[Cluster-devel] [GFS2 PATCH] GFS2: Add function gfs2_get_iomap

[Bob Peterson <rpeterso@redhat.com>]

Hi,

This patch replaces the GFS2 fiemap implementation that used vfs
function __generic_block_fiemap with a new implementation that uses
the new iomap-based fiemap interface. This allows GFS2's fiemap to
skip holes. The time to do filefrag on a file with a 1 petabyte hole
is reduced from several days or weeks, to milliseconds. Note that
there are Kconfig changes that affect everyone.

Signed-off-by: Bob Peterson <rpeterso@redhat.com>
---
diff --git a/fs/Kconfig b/fs/Kconfig
index 2bc7ad7..d601aeb 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -11,7 +11,7 @@ config DCACHE_WORD_ACCESS
 if BLOCK
 
 config FS_IOMAP
-	bool
+	bool "File System IOMAP Support"
 
 source "fs/ext2/Kconfig"
 source "fs/ext4/Kconfig"
diff --git a/fs/gfs2/Kconfig b/fs/gfs2/Kconfig
index 90c6a8f..f8fa955 100644
--- a/fs/gfs2/Kconfig
+++ b/fs/gfs2/Kconfig
@@ -25,6 +25,7 @@ config GFS2_FS
 config GFS2_FS_LOCKING_DLM
 	bool "GFS2 DLM locking"
 	depends on (GFS2_FS!=n) && NET && INET && (IPV6 || IPV6=n) && \
+		FS_IOMAP && \
 		CONFIGFS_FS && SYSFS && (DLM=y || DLM=GFS2_FS)
 	help
 	  Multiple node locking module for GFS2
diff --git a/fs/gfs2/bmap.c b/fs/gfs2/bmap.c
index 6e2bec1..685f1ed 100644
--- a/fs/gfs2/bmap.c
+++ b/fs/gfs2/bmap.c
@@ -588,6 +588,155 @@ static int gfs2_bmap_alloc(struct inode *inode, const sector_t lblock,
 }
 
