xfs: perform dax_device lookup at mount

The ->iomap_begin() operation is a hot path, so cache the
fs_dax_get_by_host() result at mount time to avoid the incurring the
hash lookup overhead on a per-i/o basis.

Reported-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

6 files changed, 41 insertions, 15 deletions

diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
index 6bf120bb1a17..78185f3b10b2 100644
--- a/fs/xfs/xfs_aops.c
+++ b/fs/xfs/xfs_aops.c
@@ -80,6 +80,19 @@ xfs_find_bdev_for_inode(
                 return mp->m_ddev_targp->bt_bdev;
 }
 
+struct dax_device *
+xfs_find_daxdev_for_inode(
+        struct inode            *inode)
+{
+        struct xfs_inode        *ip = XFS_I(inode);
+        struct xfs_mount        *mp = ip->i_mount;
+
+        if (XFS_IS_REALTIME_INODE(ip))
+                return mp->m_rtdev_targp->bt_daxdev;
+        else
+                return mp->m_ddev_targp->bt_daxdev;
+}
+
 /*
  * We're now finished for good with this page.  Update the page state via the
  * associated buffer_heads, paying attention to the start and end offsets that
diff --git a/fs/xfs/xfs_aops.h b/fs/xfs/xfs_aops.h
index cc174ec6c2fd..88c85ea63da0 100644
--- a/fs/xfs/xfs_aops.h
+++ b/fs/xfs/xfs_aops.h
@@ -59,5 +59,6 @@ int	xfs_setfilesize(struct xfs_inode *ip, xfs_off_t offset, size_t size);
 
 extern void xfs_count_page_state(struct page *, int *, int *);
 extern struct block_device *xfs_find_bdev_for_inode(struct inode *);
+extern struct dax_device *xfs_find_daxdev_for_inode(struct inode *);
 
 #endif /* __XFS_AOPS_H__ */
diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index 72f038492ba8..6deb86c845d1 100644
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -1802,7 +1802,8 @@ xfs_setsize_buftarg_early(
 xfs_buftarg_t *
 xfs_alloc_buftarg(
         struct xfs_mount        *mp,
-        struct block_device     *bdev)
+        struct block_device     *bdev,
+        struct dax_device       *dax_dev)
 {
         xfs_buftarg_t           *btp;
 
@@ -1811,6 +1812,7 @@ xfs_alloc_buftarg(
         btp->bt_mount = mp;
         btp->bt_dev =  bdev->bd_dev;
         btp->bt_bdev = bdev;
+        btp->bt_daxdev = dax_dev;
 
         if (xfs_setsize_buftarg_early(btp, bdev))
                 goto error;
diff --git a/fs/xfs/xfs_buf.h b/fs/xfs/xfs_buf.h
index 20721261dae5..bf71507ddb16 100644
--- a/fs/xfs/xfs_buf.h
+++ b/fs/xfs/xfs_buf.h
@@ -108,6 +108,7 @@ typedef unsigned int xfs_buf_flags_t;
 typedef struct xfs_buftarg {
         dev_t                   bt_dev;
         struct block_device     *bt_bdev;
+        struct dax_device       *bt_daxdev;
         struct xfs_mount        *bt_mount;
         unsigned int            bt_meta_sectorsize;
         size_t                  bt_meta_sectormask;
@@ -385,7 +386,7 @@ xfs_buf_update_cksum(struct xfs_buf *bp, unsigned long cksum_offset)
  *      Handling of buftargs.
  */
 extern xfs_buftarg_t *xfs_alloc_buftarg(struct xfs_mount *,
-                        struct block_device *);
+                        struct block_device *, struct dax_device *);
 extern void xfs_free_buftarg(struct xfs_mount *, struct xfs_buftarg *);
 extern void xfs_wait_buftarg(xfs_buftarg_t *);
 extern int xfs_setsize_buftarg(xfs_buftarg_t *, unsigned int);
diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index 813394c62849..7c934e407332 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -69,6 +69,7 @@ xfs_bmbt_to_iomap(
         iomap->offset = XFS_FSB_TO_B(mp, imap->br_startoff);
         iomap->length = XFS_FSB_TO_B(mp, imap->br_blockcount);
         iomap->bdev = xfs_find_bdev_for_inode(VFS_I(ip));
+        iomap->dax_dev = xfs_find_daxdev_for_inode(VFS_I(ip));
 }
 
 xfs_extlen_t
@@ -976,7 +977,6 @@ xfs_file_iomap_begin(
         int                     nimaps = 1, error = 0;
         bool                    shared = false, trimmed = false;
         unsigned                lockmode;
-        struct block_device     *bdev;
 
         if (XFS_FORCED_SHUTDOWN(mp))
                 return -EIO;
@@ -1087,13 +1087,6 @@ xfs_file_iomap_begin(
 
         xfs_bmbt_to_iomap(ip, iomap, &imap);
 
