[PATCH, RFC 3/3] ext4: use the O_HOT and O_COLD open flags to influence inode allocation

[Theodore Ts'o <tytso@mit.edu>]

Wire up the use of the O_HOT and O_COLD open flags so that when an
inode is being created, it can influence which part of the disk gets
used on rotational storage devices.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
---
 fs/ext4/ext4.h    |    8 +++++++-
 fs/ext4/ialloc.c  |   33 +++++++++++++++++++++++++++------
 fs/ext4/migrate.c |    2 +-
 fs/ext4/namei.c   |   15 +++++++++++----
 4 files changed, 46 insertions(+), 12 deletions(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 0e01e90..6539c9a 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1553,6 +1553,12 @@ struct ext4_dir_entry_2 {
 #define EXT4_MAX_REC_LEN		((1<<16)-1)
 
 /*
+ * Flags for ext4_new_inode()
+ */
+#define EXT4_NEWI_HOT	0x0001
+#define EXT4_NEWI_COLD	0x0002
+
+/*
  * If we ever get support for fs block sizes > page_size, we'll need
  * to remove the #if statements in the next two functions...
  */
@@ -1850,7 +1856,7 @@ extern int ext4fs_dirhash(const char *name, int len, struct
 /* ialloc.c */
 extern struct inode *ext4_new_inode(handle_t *, struct inode *, umode_t,
 				    const struct qstr *qstr, __u32 goal,
-				    uid_t *owner);
+				    uid_t *owner, int flags);
 extern void ext4_free_inode(handle_t *, struct inode *);
 extern struct inode * ext4_orphan_get(struct super_block *, unsigned long);
 extern unsigned long ext4_count_free_inodes(struct super_block *);
diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
index 409c2ee..3dcc8c8 100644
--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c
@@ -363,7 +363,7 @@ static void get_orlov_stats(struct super_block *sb, ext4_group_t g,
 
 static int find_group_orlov(struct super_block *sb, struct inode *parent,
 			    ext4_group_t *group, umode_t mode,
-			    const struct qstr *qstr)
+			    const struct qstr *qstr, int flags)
 {
 	ext4_group_t parent_group = EXT4_I(parent)->i_block_group;
 	struct ext4_sb_info *sbi = EXT4_SB(sb);
@@ -508,13 +508,20 @@ fallback_retry:
 }
 
 static int find_group_other(struct super_block *sb, struct inode *parent,
-			    ext4_group_t *group, umode_t mode)
+			    ext4_group_t *group, umode_t mode, int flags)
 {
 	ext4_group_t parent_group = EXT4_I(parent)->i_block_group;
 	ext4_group_t i, last, ngroups = ext4_get_groups_count(sb);
 	struct ext4_group_desc *desc;
 	int flex_size = ext4_flex_bg_size(EXT4_SB(sb));
 
+	if ((flags & EXT4_NEWI_HOT) && (ngroups > 3) &&
+	    (parent_group > ngroups / 3))
+		parent_group = 0;
+	if ((flags & EXT4_NEWI_COLD) && (ngroups > 3) &&
+	    (parent_group < (2 * (ngroups / 3))))
+		parent_group = 2 * (ngroups / 3);
+
 	/*
 	 * Try to place the inode is the same flex group as its
 	 * parent.  If we can't find space, use the Orlov algorithm to
@@ -550,7 +557,7 @@ static int find_group_other(struct super_block *sb, struct inode *parent,
 		*group = parent_group + flex_size;
 		if (*group > ngroups)
 			*group = 0;
-		return find_group_orlov(sb, parent, group, mode, NULL);
+		return find_group_orlov(sb, parent, group, mode, NULL, flags);
 	}
 
 	/*
@@ -614,7 +621,8 @@ static int find_group_other(struct super_block *sb, struct inode *parent,
  * group to find a free inode.
  */
 struct inode *ext4_new_inode(handle_t *handle, struct inode *dir, umode_t mode,
-			     const struct qstr *qstr, __u32 goal, uid_t *owner)
+			     const struct qstr *qstr, __u32 goal, uid_t *owner,
+			     int flags)
 {
 	struct super_block *sb;
 	struct buffer_head *inode_bitmap_bh = NULL;
@@ -643,6 +651,19 @@ struct inode *ext4_new_inode(handle_t *handle, struct inode *dir, umode_t mode,
 	ei = EXT4_I(inode);
 	sbi = EXT4_SB(sb);
 