 /**
+ * hole_size - figure out the size of a hole
+ * @ip: The inode
+ * @lblock: The logical starting block number
+ * @mp: The metapath
+ *
+ * Returns: The hole size in bytes
+ *
+ */
+static u64 hole_size(struct inode *inode, sector_t lblock, struct metapath *mp)
+{
+	struct gfs2_inode *ip = GFS2_I(inode);
+	struct gfs2_sbd *sdp = GFS2_SB(inode);
+	struct metapath mp_eof;
+	unsigned int end_of_metadata = ip->i_height - 1;
+	u64 factor = 1;
+	int hgt = end_of_metadata;
+	u64 holesz = 0, holestep;
+	const __be64 *first, *end, *ptr;
+	const struct buffer_head *bh;
+	u64 isize = i_size_read(inode);
+	int zeroptrs;
+	bool done = false;
+
+	/* Get another metapath, to the very last byte */
+	find_metapath(sdp, (isize - 1) >> inode->i_blkbits, &mp_eof,
+		      ip->i_height);
+	for (hgt = end_of_metadata; hgt >= 0 && !done; hgt--) {
+		bh = mp->mp_bh[hgt];
+		if (bh) {
+			zeroptrs = 0;
+			first = metapointer(hgt, mp);
+			end = (const __be64 *)(bh->b_data + bh->b_size);
+
+			for (ptr = first; ptr < end; ptr++) {
+				if (*ptr) {
+					done = true;
+					break;
+				} else {
+					zeroptrs++;
+				}
+			}
+		} else {
+			zeroptrs = sdp->sd_inptrs;
+		}
+		holestep = min(factor * zeroptrs,
+			       isize - (lblock + (zeroptrs * holesz)));
+		holesz += holestep;
+		if (lblock + holesz >= isize)
+			return holesz << inode->i_blkbits;
+
+		factor *= sdp->sd_inptrs;
+		if (hgt && (mp->mp_list[hgt - 1] < mp_eof.mp_list[hgt - 1]))
+			(mp->mp_list[hgt - 1])++;
+	}
+	return holesz << inode->i_blkbits;
+}
+
+/**
+ * gfs2_get_iomap - Map blocks from an inode to disk blocks
+ * @mapping: The address space
+ * @pos: Starting position in bytes
+ * @length: Length to map, in bytes
+ * @iomap: The iomap structure
+ *
+ * Returns: errno
+ */
+
+int gfs2_get_iomap(struct inode *inode, loff_t pos, ssize_t length,
+		   struct iomap *iomap)
+{
+	struct gfs2_inode *ip = GFS2_I(inode);
+	struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
+	unsigned int bsize = sdp->sd_sb.sb_bsize;
+	const u64 *arr = sdp->sd_heightsize;
+	__be64 *ptr;
+	sector_t lblock = pos >> sdp->sd_sb.sb_bsize_shift;
+	u64 size;
+	struct metapath mp;
+	int ret, eob;
+	unsigned int len;
+	struct buffer_head *bh;
+	u8 height;
+	loff_t isize = i_size_read(inode);
+
+	if (length == 0)
+		return -EINVAL;
+
+	iomap->offset = pos;
+	iomap->blkno = 0;
+	iomap->type = IOMAP_HOLE;
+	iomap->length = length;
+
+	if (pos >= isize)
+		return 0;
+
+	memset(mp.mp_bh, 0, sizeof(mp.mp_bh));
+	bmap_lock(ip, 0);
+	if (gfs2_is_dir(ip)) {
+		bsize = sdp->sd_jbsize;
+		arr = sdp->sd_jheightsize;
+	}
+
+	ret = gfs2_meta_inode_buffer(ip, &mp.mp_bh[0]);
+	if (ret)
+		goto out_release;
+
+	height = ip->i_height;
+	size = (lblock + 1) * bsize;
+	while (size > arr[height])
+		height++;
+	find_metapath(sdp, lblock, &mp, height);
+	if (height > ip->i_height || gfs2_is_stuffed(ip)) {
+		ret = -EINVAL;
+		goto out_release;
+	}
+	ret = lookup_metapath(ip, &mp);
+	if (ret < 0)
+		goto out_release;
+
+	if (ret != ip->i_height) {
+		iomap->length = hole_size(inode, lblock, &mp);
+		goto out_meta_hole;
+	}
+
+	ptr = metapointer(ip->i_height - 1, &mp);
+	iomap->blkno = be64_to_cpu(*ptr);
+	if (*ptr)
+		iomap->type = IOMAP_MAPPED;
+	else
+		iomap->type = IOMAP_HOLE;
+
+	bh = mp.mp_bh[ip->i_height - 1];
+	len = gfs2_extent_length(bh->b_data, bh->b_size, ptr,
+				 length >> inode->i_blkbits, &eob);
+	iomap->length = len << sdp->sd_sb.sb_bsize_shift;
+	/* If we go past eof, round up to the nearest block */
+	if (iomap->offset + iomap->length >= isize)
+		iomap->length = (((isize - iomap->offset) + (bsize - 1)) &
+				 ~(bsize - 1));
+
+out_meta_hole:
+	ret = 0;
+out_release:
+	release_metapath(&mp);
+	bmap_unlock(ip, 0);
+	return ret;
+}
+
+/**
  * gfs2_block_map - Map a block from an inode to a disk block
  * @inode: The inode
  * @lblock: The logical block number
diff --git a/fs/gfs2/bmap.h b/fs/gfs2/bmap.h
index 81ded5e..8da2429 100644
--- a/fs/gfs2/bmap.h
+++ b/fs/gfs2/bmap.h
@@ -10,6 +10,8 @@
 #ifndef __BMAP_DOT_H__
 #define __BMAP_DOT_H__
 
