[PATCH 3/3] xfs: rewrite getbmap using the xfs_iext_* helpers

From: Christoph Hellwig <hch@lst.de>
To: linux-xfs@vger.kernel.org
Subject: [PATCH 3/3] xfs: rewrite getbmap using the xfs_iext_* helpers
Date: Mon, 28 Aug 2017 09:28:28 +0200	[thread overview]
Message-ID: <20170828072828.23354-4-hch@lst.de> (raw)
In-Reply-To: <20170828072828.23354-1-hch@lst.de>

By not indirecting through xfs_bmapi_read we can simply xfs_getbmap a
lot.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 fs/xfs/xfs_bmap_util.c | 492 ++++++++++++++++++-------------------------------
 1 file changed, 177 insertions(+), 315 deletions(-)

diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c
index 9e3cc2146d5b..cb980e072f15 100644
--- a/fs/xfs/xfs_bmap_util.c
+++ b/fs/xfs/xfs_bmap_util.c
@@ -379,125 +379,68 @@ xfs_bmap_count_blocks(
 	return 0;
 }
 
-/*
- * returns 1 for success, 0 if we failed to map the extent.
- */
-STATIC int
-xfs_getbmapx_fix_eof_hole(
-	xfs_inode_t		*ip,		/* xfs incore inode pointer */
-	int			whichfork,
-	struct getbmapx		*out,		/* output structure */
-	int			prealloced,	/* this is a file with
-						 * preallocated data space */
-	__int64_t		end,		/* last block requested */
-	xfs_fsblock_t		startblock,
-	bool			moretocome)
+static void
+xfs_getbmap_report_one(
+	struct xfs_inode		*ip,
+	struct getbmapx			*bmv,
+	int64_t				bmv_end,
+	struct xfs_bmbt_irec		*got,
+	struct getbmapx			*p)
 {
-	__int64_t		fixlen;
-	xfs_mount_t		*mp;		/* file system mount point */
-	xfs_ifork_t		*ifp;		/* inode fork pointer */
-	xfs_extnum_t		lastx;		/* last extent pointer */
-	xfs_fileoff_t		fileblock;
-
-	if (startblock == HOLESTARTBLOCK) {
-		mp = ip->i_mount;
-		out->bmv_block = -1;
-		fixlen = XFS_FSB_TO_BB(mp, XFS_B_TO_FSB(mp, XFS_ISIZE(ip)));
-		fixlen -= out->bmv_offset;
-		if (prealloced && out->bmv_offset + out->bmv_length == end) {
-			/* Came to hole at EOF. Trim it. */
-			if (fixlen <= 0)
-				return 0;
-			out->bmv_length = fixlen;
-		}
+	if (isnullstartblock(got->br_startblock) ||
+	    got->br_startblock == DELAYSTARTBLOCK) {
+		/*
+		 * Delalloc extents that start beyond EOF can occur due to
+		 * speculative EOF allocation when the delalloc extent is larger
+		 * than the largest freespace extent at conversion time.  These
+		 * extents cannot be converted by data writeback, so can exist
+		 * here even if we are not supposed to be finding delalloc
+		 * extents.
+		 */
+		if (got->br_startoff < XFS_B_TO_FSB(ip->i_mount, XFS_ISIZE(ip)))
+			ASSERT((bmv->bmv_iflags & BMV_IF_DELALLOC) != 0);
+
+		p->bmv_oflags |= BMV_OF_DELALLOC;
+		p->bmv_block = -2;
 	} else {
-		if (startblock == DELAYSTARTBLOCK)
-			out->bmv_block = -2;
-		else
-			out->bmv_block = xfs_fsb_to_db(ip, startblock);
-		fileblock = XFS_BB_TO_FSB(ip->i_mount, out->bmv_offset);
-		ifp = XFS_IFORK_PTR(ip, whichfork);
-		if (!moretocome &&
-		    xfs_iext_bno_to_ext(ifp, fileblock, &lastx) &&
-		   (lastx == xfs_iext_count(ifp) - 1))
-			out->bmv_oflags |= BMV_OF_LAST;
+		p->bmv_block = xfs_fsb_to_db(ip, got->br_startblock);
 	}
 
