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Subject[PATCH 1/2] xfs: cache dax_device lookup result
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The ->iomap_begin() operation is a hot path, so cache the
fs_dax_get_by_host() result to avoid the incurring the hash lookup
overhead.

Cc: "Darrick J. Wong" <darrick.wong@oracle.com>
Reported-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
fs/xfs/xfs_aops.c | 24 ++++++++++++++++++++++++
fs/xfs/xfs_aops.h | 1 +
fs/xfs/xfs_buf.h | 1 +
fs/xfs/xfs_iomap.c | 9 +--------
4 files changed, 27 insertions(+), 8 deletions(-)

diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
index 6bf120bb1a17..d16e013e1b8c 100644
--- a/fs/xfs/xfs_aops.c
+++ b/fs/xfs/xfs_aops.c
@@ -80,6 +80,30 @@ 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;
+ struct block_device *bdev;
+ xfs_buftarg_t *bt;
+
+ if (XFS_IS_REALTIME_INODE(ip))
+ bt = mp->m_rtdev_targp;
+ else
+ bt = mp->m_ddev_targp;
+
+ bdev = bt->bt_bdev;
+ if (!blk_queue_dax(bdev->bd_queue))
+ return NULL;
+
+ if (!bt->bt_daxdev)
+ bt->bt_daxdev = fs_dax_get_by_host(bdev->bd_disk->disk_name);
+
+ return bt->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.h b/fs/xfs/xfs_buf.h
index 20721261dae5..fc95a02f272a 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;
diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index 813394c62849..3e8b9ec9e802 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;
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