xfs: add initial DAX support

Add initial DAX support to XFS. To do this we need a new mount
option to turn DAX on filesystem, and we need to propagate this into
the inode flags whenever an inode is instantiated so that the
per-inode checks throughout the code Do The Right Thing.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

3 files changed, 37 insertions, 14 deletions

diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
index 0994f95c368f..3e8d32d41f35 100644
--- a/fs/xfs/xfs_iops.c
+++ b/fs/xfs/xfs_iops.c
@@ -1195,22 +1195,22 @@ xfs_diflags_to_iflags(
         struct inode            *inode,
         struct xfs_inode        *ip)
 {
-        if (ip->i_d.di_flags & XFS_DIFLAG_IMMUTABLE)
+        uint16_t                flags = ip->i_d.di_flags;
+
+        inode->i_flags &= ~(S_IMMUTABLE | S_APPEND | S_SYNC |
+                            S_NOATIME | S_DAX);
+
+        if (flags & XFS_DIFLAG_IMMUTABLE)
                 inode->i_flags |= S_IMMUTABLE;
-        else
-                inode->i_flags &= ~S_IMMUTABLE;
-        if (ip->i_d.di_flags & XFS_DIFLAG_APPEND)
+        if (flags & XFS_DIFLAG_APPEND)
                 inode->i_flags |= S_APPEND;
-        else
-                inode->i_flags &= ~S_APPEND;
-        if (ip->i_d.di_flags & XFS_DIFLAG_SYNC)
+        if (flags & XFS_DIFLAG_SYNC)
                 inode->i_flags |= S_SYNC;
-        else
-                inode->i_flags &= ~S_SYNC;
-        if (ip->i_d.di_flags & XFS_DIFLAG_NOATIME)
+        if (flags & XFS_DIFLAG_NOATIME)
                 inode->i_flags |= S_NOATIME;
-        else
-                inode->i_flags &= ~S_NOATIME;
+        /* XXX: Also needs an on-disk per inode flag! */
+        if (ip->i_mount->m_flags & XFS_MOUNT_DAX)
+                inode->i_flags |= S_DAX;
 }
 
 /*
diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
index 8c995a2ccb6f..cd44e88efa53 100644
--- a/fs/xfs/xfs_mount.h
+++ b/fs/xfs/xfs_mount.h
@@ -179,6 +179,8 @@ typedef struct xfs_mount {
                                                    allocator */
 #define XFS_MOUNT_NOATTR2       (1ULL << 25)    /* disable use of attr2 format */
 
+#define XFS_MOUNT_DAX           (1ULL << 62)    /* TEST ONLY! */
+
 
 /*
  * Default minimum read and write sizes.
diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index 858e1e62bbaa..1fb16562c159 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -112,6 +112,8 @@ static struct xfs_kobj xfs_dbg_kobj;	/* global debug sysfs attrs */
 #define MNTOPT_DISCARD     "discard"    /* Discard unused blocks */
 #define MNTOPT_NODISCARD   "nodiscard"  /* Do not discard unused blocks */
 
+#define MNTOPT_DAX      "dax"           /* Enable direct access to bdev pages */
+
 /*
  * Table driven mount option parser.
  *
@@ -363,6 +365,10 @@ xfs_parseargs(
                         mp->m_flags |= XFS_MOUNT_DISCARD;
                 } else if (!strcmp(this_char, MNTOPT_NODISCARD)) {
                         mp->m_flags &= ~XFS_MOUNT_DISCARD;
+#ifdef CONFIG_FS_DAX
+                } else if (!strcmp(this_char, MNTOPT_DAX)) {
+                        mp->m_flags |= XFS_MOUNT_DAX;
+#endif
                 } else {
                         xfs_warn(mp, "unknown mount option [%s].", this_char);
                         return -EINVAL;
@@ -452,8 +458,8 @@ done:
 }
 
 struct proc_xfs_info {
-        int     flag;
-        char    *str;
+        uint64_t        flag;
+        char            *str;
 };
 
 STATIC int
@@ -474,6 +480,7 @@ xfs_showargs(
                 { XFS_MOUNT_GRPID,              "," MNTOPT_GRPID },
                 { XFS_MOUNT_DISCARD,            "," MNTOPT_DISCARD },
                 { XFS_MOUNT_SMALL_INUMS,        "," MNTOPT_32BITINODE },
+                { XFS_MOUNT_DAX,                "," MNTOPT_DAX },
                 { 0, NULL }
         };
         static struct proc_xfs_info xfs_info_unset[] = {
@@ -1507,6 +1514,20 @@ xfs_fs_fill_super(
         if (XFS_SB_VERSION_NUM(&mp->m_sb) == XFS_SB_VERSION_5)
                 sb->s_flags |= MS_I_VERSION;
 
+        if (mp->m_flags & XFS_MOUNT_DAX) {
+                xfs_warn(mp,
+        "DAX enabled. Warning: EXPERIMENTAL, use at your own risk");
+                if (sb->s_blocksize != PAGE_SIZE) {
+                        xfs_alert(mp,
+                "Filesystem block size invalid for DAX Turning DAX off.");
+                        mp->m_flags &= ~XFS_MOUNT_DAX;
+                } else if (!sb->s_bdev->bd_disk->fops->direct_access) {
+                        xfs_alert(mp,
+                "Block device does not support DAX Turning DAX off.");
+                        mp->m_flags &= ~XFS_MOUNT_DAX;
+                }
+        }
+
         error = xfs_mountfs(mp);
         if (error)
                 goto out_filestream_unmount;