-	return 1;
+	if (got->br_state == XFS_EXT_UNWRITTEN)
+		p->bmv_oflags |= BMV_OF_PREALLOC;
+
+	p->bmv_offset = XFS_FSB_TO_BB(ip->i_mount, got->br_startoff);
+	p->bmv_length = XFS_FSB_TO_BB(ip->i_mount, got->br_blockcount);
+
+	bmv->bmv_offset = p->bmv_offset + p->bmv_length;
+	bmv->bmv_length = max_t(__int64_t, 0, bmv_end - bmv->bmv_offset);
+	bmv->bmv_entries++;
 }
 
-/* Adjust the reported bmap around shared/unshared extent transitions. */
-STATIC int
-xfs_getbmap_adjust_shared(
+static void
+xfs_getbmap_report_hole(
 	struct xfs_inode		*ip,
-	int				whichfork,
-	struct xfs_bmbt_irec		*map,
-	struct getbmapx			*out,
-	struct xfs_bmbt_irec		*next_map)
+	struct getbmapx			*bmv,
+	int64_t				bmv_end,
+	xfs_fileoff_t			bno,
+	xfs_fileoff_t			end,
+	struct getbmapx			*p)
 {
-	struct xfs_mount		*mp = ip->i_mount;
-	xfs_agnumber_t			agno;
-	xfs_agblock_t			agbno;
-	xfs_agblock_t			ebno;
-	xfs_extlen_t			elen;
-	xfs_extlen_t			nlen;
-	int				error;
+	if (bmv->bmv_iflags & BMV_IF_NO_HOLES)
+		return;
 
-	next_map->br_startblock = NULLFSBLOCK;
-	next_map->br_startoff = NULLFILEOFF;
-	next_map->br_blockcount = 0;
+	p->bmv_block = -1;
+	p->bmv_offset = XFS_FSB_TO_BB(ip->i_mount, bno);
+	p->bmv_length = XFS_FSB_TO_BB(ip->i_mount, end - bno);
 
-	/* Only written data blocks can be shared. */
-	if (!xfs_is_reflink_inode(ip) ||
-	    whichfork != XFS_DATA_FORK ||
-	    !xfs_bmap_is_real_extent(map))
-		return 0;
-
-	agno = XFS_FSB_TO_AGNO(mp, map->br_startblock);
-	agbno = XFS_FSB_TO_AGBNO(mp, map->br_startblock);
-	error = xfs_reflink_find_shared(mp, agno, agbno, map->br_blockcount,
-			&ebno, &elen, true);
-	if (error)
-		return error;
-
-	if (ebno == NULLAGBLOCK) {
-		/* No shared blocks at all. */
-		return 0;
-	} else if (agbno == ebno) {
-		/*
-		 * Shared extent at (agbno, elen).  Shrink the reported
-		 * extent length and prepare to move the start of map[i]
-		 * to agbno+elen, with the aim of (re)formatting the new
-		 * map[i] the next time through the inner loop.
-		 */
-		out->bmv_length = XFS_FSB_TO_BB(mp, elen);
-		out->bmv_oflags |= BMV_OF_SHARED;
-		if (elen != map->br_blockcount) {
-			*next_map = *map;
-			next_map->br_startblock += elen;
-			next_map->br_startoff += elen;
-			next_map->br_blockcount -= elen;
-		}
-		map->br_blockcount -= elen;
-	} else {
-		/*
-		 * There's an unshared extent (agbno, ebno - agbno)
-		 * followed by shared extent at (ebno, elen).  Shrink
-		 * the reported extent length to cover only the unshared
-		 * extent and prepare to move up the start of map[i] to
-		 * ebno, with the aim of (re)formatting the new map[i]
-		 * the next time through the inner loop.
-		 */
-		*next_map = *map;
-		nlen = ebno - agbno;
-		out->bmv_length = XFS_FSB_TO_BB(mp, nlen);
-		next_map->br_startblock += nlen;
-		next_map->br_startoff += nlen;
-		next_map->br_blockcount -= nlen;
-		map->br_blockcount -= nlen;
-	}
+	bmv->bmv_offset = p->bmv_offset + p->bmv_length;
+	bmv->bmv_length = max_t(__int64_t, 0, bmv_end - bmv->bmv_offset);
+	bmv->bmv_entries++;
+}
 