+	if (blk_queue_nonrot(bdev_get_queue(sb->s_bdev)))
+		flags &= ~(EXT4_NEWI_HOT | EXT4_NEWI_COLD);
+
+	/* 
+	 * We will only allow the HOT flag if the user passes the
+	 * reserved uid/gid check, or if she has CAP_SYS_RESOURCE
+	 */
+	if ((flags & EXT4_NEWI_HOT) && 
+	    !(sbi->s_resuid == current_fsuid() ||
+	      ((sbi->s_resgid != 0) && in_group_p(sbi->s_resgid)) ||
+	      capable(CAP_SYS_RESOURCE)))
+		flags &= ~EXT4_NEWI_HOT;
+
 	if (!goal)
 		goal = sbi->s_inode_goal;
 
@@ -654,9 +675,9 @@ struct inode *ext4_new_inode(handle_t *handle, struct inode *dir, umode_t mode,
 	}
 
 	if (S_ISDIR(mode))
-		ret2 = find_group_orlov(sb, dir, &group, mode, qstr);
+		ret2 = find_group_orlov(sb, dir, &group, mode, qstr, flags);
 	else
-		ret2 = find_group_other(sb, dir, &group, mode);
+		ret2 = find_group_other(sb, dir, &group, mode, flags);
 
 got_group:
 	EXT4_I(dir)->i_last_alloc_group = group;
diff --git a/fs/ext4/migrate.c b/fs/ext4/migrate.c
index f39f80f..2b3d65c 100644
--- a/fs/ext4/migrate.c
+++ b/fs/ext4/migrate.c
@@ -469,7 +469,7 @@ int ext4_ext_migrate(struct inode *inode)
 	owner[0] = inode->i_uid;
 	owner[1] = inode->i_gid;
 	tmp_inode = ext4_new_inode(handle, inode->i_sb->s_root->d_inode,
-				   S_IFREG, NULL, goal, owner);
+				   S_IFREG, NULL, goal, owner, 0);
 	if (IS_ERR(tmp_inode)) {
 		retval = PTR_ERR(tmp_inode);
 		ext4_journal_stop(handle);
diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index 6f48ff8..222a419 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -1742,6 +1742,7 @@ static int ext4_create(struct inode *dir, struct dentry *dentry, umode_t mode,
 	handle_t *handle;
 	struct inode *inode;
 	int err, retries = 0;
+	int flags = 0;
 
 	dquot_initialize(dir);
 
@@ -1755,7 +1756,13 @@ retry:
 	if (IS_DIRSYNC(dir))
 		ext4_handle_sync(handle);
 
-	inode = ext4_new_inode(handle, dir, mode, &dentry->d_name, 0, NULL);
+	if (op && op->open_flag & O_HOT)
+		flags |= EXT4_NEWI_HOT;
+	if (op && op->open_flag & O_COLD)
+		flags |= EXT4_NEWI_COLD;
+
+	inode = ext4_new_inode(handle, dir, mode, &dentry->d_name, 0,
+			       NULL, flags);
 	err = PTR_ERR(inode);
 	if (!IS_ERR(inode)) {
 		inode->i_op = &ext4_file_inode_operations;
@@ -1791,7 +1798,7 @@ retry:
 	if (IS_DIRSYNC(dir))
 		ext4_handle_sync(handle);
 
-	inode = ext4_new_inode(handle, dir, mode, &dentry->d_name, 0, NULL);
+	inode = ext4_new_inode(handle, dir, mode, &dentry->d_name, 0, NULL, 0);
 	err = PTR_ERR(inode);
 	if (!IS_ERR(inode)) {
 		init_special_inode(inode, inode->i_mode, rdev);
@@ -1831,7 +1838,7 @@ retry:
 		ext4_handle_sync(handle);
 
 	inode = ext4_new_inode(handle, dir, S_IFDIR | mode,
-			       &dentry->d_name, 0, NULL);
+			       &dentry->d_name, 0, NULL, 0);
 	err = PTR_ERR(inode);
 	if (IS_ERR(inode))
 		goto out_stop;
@@ -2278,7 +2285,7 @@ retry:
 		ext4_handle_sync(handle);
 
 	inode = ext4_new_inode(handle, dir, S_IFLNK|S_IRWXUGO,
-			       &dentry->d_name, 0, NULL);
+			       &dentry->d_name, 0, NULL, 0);
 	err = PTR_ERR(inode);
 	if (IS_ERR(inode))
 		goto out_stop;
-- 
1.7.10.rc3