[RFC][PATCH] btrfs: add an autodefrag property

[Josef Bacik <josef@toxicpanda.com>]

Autodefrag is very useful for somethings, like the 9000 sqllite files
that Firefox uses, but is way less useful for virt images.
Unfortunately this is only available currently as a whole mount option.
Fix this by adding an "autodefrag" property, that users can set on a per
file or per directory basis.  Thus allowing them to control where
exactly the extra write activity is going to occur.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
---
- This is an RFC because I want to make sure we're ok with this before I go and
  add btrfs-progs support for this.  I'm not married to the name or the value,
  but I think the core goal is valuable.

 fs/btrfs/btrfs_inode.h |  1 +
 fs/btrfs/file.c        | 16 ++++++++++------
 fs/btrfs/props.c       | 41 +++++++++++++++++++++++++++++++++++++++++
 3 files changed, 52 insertions(+), 6 deletions(-)

diff --git a/fs/btrfs/btrfs_inode.h b/fs/btrfs/btrfs_inode.h
index e7d709505cb1..4f04f0535f90 100644
--- a/fs/btrfs/btrfs_inode.h
+++ b/fs/btrfs/btrfs_inode.h
@@ -31,6 +31,7 @@ enum {
 	BTRFS_INODE_READDIO_NEED_LOCK,
 	BTRFS_INODE_HAS_PROPS,
 	BTRFS_INODE_SNAPSHOT_FLUSH,
+	BTRFS_INODE_AUTODEFRAG,
 };
 
 /* in memory btrfs inode */
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 841c516079a9..cac2092bdcdf 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -116,12 +116,16 @@ static int __btrfs_add_inode_defrag(struct btrfs_inode *inode,
 	return 0;
 }
 
-static inline int __need_auto_defrag(struct btrfs_fs_info *fs_info)
+static inline int __need_auto_defrag(struct btrfs_fs_info *fs_info,
+				     struct btrfs_inode *inode)
 {
-	if (!btrfs_test_opt(fs_info, AUTO_DEFRAG))
+	if (btrfs_fs_closing(fs_info))
 		return 0;
 
-	if (btrfs_fs_closing(fs_info))
+	if (inode && test_bit(BTRFS_INODE_AUTODEFRAG, &inode->runtime_flags))
+		return 1;
+
+	if (!btrfs_test_opt(fs_info, AUTO_DEFRAG))
 		return 0;
 
 	return 1;
@@ -140,7 +144,7 @@ int btrfs_add_inode_defrag(struct btrfs_trans_handle *trans,
 	u64 transid;
 	int ret;
 
-	if (!__need_auto_defrag(fs_info))
+	if (!__need_auto_defrag(fs_info, inode))
 		return 0;
 
 	if (test_bit(BTRFS_INODE_IN_DEFRAG, &inode->runtime_flags))
@@ -187,7 +191,7 @@ static void btrfs_requeue_inode_defrag(struct btrfs_inode *inode,
 	struct btrfs_fs_info *fs_info = inode->root->fs_info;
 	int ret;
 
-	if (!__need_auto_defrag(fs_info))
+	if (!__need_auto_defrag(fs_info, inode))
 		goto out;
 
 	/*
@@ -348,7 +352,7 @@ int btrfs_run_defrag_inodes(struct btrfs_fs_info *fs_info)
 			     &fs_info->fs_state))
 			break;
 
-		if (!__need_auto_defrag(fs_info))
+		if (btrfs_fs_closing(fs_info))
 			break;
 
 		/* find an inode to defrag */
diff --git a/fs/btrfs/props.c b/fs/btrfs/props.c
index 2dcb1cb21634..5c6411c8b19f 100644
--- a/fs/btrfs/props.c
+++ b/fs/btrfs/props.c
@@ -310,6 +310,40 @@ static const char *prop_compression_extract(struct inode *inode)
 	return NULL;
 }
 
+static int prop_autodefrag_validate(const char *value, size_t len)
+{
+	if (!value)
+		return 0;
+	if (!strncmp("true", value, 4))
+		return 0;
+	return -EINVAL;
+}
+
+static int prop_autodefrag_apply(struct inode *inode, const char *value,
+				 size_t len)
+{
+	if (len == 0) {
+		clear_bit(BTRFS_INODE_AUTODEFRAG,
+			  &BTRFS_I(inode)->runtime_flags);
+		return 0;
+	}
+
+	if (!strncmp("true", value, 4)) {
+		set_bit(BTRFS_INODE_AUTODEFRAG,
+			&BTRFS_I(inode)->runtime_flags);
+		return 0;
+	}
+
+	return -EINVAL;
+}
+
+static const char *prop_autodefrag_extract(struct inode *inode)
+{
+	if (test_bit(BTRFS_INODE_AUTODEFRAG, &BTRFS_I(inode)->runtime_flags))
+		return "true";
+	return NULL;
+}
+
 static struct prop_handler prop_handlers[] = {
 	{
 		.xattr_name = XATTR_BTRFS_PREFIX "compression",
@@ -318,6 +352,13 @@ static struct prop_handler prop_handlers[] = {
 		.extract = prop_compression_extract,
 		.inheritable = 1
 	},
+	{
+		.xattr_name = XATTR_BTRFS_PREFIX "autodefrag",
+		.validate = prop_autodefrag_validate,
+		.apply = prop_autodefrag_apply,
+		.extract = prop_autodefrag_extract,
+		.inheritable = 1
+	},
 };
 
 static int inherit_props(struct btrfs_trans_handle *trans,
-- 
2.24.1