-	return 0;
+static inline bool xfs_getbmap_full(struct getbmapx *bmv, int nr_entries)
+{
+	return bmv->bmv_length == 0 || nr_entries >= bmv->bmv_count - 1;
 }
 
 /*
@@ -514,119 +457,72 @@ xfs_getbmap(
 	xfs_bmap_format_t	formatter,	/* format to user */
 	void			*arg)		/* formatter arg */
 {
-	__int64_t		bmvend;		/* last block requested */
-	int			error = 0;	/* return value */
-	__int64_t		fixlen;		/* length for -1 case */
-	int			i;		/* extent number */
-	int			lock;		/* lock state */
-	xfs_bmbt_irec_t		*map;		/* buffer for user's data */
-	xfs_mount_t		*mp;		/* file system mount point */
-	int			nex;		/* # of user extents can do */
-	int			subnex;		/* # of bmapi's can do */
-	int			nmap;		/* number of map entries */
-	struct getbmapx		*out;		/* output structure */
-	int			whichfork;	/* data or attr fork */
-	int			prealloced;	/* this is a file with
-						 * preallocated data space */
-	int			iflags;		/* interface flags */
-	int			bmapi_flags;	/* flags for xfs_bmapi */
-	int			cur_ext = 0;
-	struct xfs_bmbt_irec	inject_map;
-
-	mp = ip->i_mount;
-	iflags = bmv->bmv_iflags;
+	struct xfs_mount	*mp = ip->i_mount;
+	int			iflags = bmv->bmv_iflags;
+	int			whichfork, lock, i, nr_entries = 0, error = 0;
+	__int64_t		bmv_end, max_len;
+	xfs_fileoff_t		bno, first_bno;
+	struct xfs_ifork	*ifp;
+	struct getbmapx		*out;
+	struct xfs_bmbt_irec	got, rec;
+	xfs_filblks_t		len;
+	xfs_extnum_t		idx;
 
 #ifndef DEBUG
 	/* Only allow CoW fork queries if we're debugging. */
 	if (iflags & BMV_IF_COWFORK)
 		return -EINVAL;
 #endif
+
 	if ((iflags & BMV_IF_ATTRFORK) && (iflags & BMV_IF_COWFORK))
 		return -EINVAL;
 
+	if (bmv->bmv_count <= 1)
+		return -EINVAL;
+	if (bmv->bmv_count > ULONG_MAX / sizeof(struct getbmapx))
+		return -ENOMEM;
+
+	if (bmv->bmv_length < -1)
+		return -EINVAL;
+
+	bmv->bmv_entries = 0;
+	if (bmv->bmv_length == 0)
+		return 0;
+
+	out = kmem_zalloc_large(bmv->bmv_count * sizeof(struct getbmapx), 0);
+	if (!out)
+		return -ENOMEM;
+
 	if (iflags & BMV_IF_ATTRFORK)
 		whichfork = XFS_ATTR_FORK;
 	else if (iflags & BMV_IF_COWFORK)
 		whichfork = XFS_COW_FORK;
 	else
 		whichfork = XFS_DATA_FORK;
+	ifp = XFS_IFORK_PTR(ip, whichfork);
 
+	xfs_ilock(ip, XFS_IOLOCK_SHARED);
 	switch (whichfork) {
 	case XFS_ATTR_FORK:
-		if (XFS_IFORK_Q(ip)) {
-			if (ip->i_d.di_aformat != XFS_DINODE_FMT_EXTENTS &&
-			    ip->i_d.di_aformat != XFS_DINODE_FMT_BTREE &&
-			    ip->i_d.di_aformat != XFS_DINODE_FMT_LOCAL)
-				return -EINVAL;
-		} else if (unlikely(
-			   ip->i_d.di_aformat != 0 &&
-			   ip->i_d.di_aformat != XFS_DINODE_FMT_EXTENTS)) {
-			XFS_ERROR_REPORT("xfs_getbmap", XFS_ERRLEVEL_LOW,
-					 ip->i_mount);
-			return -EFSCORRUPTED;
-		}
+		if (!XFS_IFORK_Q(ip))
+			goto out_unlock_iolock;
 