+#include <linux/iomap.h>
+
 #include "inode.h"
 
 struct inode;
@@ -47,6 +49,8 @@ static inline void gfs2_write_calc_reserv(const struct gfs2_inode *ip,
 extern int gfs2_unstuff_dinode(struct gfs2_inode *ip, struct page *page);
 extern int gfs2_block_map(struct inode *inode, sector_t lblock,
 			  struct buffer_head *bh, int create);
+extern int gfs2_get_iomap(struct inode *inode, loff_t pos,
+			  ssize_t length, struct iomap *iomap);
 extern int gfs2_extent_map(struct inode *inode, u64 lblock, int *new,
 			   u64 *dblock, unsigned *extlen);
 extern int gfs2_setattr_size(struct inode *inode, u64 size);
diff --git a/fs/gfs2/inode.c b/fs/gfs2/inode.c
index e4da0ec..0d705ef 100644
--- a/fs/gfs2/inode.c
+++ b/fs/gfs2/inode.c
@@ -17,7 +17,7 @@
 #include <linux/posix_acl.h>
 #include <linux/gfs2_ondisk.h>
 #include <linux/crc32.h>
-#include <linux/fiemap.h>
+#include <linux/iomap.h>
 #include <linux/security.h>
 #include <asm/uaccess.h>
 
@@ -1990,28 +1990,65 @@ static int gfs2_getattr(struct vfsmount *mnt, struct dentry *dentry,
 	return 0;
 }
 
+static int gfs2_iomap_fiemap_begin(struct inode *inode, loff_t offset,
+				   loff_t length, unsigned flags,
+				   struct iomap *iomap)
+{
+	struct gfs2_inode *ip = GFS2_I(inode);
+	struct gfs2_holder *gh;
+	int ret;
+
+	gh = kzalloc(sizeof(struct gfs2_holder), GFP_NOFS);
+	if (!gh)
+		return -ENOMEM;
+
+	ret = gfs2_glock_nq_init(ip->i_gl, LM_ST_SHARED, 0, gh);
+	if (ret) {
+		kfree(gh);
+		return ret;
+	}
+	ret = gfs2_get_iomap(inode, offset, length, iomap);
+	if (ret)
+		gfs2_glock_dq_uninit(gh);
+	return ret;
+}
+
+static int gfs2_iomap_fiemap_end(struct inode *inode, loff_t offset,
+				 loff_t length, ssize_t written,
+				 unsigned flags, struct iomap *iomap)
+{
+	struct gfs2_inode *ip = GFS2_I(inode);
+	struct gfs2_holder *gh;
+
+	gh = gfs2_glock_is_locked_by_me(ip->i_gl);
+	BUG_ON(gh == NULL);
+	gfs2_glock_dq_uninit(gh);
+	return 0;
+}
+
 static int gfs2_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
 		       u64 start, u64 len)
 {
 	struct gfs2_inode *ip = GFS2_I(inode);
-	struct gfs2_holder gh;
 	int ret;
+	struct iomap_ops gfs2_iomap_fiemap_ops = {
+		.iomap_begin = gfs2_iomap_fiemap_begin,
+		.iomap_end = gfs2_iomap_fiemap_end,
+	};
 
-	ret = fiemap_check_flags(fieinfo, FIEMAP_FLAG_SYNC);
-	if (ret)
-		return ret;
 
 	inode_lock(inode);
 
-	ret = gfs2_glock_nq_init(ip->i_gl, LM_ST_SHARED, 0, &gh);
-	if (ret)
-		goto out;
-
 	if (gfs2_is_stuffed(ip)) {
+		struct gfs2_holder gh;
 		u64 phys = ip->i_no_addr << inode->i_blkbits;
 		u64 size = i_size_read(inode);
 		u32 flags = FIEMAP_EXTENT_LAST|FIEMAP_EXTENT_NOT_ALIGNED|
 			    FIEMAP_EXTENT_DATA_INLINE;
+		ret = gfs2_glock_nq_init(ip->i_gl, LM_ST_SHARED, 0, &gh);
+		if (ret)
+			goto out;
+
 		phys += sizeof(struct gfs2_dinode);
 		phys += start;
 		if (start + len > size)
@@ -2021,12 +2058,12 @@ static int gfs2_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
 						      len, flags);
 		if (ret == 1)
 			ret = 0;
+		gfs2_glock_dq_uninit(&gh);
 	} else {
-		ret = __generic_block_fiemap(inode, fieinfo, start, len,
-					     gfs2_block_map);
+		ret = iomap_fiemap(inode, fieinfo, start, len,
+				   &gfs2_iomap_fiemap_ops);
 	}
 
-	gfs2_glock_dq_uninit(&gh);
 out:
 	inode_unlock(inode);
 	return ret;