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>

diff --git a/fs/ext2/ext2.h b/fs/ext2/ext2.h
index 23ebb92..28de3ed 100644 (file)
--- a/fs/ext2/ext2.h
+++ b/fs/ext2/ext2.h
@@ -114,6 +114,7 @@ struct ext2_sb_info {
         */
        spinlock_t s_lock;
        struct mb_cache *s_ea_block_cache;
+       struct dax_device *s_daxdev;
 };
 
 static inline spinlock_t *

diff --git a/fs/ext2/inode.c b/fs/ext2/inode.c
index 30163d0..4dca6f3 100644 (file)
--- 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))

diff --git a/fs/ext2/super.c b/fs/ext2/super.c
index 7b1bc90..fc18edd 100644 (file)
--- a/fs/ext2/super.c
+++ b/fs/ext2/super.c
@@ -171,6 +171,7 @@ static void ext2_put_super (struct super_block * sb)
        brelse (sbi->s_sbh);
        sb->s_fs_info = NULL;
        kfree(sbi->s_blockgroup_lock);
+       fs_put_dax(sbi->s_daxdev);
        kfree(sbi);
 }
 
@@ -813,6 +814,7 @@ static unsigned long descriptor_loc(struct super_block *sb,
 
 static int ext2_fill_super(struct super_block *sb, void *data, int silent)
 {
+       struct dax_device *dax_dev = fs_dax_get_by_bdev(sb->s_bdev);
        struct buffer_head * bh;
        struct ext2_sb_info * sbi;
        struct ext2_super_block * es;
@@ -842,6 +844,7 @@ static int ext2_fill_super(struct super_block *sb, void *data, int silent)
        }
        sb->s_fs_info = sbi;
        sbi->s_sb_block = sb_block;
+       sbi->s_daxdev = dax_dev;
 
        spin_lock_init(&sbi->s_lock);
 
@@ -1200,6 +1203,7 @@ failed_sbi:
        kfree(sbi->s_blockgroup_lock);
        kfree(sbi);
 failed:
+       fs_put_dax(dax_dev);
        return ret;
 }