direct_IO() which will bail out and use it here? With
a similar comment as in xfs_vm_direct_IO() that open still needs this
method set... Thanks!

								Honza
Christoph Hellwig March 29, 2018, 6:09 p.m. | #2
On Thu, Mar 29, 2018 at 05:40:35PM +0200, Jan Kara wrote:
> So ext4_direct_IO() for IS_DAX() files will just bail out. So could you
> just provide ext4_dax_direct_IO() which will bail out and use it here? With
> a similar comment as in xfs_vm_direct_IO() that open still needs this
> method set... Thanks!

In fact a common noop_direct_IO might make sense.
Dan Williams March 29, 2018, 10:47 p.m. | #3
On Thu, Mar 29, 2018 at 11:09 AM, Christoph Hellwig <hch@lst.de> wrote:
> On Thu, Mar 29, 2018 at 05:40:35PM +0200, Jan Kara wrote:
>> So ext4_direct_IO() for IS_DAX() files will just bail out. So could you
>> just provide ext4_dax_direct_IO() which will bail out and use it here? With
>> a similar comment as in xfs_vm_direct_IO() that open still needs this
>> method set... Thanks!
>
> In fact a common noop_direct_IO might make sense.

Ok, I introduced noop_direct_IO() in "fs, dax: prepare for
dax-specific address_space_operations", and cleaned up xfs, ext4, and
ext2 accordingly. Let me know if you want to see a resend of the
series with those changes. Otherwise this will appear in -next
shortly.

Patch

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index c94780075b04..f9884e41cb39 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -2725,12 +2725,6 @@  static int ext4_writepages(struct address_space *mapping,
 	percpu_down_read(&sbi->s_journal_flag_rwsem);
 	trace_ext4_writepages(inode, wbc);
 
-	if (dax_mapping(mapping)) {
-		ret = dax_writeback_mapping_range(mapping, inode->i_sb->s_bdev,
-						  wbc);
-		goto out_writepages;
-	}
-
 	/*
 	 * No pages to write? This is mainly a kludge to avoid starting
 	 * a transaction for special inodes like journal inode on last iput()
@@ -2955,6 +2949,27 @@  static int ext4_writepages(struct address_space *mapping,
 	return ret;
 }
 
+static int ext4_dax_writepages(struct address_space *mapping,
+			       struct writeback_control *wbc)
+{
+	int ret;
+	long nr_to_write = wbc->nr_to_write;
+	struct inode *inode = mapping->host;
+	struct ext4_sb_info *sbi = EXT4_SB(mapping->host->i_sb);
+
+	if (unlikely(ext4_forced_shutdown(EXT4_SB(inode->i_sb))))
+		return -EIO;
+
+	percpu_down_read(&sbi->s_journal_flag_rwsem);
+	trace_ext4_writepages(inode, wbc);
+
+	ret = dax_writeback_mapping_range(mapping, inode->i_sb->s_bdev, wbc);
+	trace_ext4_writepages_result(inode, wbc, ret,
+				     nr_to_write - wbc->nr_to_write);
+	percpu_up_read(&sbi->s_journal_flag_rwsem);
+	return ret;
+}
+
 static int ext4_nonda_switch(struct super_block *sb)
 {
 	s64 free_clusters, dirty_clusters;
@@ -3946,6 +3961,13 @@  static const struct address_space_operations ext4_da_aops = {
 	.error_remove_page	= generic_error_remove_page,
 };
 
+static const struct address_space_operations ext4_dax_aops = {
+	.direct_IO		= ext4_direct_IO,
+	.writepages		= ext4_dax_writepages,
+	.set_page_dirty		= noop_set_page_dirty,
+	.invalidatepage		= noop_invalidatepage,
+};
+
 void ext4_set_aops(struct inode *inode)
 {
 	switch (ext4_inode_journal_mode(inode)) {
@@ -3958,7 +3980,9 @@  void ext4_set_aops(struct inode *inode)
 	default:
 		BUG();
 	}
-	if (test_opt(inode->i_sb, DELALLOC))
+	if (IS_DAX(inode))
+		inode->i_mapping->a_ops = &ext4_dax_aops;
+	else if (test_opt(inode->i_sb, DELALLOC))
 		inode->i_mapping->a_ops = &ext4_da_aops;
 	else
 		inode->i_mapping->a_ops = &ext4_aops;