-		prealloced = 0;
-		fixlen = 1LL << 32;
+		max_len = 1LL << 32;
+		lock = xfs_ilock_attr_map_shared(ip);
 		break;
 	case XFS_COW_FORK:
-		if (ip->i_cformat != XFS_DINODE_FMT_EXTENTS)
-			return -EINVAL;
+		/* No CoW fork? Just return */
+		if (!ifp)
+			goto out_unlock_iolock;
 
-		if (xfs_get_cowextsz_hint(ip)) {
-			prealloced = 1;
-			fixlen = mp->m_super->s_maxbytes;
-		} else {
-			prealloced = 0;
-			fixlen = XFS_ISIZE(ip);
-		}
-		break;
-	default:
-		/* Local format data forks report no extents. */
-		if (ip->i_d.di_format == XFS_DINODE_FMT_LOCAL) {
-			bmv->bmv_entries = 0;
-			return 0;
-		}
-		if (ip->i_d.di_format != XFS_DINODE_FMT_EXTENTS &&
-		    ip->i_d.di_format != XFS_DINODE_FMT_BTREE)
-			return -EINVAL;
+		if (xfs_get_cowextsz_hint(ip))
+			max_len = mp->m_super->s_maxbytes;
+		else
+			max_len = XFS_ISIZE(ip);
 
-		if (xfs_get_extsz_hint(ip) ||
-		    ip->i_d.di_flags & (XFS_DIFLAG_PREALLOC|XFS_DIFLAG_APPEND)){
-			prealloced = 1;
-			fixlen = mp->m_super->s_maxbytes;
-		} else {
-			prealloced = 0;
-			fixlen = XFS_ISIZE(ip);
-		}
+		lock = XFS_ILOCK_SHARED;
+		xfs_ilock(ip, lock);
 		break;
-	}
-
-	if (bmv->bmv_length == -1) {
-		fixlen = XFS_FSB_TO_BB(mp, XFS_B_TO_FSB(mp, fixlen));
-		bmv->bmv_length =
-			max_t(__int64_t, fixlen - bmv->bmv_offset, 0);
-	} else if (bmv->bmv_length == 0) {
-		bmv->bmv_entries = 0;
-		return 0;
-	} else if (bmv->bmv_length < 0) {
-		return -EINVAL;
-	}
-
-	nex = bmv->bmv_count - 1;
-	if (nex <= 0)
-		return -EINVAL;
-	bmvend = bmv->bmv_offset + bmv->bmv_length;
-
-
-	if (bmv->bmv_count > ULONG_MAX / sizeof(struct getbmapx))
-		return -ENOMEM;
-	out = kmem_zalloc_large(bmv->bmv_count * sizeof(struct getbmapx), 0);
-	if (!out)
-		return -ENOMEM;
-
-	xfs_ilock(ip, XFS_IOLOCK_SHARED);
-	switch (whichfork) {
 	case XFS_DATA_FORK:
 		if (!(iflags & BMV_IF_DELALLOC) &&
 		    (ip->i_delayed_blks || XFS_ISIZE(ip) > ip->i_d.di_size)) {
@@ -644,147 +540,113 @@ xfs_getbmap(
 			 */
 		}
 
+		if (xfs_get_extsz_hint(ip) ||
+		    (ip->i_d.di_flags &
+		     (XFS_DIFLAG_PREALLOC | XFS_DIFLAG_APPEND)))
+			max_len = mp->m_super->s_maxbytes;
+		else
+			max_len = XFS_ISIZE(ip);
+
 		lock = xfs_ilock_data_map_shared(ip);
 		break;
-	case XFS_COW_FORK:
-		lock = XFS_ILOCK_SHARED;
-		xfs_ilock(ip, lock);
-		break;
-	case XFS_ATTR_FORK:
-		lock = xfs_ilock_attr_map_shared(ip);
+	}
+
+	switch (XFS_IFORK_FORMAT(ip, whichfork)) {
+	case XFS_DINODE_FMT_EXTENTS:
+	case XFS_DINODE_FMT_BTREE:
 		break;
+	case XFS_DINODE_FMT_LOCAL:
+		/* Local format inode forks report no extents. */
+		goto out_unlock_ilock;
+	default:
+		error = -EINVAL;
+		goto out_unlock_ilock;
 	}
 