-        /* optionally associate a dax device with the iomap bdev */
-        bdev = iomap->bdev;
-        if (blk_queue_dax(bdev->bd_queue))
-                iomap->dax_dev = fs_dax_get_by_host(bdev->bd_disk->disk_name);
-        else
-                iomap->dax_dev = NULL;
-
         if (shared)
                 iomap->flags |= IOMAP_F_SHARED;
         return 0;
@@ -1171,7 +1164,6 @@ xfs_file_iomap_end(
         unsigned                flags,
         struct iomap            *iomap)
 {
-        fs_put_dax(iomap->dax_dev);
         if ((flags & IOMAP_WRITE) && iomap->type == IOMAP_DELALLOC)
                 return xfs_file_iomap_end_delalloc(XFS_I(inode), offset,
                                 length, written, iomap);
diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index 38aaacdbb8b3..ee4225c65f0c 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -714,17 +714,26 @@ STATIC void
 xfs_close_devices(
         struct xfs_mount        *mp)
 {
+        struct dax_device *dax_ddev = mp->m_ddev_targp->bt_daxdev;
+
         if (mp->m_logdev_targp && mp->m_logdev_targp != mp->m_ddev_targp) {
                 struct block_device *logdev = mp->m_logdev_targp->bt_bdev;
+                struct dax_device *dax_logdev = mp->m_logdev_targp->bt_daxdev;
+
                 xfs_free_buftarg(mp, mp->m_logdev_targp);
                 xfs_blkdev_put(logdev);
+                fs_put_dax(dax_logdev);
         }
         if (mp->m_rtdev_targp) {
                 struct block_device *rtdev = mp->m_rtdev_targp->bt_bdev;
+                struct dax_device *dax_rtdev = mp->m_rtdev_targp->bt_daxdev;
+
                 xfs_free_buftarg(mp, mp->m_rtdev_targp);
                 xfs_blkdev_put(rtdev);
+                fs_put_dax(dax_rtdev);
         }
         xfs_free_buftarg(mp, mp->m_ddev_targp);
+        fs_put_dax(dax_ddev);
 }
 
 /*
@@ -742,6 +751,8 @@ xfs_open_devices(
         struct xfs_mount        *mp)
 {
         struct block_device     *ddev = mp->m_super->s_bdev;
+        struct dax_device       *dax_ddev = fs_dax_get_by_bdev(ddev);
+        struct dax_device       *dax_logdev = NULL, *dax_rtdev = NULL;
         struct block_device     *logdev = NULL, *rtdev = NULL;
         int                     error;
 
@@ -752,6 +763,7 @@ xfs_open_devices(
                 error = xfs_blkdev_get(mp, mp->m_logname, &logdev);
                 if (error)
                         goto out;
+                dax_logdev = fs_dax_get_by_bdev(logdev);
         }
 
         if (mp->m_rtname) {
@@ -765,24 +777,25 @@ xfs_open_devices(
                         error = -EINVAL;
                         goto out_close_rtdev;
                 }
+                dax_rtdev = fs_dax_get_by_bdev(rtdev);
         }
 
         /*
          * Setup xfs_mount buffer target pointers
          */
         error = -ENOMEM;
-        mp->m_ddev_targp = xfs_alloc_buftarg(mp, ddev);
+        mp->m_ddev_targp = xfs_alloc_buftarg(mp, ddev, dax_ddev);
         if (!mp->m_ddev_targp)
                 goto out_close_rtdev;
 
         if (rtdev) {
-                mp->m_rtdev_targp = xfs_alloc_buftarg(mp, rtdev);
+                mp->m_rtdev_targp = xfs_alloc_buftarg(mp, rtdev, dax_rtdev);
                 if (!mp->m_rtdev_targp)
                         goto out_free_ddev_targ;
         }
 
         if (logdev && logdev != ddev) {
-                mp->m_logdev_targp = xfs_alloc_buftarg(mp, logdev);
+                mp->m_logdev_targp = xfs_alloc_buftarg(mp, logdev, dax_logdev);
                 if (!mp->m_logdev_targp)
                         goto out_free_rtdev_targ;
         } else {
@@ -798,10 +811,14 @@ xfs_open_devices(
         xfs_free_buftarg(mp, mp->m_ddev_targp);
  out_close_rtdev:
         xfs_blkdev_put(rtdev);
+        fs_put_dax(dax_rtdev);
  out_close_logdev:
-        if (logdev && logdev != ddev)
+        if (logdev && logdev != ddev) {
                 xfs_blkdev_put(logdev);
+                fs_put_dax(dax_logdev);
+        }
  out:
+        fs_put_dax(dax_ddev);
         return error;
 }