ext2: 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.

Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Reviewed-by: Jan Kara <jack@suse.cz>
Reported-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

1 files changed, 3 insertions, 8 deletions

diff --git a/fs/ext2/inode.c b/fs/ext2/inode.c
index 30163d007b2f..4dca6f348714 100644
--- a/fs/ext2/inode.c
+++ b/fs/ext2/inode.c
@@ -800,10 +800,10 @@ int ext2_get_block(struct inode *inode, sector_t iblock,
 static int ext2_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
                 unsigned flags, struct iomap *iomap)
 {
-        struct block_device *bdev;
         unsigned int blkbits = inode->i_blkbits;
         unsigned long first_block = offset >> blkbits;
         unsigned long max_blocks = (length + (1 << blkbits) - 1) >> blkbits;
+        struct ext2_sb_info *sbi = EXT2_SB(inode->i_sb);
         bool new = false, boundary = false;
         u32 bno;
         int ret;
@@ -814,13 +814,9 @@ static int ext2_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
                 return ret;
 
         iomap->flags = 0;
-        bdev = inode->i_sb->s_bdev;
-        iomap->bdev = bdev;
+        iomap->bdev = inode->i_sb->s_bdev;
         iomap->offset = (u64)first_block << blkbits;
-        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;
+        iomap->dax_dev = sbi->s_daxdev;
 
         if (ret == 0) {
                 iomap->type = IOMAP_HOLE;
@@ -842,7 +838,6 @@ static int
 ext2_iomap_end(struct inode *inode, loff_t offset, loff_t length,
                 ssize_t written, unsigned flags, struct iomap *iomap)
 {
-        fs_put_dax(iomap->dax_dev);
         if (iomap->type == IOMAP_MAPPED &&
             written < length &&
             (flags & IOMAP_WRITE))