-	/*
-	 * Don't let nex be bigger than the number of extents
-	 * we can have assuming alternating holes and real extents.
-	 */
-	if (nex > XFS_IFORK_NEXTENTS(ip, whichfork) * 2 + 1)
-		nex = XFS_IFORK_NEXTENTS(ip, whichfork) * 2 + 1;
+	if (bmv->bmv_length == -1) {
+		max_len = XFS_FSB_TO_BB(mp, XFS_B_TO_FSB(mp, max_len));
+		bmv->bmv_length = max(0LL, max_len - bmv->bmv_offset);
+	}
 
-	bmapi_flags = xfs_bmapi_aflag(whichfork);
-	if (!(iflags & BMV_IF_PREALLOC))
-		bmapi_flags |= XFS_BMAPI_IGSTATE;
+	bmv_end = bmv->bmv_offset + bmv->bmv_length;
 
-	/*
-	 * Allocate enough space to handle "subnex" maps at a time.
-	 */
-	error = -ENOMEM;
-	subnex = 16;
-	map = kmem_alloc(subnex * sizeof(*map), KM_MAYFAIL | KM_NOFS);
-	if (!map)
+	first_bno = bno = XFS_BB_TO_FSBT(mp, bmv->bmv_offset);
+	len = XFS_BB_TO_FSB(mp, bmv->bmv_length);
+
+	if (!(ifp->if_flags & XFS_IFEXTENTS)) {
+		error = xfs_iread_extents(NULL, ip, whichfork);
+		if (error)
+			goto out_unlock_ilock;
+	}
+
+	if (!xfs_iext_lookup_extent(ip, ifp, bno, &idx, &got))
 		goto out_unlock_ilock;
 
-	bmv->bmv_entries = 0;
+	while (!xfs_getbmap_full(bmv, nr_entries)) {
+		struct getbmapx		*p = &out[nr_entries];
 
-	if (XFS_IFORK_NEXTENTS(ip, whichfork) == 0 &&
-	    (whichfork == XFS_ATTR_FORK || !(iflags & BMV_IF_DELALLOC))) {
-		error = 0;
-		goto out_free_map;
-	}
+		xfs_trim_extent(&got, first_bno, len);
 
-	do {
-		nmap = (nex> subnex) ? subnex : nex;
-		error = xfs_bmapi_read(ip, XFS_BB_TO_FSBT(mp, bmv->bmv_offset),
-				       XFS_BB_TO_FSB(mp, bmv->bmv_length),
-				       map, &nmap, bmapi_flags);
-		if (error)
-			goto out_free_map;
-		ASSERT(nmap <= subnex);
-
-		for (i = 0; i < nmap && bmv->bmv_length &&
-				cur_ext < bmv->bmv_count - 1; i++) {
-			out[cur_ext].bmv_oflags = 0;
-			if (map[i].br_state == XFS_EXT_UNWRITTEN)
-				out[cur_ext].bmv_oflags |= BMV_OF_PREALLOC;
-			else if (map[i].br_startblock == DELAYSTARTBLOCK)
-				out[cur_ext].bmv_oflags |= BMV_OF_DELALLOC;
-			out[cur_ext].bmv_offset =
-				XFS_FSB_TO_BB(mp, map[i].br_startoff);
-			out[cur_ext].bmv_length =
-				XFS_FSB_TO_BB(mp, map[i].br_blockcount);
-			out[cur_ext].bmv_unused1 = 0;
-			out[cur_ext].bmv_unused2 = 0;
+		/*
+		 * Report an entry for a hole if this extent doesn't directly
+		 * follow the previous one.
+		 */
+		if (got.br_startoff > bno) {
+			xfs_getbmap_report_hole(ip, bmv, bmv_end, bno,
+					got.br_startoff, p);
+			if (xfs_getbmap_full(bmv, ++nr_entries))
+				break;
+			p = &out[nr_entries];
+		}
 
