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From: Andreas Gruenbacher <agruenba@redhat.com>
To: cluster-devel@redhat.com, Christoph Hellwig <hch@lst.de>
Cc: linux-fsdevel@vger.kernel.org, Andreas Gruenbacher <agruenba@redhat.com>
Subject: [PATCH v4 02/11] gfs2: hole_size improvement
Date: Mon, 14 May 2018 17:36:15 +0200	[thread overview]
Message-ID: <20180514153624.29598-3-agruenba@redhat.com> (raw)
In-Reply-To: <20180514153624.29598-1-agruenba@redhat.com>

Reimplement function hole_size based on a generic function for walking
the metadata tree and rename hole_size to gfs2_hole_size.  While
previously, multiple invocations of hole_size were sometimes needed to
walk across the entire hole, the new implementation always returns the
entire hole at once (provided that the caller is interested in the total
size).

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
---
 fs/gfs2/bmap.c | 187 +++++++++++++++++++++++++++++++++++++------------
 1 file changed, 141 insertions(+), 46 deletions(-)

diff --git a/fs/gfs2/bmap.c b/fs/gfs2/bmap.c
index fcf2f7d166de..a8efc887ab69 100644
--- a/fs/gfs2/bmap.c
+++ b/fs/gfs2/bmap.c
@@ -278,6 +278,21 @@ static inline __be64 *metapointer(unsigned int height, const struct metapath *mp
 	return p + mp->mp_list[height];
 }
 
+static inline const __be64 *metaend(unsigned int height, const struct metapath *mp)
+{
+	const struct buffer_head *bh = mp->mp_bh[height];
+	return (const __be64 *)(bh->b_data + bh->b_size);
+}
+
+static void clone_metapath(struct metapath *clone, struct metapath *mp)
+{
+	unsigned int hgt;
+
+	*clone = *mp;
+	for (hgt = 0; hgt < mp->mp_aheight; hgt++)
+		get_bh(clone->mp_bh[hgt]);
+}
+
 static void gfs2_metapath_ra(struct gfs2_glock *gl, __be64 *start, __be64 *end)
 {
 	const __be64 *t;
@@ -615,60 +630,140 @@ static int gfs2_iomap_alloc(struct inode *inode, struct iomap *iomap,
 	return 0;
 }
 
-/**
- * hole_size - figure out the size of a hole
- * @inode: 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)
+typedef const __be64 *(*gfs2_metadata_walker)(
+		struct metapath *mp,
+		const __be64 *start, const __be64 *end,
+		u64 factor, void *data);
+
+#define WALK_STOP ((__be64 *)0)
+#define WALK_NEXT ((__be64 *)1)
+
+static int gfs2_walk_metadata(struct inode *inode, sector_t lblock,
+		u64 len, struct metapath *mp, gfs2_metadata_walker walker,
+		void *data)
 {
+	struct metapath clone;
 	struct gfs2_inode *ip = GFS2_I(inode);
 	struct gfs2_sbd *sdp = GFS2_SB(inode);
-	struct metapath mp_eof;
+	const __be64 *start, *end, *ptr;
 	u64 factor = 1;
-	int hgt;
-	u64 holesz = 0;
-	const __be64 *first, *end, *ptr;
-	const struct buffer_head *bh;
-	u64 lblock_stop = (i_size_read(inode) - 1) >> inode->i_blkbits;
-	int zeroptrs;
-	bool done = false;
-
-	/* Get another metapath, to the very last byte */
-	find_metapath(sdp, lblock_stop, &mp_eof, ip->i_height);
-	for (hgt = ip->i_height - 1; 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;
-		}
-		if (factor * zeroptrs >= lblock_stop - lblock + 1) {
-			holesz = lblock_stop - lblock + 1;
+	unsigned int hgt;
+	int ret = 0;
+
+	for (hgt = ip->i_height - 1; hgt >= mp->mp_aheight; hgt--)
+		factor *= sdp->sd_inptrs;
+
+	for (;;) {
+		u64 step;
+
+		/* Walk indirect block. */
+		start = metapointer(hgt, mp);
+		end = metaend(hgt, mp);
+
+		step = (end - start) * factor;
+		if (step > len)
+			end = start + DIV_ROUND_UP(len, factor);
+
+		ptr = walker(mp, start, end, factor, data);
+		if (ptr == WALK_STOP)
+			break;
+		if (step >= len)
 			break;
+		len -= step;
+		if (ptr != WALK_NEXT) {
+			BUG_ON(!*ptr);
+			mp->mp_list[hgt] += ptr - start;
+			goto fill_up_metapath;
 		}
-		holesz += factor * zeroptrs;
 
