ext4: 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/ext4/ext4.h b/fs/ext4/ext4.h
index a2bb7d2870e487de3f8601107cdf67c05b022034..194e622dc3dd942b37b460d4c49405aa64083c3c 100644 (file)
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1528,6 +1528,7 @@ struct ext4_sb_info {
 
        /* Barrier between changing inodes' journal flags and writepages ops. */
        struct percpu_rw_semaphore s_journal_flag_rwsem;
+       struct dax_device *s_daxdev;
 };
 
 static inline struct ext4_sb_info *EXT4_SB(struct super_block *sb)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index c774bdc22759b1602341da70a0b3fec7b8830f2c..16424b5c4e885b7d9f075cd4c850e8bda0cf5394 100644 (file)
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3404,7 +3404,7 @@ static int ext4_releasepage(struct page *page, gfp_t wait)
 static int ext4_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
                            unsigned flags, struct iomap *iomap)
 {
-       struct block_device *bdev;
+       struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
        unsigned int blkbits = inode->i_blkbits;
        unsigned long first_block = offset >> blkbits;
        unsigned long last_block = (offset + length - 1) >> blkbits;
@@ -3473,12 +3473,8 @@ retry:
        }
 
        iomap->flags = 0;
-       bdev = inode->i_sb->s_bdev;
-       iomap->bdev = 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;
+       iomap->bdev = inode->i_sb->s_bdev;
+       iomap->dax_dev = sbi->s_daxdev;
        iomap->offset = first_block << blkbits;
 
        if (ret == 0) {
@@ -3511,7 +3507,6 @@ static int ext4_iomap_end(struct inode *inode, loff_t offset, loff_t length,
        int blkbits = inode->i_blkbits;
        bool truncate = false;
 
-       fs_put_dax(iomap->dax_dev);
        if (!(flags & IOMAP_WRITE) || (flags & IOMAP_FAULT))
                return 0;
 

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index d61a70e2193a012d48f5c56140a416abb2280b68..3e58f952eddc0b45be3ade8fdba3df0189bda076 100644 (file)
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -951,6 +951,7 @@ static void ext4_put_super(struct super_block *sb)
        if (sbi->s_chksum_driver)
                crypto_free_shash(sbi->s_chksum_driver);
        kfree(sbi->s_blockgroup_lock);
+       fs_put_dax(sbi->s_daxdev);
        kfree(sbi);
 }
 
@@ -3377,6 +3378,7 @@ static void ext4_set_resv_clusters(struct super_block *sb)
 
 static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 {
+       struct dax_device *dax_dev = fs_dax_get_by_bdev(sb->s_bdev);
        char *orig_data = kstrdup(data, GFP_KERNEL);
        struct buffer_head *bh;
        struct ext4_super_block *es = NULL;
@@ -3399,6 +3401,7 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
        unsigned int journal_ioprio = DEFAULT_JOURNAL_IOPRIO;
        ext4_group_t first_not_zeroed;
 
+       sbi->s_daxdev = dax_dev;
        if ((data && !orig_data) || !sbi)
                goto out_free_base;
 
@@ -4378,6 +4381,7 @@ out_fail:
 out_free_base:
        kfree(sbi);
        kfree(orig_data);
+       fs_put_dax(dax_dev);
        return err ? err : ret;
 }