-			/*
-			 * delayed allocation extents that start beyond EOF can
-			 * occur due to speculative EOF allocation when the
-			 * delalloc extent is larger than the largest freespace
-			 * extent at conversion time. These extents cannot be
-			 * converted by data writeback, so can exist here even
-			 * if we are not supposed to be finding delalloc
-			 * extents.
-			 */
-			if (map[i].br_startblock == DELAYSTARTBLOCK &&
-			    map[i].br_startoff < XFS_B_TO_FSB(mp, XFS_ISIZE(ip)))
-				ASSERT((iflags & BMV_IF_DELALLOC) != 0);
-
-                        if (map[i].br_startblock == HOLESTARTBLOCK &&
-			    whichfork == XFS_ATTR_FORK) {
-				/* came to the end of attribute fork */
-				out[cur_ext].bmv_oflags |= BMV_OF_LAST;
-				goto out_free_map;
-			}
+		/*
+		 * In order to report shared extents accurately, we report each
+		 * distinct shared / unshared part of a single bmbt record with
+		 * an individual getbmapx record.
+		 */
+		rec = got;
+		for (;;) {
+			bool			shared = false, trimmed = false;
+			xfs_fileoff_t		len;
 
-			/* Is this a shared block? */
-			error = xfs_getbmap_adjust_shared(ip, whichfork,
-					&map[i], &out[cur_ext], &inject_map);
+			error = xfs_reflink_trim_around_shared(ip, &rec,
+					&shared, &trimmed);
 			if (error)
-				goto out_free_map;
+				goto out_unlock_ilock;
 
-			if (!xfs_getbmapx_fix_eof_hole(ip, whichfork,
-					&out[cur_ext], prealloced, bmvend,
-					map[i].br_startblock,
-					inject_map.br_startblock != NULLFSBLOCK))
-				goto out_free_map;
+			xfs_getbmap_report_one(ip, bmv, bmv_end, &rec, p);
+			if (shared)
+				p->bmv_oflags |= BMV_OF_SHARED;
+			if (!trimmed)
+				break;
 
-			bmv->bmv_offset =
-				out[cur_ext].bmv_offset +
-				out[cur_ext].bmv_length;
-			bmv->bmv_length =
-				max_t(__int64_t, 0, bmvend - bmv->bmv_offset);
+			len = got.br_startoff + got.br_blockcount -
+				(rec.br_startoff + rec.br_blockcount);
 
-			/*
-			 * In case we don't want to return the hole,
-			 * don't increase cur_ext so that we can reuse
-			 * it in the next loop.
-			 */
-			if ((iflags & BMV_IF_NO_HOLES) &&
-			    map[i].br_startblock == HOLESTARTBLOCK) {
-				memset(&out[cur_ext], 0, sizeof(out[cur_ext]));
-				continue;
-			}
+			rec.br_startoff += rec.br_blockcount;
+			if (rec.br_startblock != DELAYSTARTBLOCK)
+				rec.br_startblock += rec.br_blockcount;
+			rec.br_blockcount = len;
+		}
 
-			/*
-			 * In order to report shared extents accurately,
-			 * we report each distinct shared/unshared part
-			 * of a single bmbt record using multiple bmap
-			 * extents.  To make that happen, we iterate the
-			 * same map array item multiple times, each
-			 * time trimming out the subextent that we just
-			 * reported.
-			 *
-			 * Because of this, we must check the out array
-			 * index (cur_ext) directly against bmv_count-1
-			 * to avoid overflows.
-			 */
-			if (inject_map.br_startblock != NULLFSBLOCK) {
-				map[i] = inject_map;
-				i--;
-			}
-			bmv->bmv_entries++;
-			cur_ext++;
+		bno = got.br_startoff + got.br_blockcount;
+		nr_entries++;
+
+		if (!xfs_iext_get_extent(ifp, ++idx, &got)) {
+			p->bmv_oflags |= BMV_OF_LAST;
+			break;
 		}
-	} while (nmap && bmv->bmv_length && cur_ext < bmv->bmv_count - 1);
 
- out_free_map:
-	kmem_free(map);
- out_unlock_ilock:
+		if (bno >= first_bno + len)
+			break;
+	}
+
+out_unlock_ilock:
 	xfs_iunlock(ip, lock);
- out_unlock_iolock:
+out_unlock_iolock:
 	xfs_iunlock(ip, XFS_IOLOCK_SHARED);
 
-	for (i = 0; i < cur_ext; i++) {
+	for (i = 0; i < nr_entries; i++) {
 		/* format results & advance arg */
 		error = formatter(&arg, &out[i]);
 		if (error)
-- 
2.11.0