+lower_metapath:
+		/* Decrease height of metapath. */
+		if (mp != &clone) {
+			clone_metapath(&clone, mp);
+			mp = &clone;
+		}
+		brelse(mp->mp_bh[hgt]);
+		mp->mp_bh[hgt] = NULL;
+		if (!hgt)
+			break;
+		hgt--;
 		factor *= sdp->sd_inptrs;
-		if (hgt && (mp->mp_list[hgt - 1] < mp_eof.mp_list[hgt - 1]))
-			(mp->mp_list[hgt - 1])++;
+
+		/* Advance in metadata tree. */
+		(mp->mp_list[hgt])++;
+		start = metapointer(hgt, mp);
+		end = metaend(hgt, mp);
+		if (start >= end) {
+			mp->mp_list[hgt] = 0;
+			if (!hgt)
+				break;
+			goto lower_metapath;
+		}
+
+fill_up_metapath:
+		/* Increase height of metapath. */
+		if (mp != &clone) {
+			clone_metapath(&clone, mp);
+			mp = &clone;
+		}
+		ret = fillup_metapath(ip, mp, ip->i_height - 1);
+		if (ret < 0)
+			break;
+		hgt += ret;
+		for (; ret; ret--)
+			do_div(factor, sdp->sd_inptrs);
+		mp->mp_aheight = hgt + 1;
+	}
+	if (mp == &clone)
+		release_metapath(mp);
+	return ret;
+}
+
+struct gfs2_hole_walker_args {
+	u64 blocks;
+};
+
+static const __be64 *gfs2_hole_walker(struct metapath *mp,
+		const __be64 *start, const __be64 *end,
+		u64 factor, void *data)
+{
+	struct gfs2_hole_walker_args *args = data;
+	const __be64 *ptr;
+
+	for (ptr = start; ptr < end; ptr++) {
+		if (*ptr) {
+			args->blocks += (ptr - start) * factor;
+			if (mp->mp_aheight == mp->mp_fheight)
+				return WALK_STOP;
+			return ptr;  /* increase height */
+		}
 	}
-	return holesz << inode->i_blkbits;
+	args->blocks += (end - start) * factor;
+	return WALK_NEXT;
+}
+
+/**
+ * gfs2_hole_size - figure out the size of a hole
+ * @inode: The inode
+ * @lblock: The logical starting block number
+ * @len: How far to look (in blocks)
+ * @mp: The metapath at lblock
+ * @iomap: The iomap to store the hole size in
+ *
+ * This function modifies @mp.
+ *
+ * Returns: errno on error
+ */
+static int gfs2_hole_size(struct inode *inode, sector_t lblock, u64 len,
+			  struct metapath *mp, struct iomap *iomap)
+{
+	struct gfs2_hole_walker_args args = { };
+	int ret = 0;
+
+	ret = gfs2_walk_metadata(inode, lblock, len, mp, gfs2_hole_walker, &args);
+	if (!ret)
+		iomap->length = args.blocks << inode->i_blkbits;
+	return ret;
 }
 
 static void gfs2_stuffed_iomap(struct inode *inode, struct iomap *iomap)
@@ -780,7 +875,7 @@ int gfs2_iomap_begin(struct inode *inode, loff_t pos, loff_t length,
 		if (pos >= size)
 			ret = -ENOENT;
 		else if (height <= ip->i_height)
-			iomap->length = hole_size(inode, lblock, &mp);
+			ret = gfs2_hole_size(inode, lblock, len, &mp, iomap);
 		else
 			iomap->length = size - pos;
 	}
-- 
2.17.0

  parent reply	other threads:[~2018-05-14 15:36 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-14 15:36 [PATCH v4 00/11] gfs2 iomap write support Andreas Gruenbacher
2018-05-14 15:36 ` [PATCH v4 01/11] gfs2: Update find_metapath comment Andreas Gruenbacher
2018-05-14 15:36 ` Andreas Gruenbacher [this message]
2018-05-14 15:36 ` [PATCH v4 03/11] gfs2: gfs2_stuffed_write_end cleanup Andreas Gruenbacher
2018-05-14 15:36 ` [PATCH v4 04/11] gfs2: Remove ordered write mode handling from gfs2_trans_add_data Andreas Gruenbacher
2018-05-14 15:36 ` [PATCH v4 05/11] gfs2: Iomap cleanups and improvements Andreas Gruenbacher
2018-05-14 15:36 ` [PATCH v4 06/11] iomap: Add write_{begin,end} iomap operations Andreas Gruenbacher
2018-05-15  1:11   ` Dave Chinner
2018-05-15  7:22     ` Christoph Hellwig
2018-05-15  8:16       ` Andreas Gruenbacher
2018-05-18 16:04         ` Christoph Hellwig
2018-05-25 17:58           ` Andreas Grünbacher
2018-05-28 13:02             ` Christoph Hellwig
2018-05-14 15:36 ` [PATCH v4 07/11] gfs2: iomap buffered write support Andreas Gruenbacher
2018-05-14 15:36 ` [PATCH v4 08/11] gfs2: gfs2_extent_length cleanup Andreas Gruenbacher
2018-05-14 15:36 ` [PATCH v4 09/11] gfs2: iomap direct I/O support Andreas Gruenbacher
2018-05-15  7:31   ` Christoph Hellwig
2018-05-16 20:36     ` Andreas Gruenbacher
2018-05-14 15:36 ` [PATCH v4 10/11] gfs2: Remove gfs2_write_{begin,end} Andreas Gruenbacher
2018-05-14 15:36 ` [PATCH v4 11/11] iomap: Complete partial direct I/O writes synchronously Andreas Gruenbacher
2018-05-15  7:24   ` Christoph Hellwig
2018-05-16 20:27     ` Andreas Gruenbacher
2018-05-18 15:56       ` Christoph Hellwig
2018-05-18 18:35         ` Andreas Grünbacher

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