Date:	Thu, 22 Jul 2010 10:03:15 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	Renzo Davoli <renzo@...unibo.it>
Cc:	Ext4 Developers List <linux-ext4@...r.kernel.org>,
	Theodore Ts'o <tytso@....edu>
Subject: [PATCH 4/7] libext2fs: Add new function ext2fs_punch()

This function deallocates a range of blocks from a passed-in file.

Signed-off-by: "Theodore Ts'o" <tytso@....edu>
---
 lib/ext2fs/Makefile.in |   32 ++++-
 lib/ext2fs/ext2fs.h    |    6 +
 lib/ext2fs/punch.c     |  324 ++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 356 insertions(+), 6 deletions(-)
 create mode 100644 lib/ext2fs/punch.c

diff --git a/lib/ext2fs/Makefile.in b/lib/ext2fs/Makefile.in
index f25c0b7..763694d 100644
--- a/lib/ext2fs/Makefile.in
+++ b/lib/ext2fs/Makefile.in
@@ -69,6 +69,7 @@ OBJS= $(DEBUGFS_LIB_OBJS) $(RESIZE_LIB_OBJS) $(E2IMAGE_LIB_OBJS) \
 	newdir.o \
 	openfs.o \
 	progress.o \
+	punch.o \
 	read_bb.o \
 	read_bb_file.o \
 	res_gdt.o \
@@ -135,6 +136,8 @@ SRCS= ext2_err.c \
 	$(srcdir)/native.c \
 	$(srcdir)/newdir.c \
 	$(srcdir)/openfs.c \
+	$(srcdir)/progress.c \
+	$(srcdir)/punch.c \
 	$(srcdir)/read_bb.c \
 	$(srcdir)/read_bb_file.c \
 	$(srcdir)/res_gdt.c \
@@ -412,7 +415,7 @@ alloc_tables.o: $(srcdir)/alloc_tables.c $(srcdir)/ext2_fs.h \
  $(top_builddir)/lib/ext2fs/ext2_types.h $(srcdir)/ext2fs.h \
  $(srcdir)/ext2_fs.h $(srcdir)/ext3_extents.h $(top_srcdir)/lib/et/com_err.h \
  $(srcdir)/ext2_io.h $(top_builddir)/lib/ext2fs/ext2_err.h \
- $(srcdir)/ext2_ext_attr.h $(srcdir)/bitops.h
+ $(srcdir)/ext2_ext_attr.h $(srcdir)/bitops.h $(srcdir)/ext2fsP.h
 badblocks.o: $(srcdir)/badblocks.c $(srcdir)/ext2_fs.h \
  $(top_builddir)/lib/ext2fs/ext2_types.h $(srcdir)/ext2fsP.h \
  $(srcdir)/ext2fs.h $(srcdir)/ext2_fs.h $(srcdir)/ext3_extents.h \
@@ -434,7 +437,7 @@ bitmaps.o: $(srcdir)/bitmaps.c $(srcdir)/ext2_fs.h \
  $(top_builddir)/lib/ext2fs/ext2_types.h $(srcdir)/ext2fs.h \
  $(srcdir)/ext2_fs.h $(srcdir)/ext3_extents.h $(top_srcdir)/lib/et/com_err.h \
  $(srcdir)/ext2_io.h $(top_builddir)/lib/ext2fs/ext2_err.h \
- $(srcdir)/ext2_ext_attr.h $(srcdir)/bitops.h
+ $(srcdir)/ext2_ext_attr.h $(srcdir)/bitops.h $(srcdir)/ext2fsP.h
 bitops.o: $(srcdir)/bitops.c $(srcdir)/ext2_fs.h \
  $(top_builddir)/lib/ext2fs/ext2_types.h $(srcdir)/ext2fs.h \
  $(srcdir)/ext2_fs.h $(srcdir)/ext3_extents.h $(top_srcdir)/lib/et/com_err.h \
@@ -541,10 +544,17 @@ freefs.o: $(srcdir)/freefs.c $(srcdir)/ext2_fs.h \
  $(top_builddir)/lib/ext2fs/ext2_err.h $(srcdir)/ext2_ext_attr.h \
  $(srcdir)/bitops.h
 gen_bitmap.o: $(srcdir)/gen_bitmap.c $(srcdir)/ext2_fs.h \
- $(top_builddir)/lib/ext2fs/ext2_types.h $(srcdir)/ext2fs.h \
- $(srcdir)/ext2_fs.h $(srcdir)/ext3_extents.h $(top_srcdir)/lib/et/com_err.h \
- $(srcdir)/ext2_io.h $(top_builddir)/lib/ext2fs/ext2_err.h \
- $(srcdir)/ext2_ext_attr.h $(srcdir)/bitops.h
+ $(top_builddir)/lib/ext2fs/ext2_types.h $(srcdir)/ext2fsP.h \
+ $(srcdir)/ext2fs.h $(srcdir)/ext2_fs.h $(srcdir)/ext3_extents.h \
+ $(top_srcdir)/lib/et/com_err.h $(srcdir)/ext2_io.h \
+ $(top_builddir)/lib/ext2fs/ext2_err.h $(srcdir)/ext2_ext_attr.h \
+ $(srcdir)/bitops.h
+gen_bitmap64.o: $(srcdir)/gen_bitmap64.c $(srcdir)/ext2_fs.h \
+ $(top_builddir)/lib/ext2fs/ext2_types.h $(srcdir)/ext2fsP.h \
+ $(srcdir)/ext2fs.h $(srcdir)/ext2_fs.h $(srcdir)/ext3_extents.h \
+ $(top_srcdir)/lib/et/com_err.h $(srcdir)/ext2_io.h \
+ $(top_builddir)/lib/ext2fs/ext2_err.h $(srcdir)/ext2_ext_attr.h \
+ $(srcdir)/bitops.h $(srcdir)/bmap64.h
 get_pathname.o: $(srcdir)/get_pathname.c $(srcdir)/ext2_fs.h \
  $(top_builddir)/lib/ext2fs/ext2_types.h $(srcdir)/ext2fs.h \
  $(srcdir)/ext2_fs.h $(srcdir)/ext3_extents.h $(top_srcdir)/lib/et/com_err.h \
@@ -655,6 +665,16 @@ openfs.o: $(srcdir)/openfs.c $(srcdir)/ext2_fs.h \
  $(srcdir)/ext2_fs.h $(srcdir)/ext3_extents.h $(top_srcdir)/lib/et/com_err.h \
  $(srcdir)/ext2_io.h $(top_builddir)/lib/ext2fs/ext2_err.h \
  $(srcdir)/ext2_ext_attr.h $(srcdir)/bitops.h $(srcdir)/e2image.h
+progress.o: $(srcdir)/progress.c $(srcdir)/ext2fs.h \
+ $(top_builddir)/lib/ext2fs/ext2_types.h $(srcdir)/ext2_fs.h \
+ $(srcdir)/ext3_extents.h $(top_srcdir)/lib/et/com_err.h $(srcdir)/ext2_io.h \
+ $(top_builddir)/lib/ext2fs/ext2_err.h $(srcdir)/ext2_ext_attr.h \
+ $(srcdir)/bitops.h $(srcdir)/ext2fsP.h
+punch.o: $(srcdir)/punch.c $(srcdir)/ext2_fs.h \
+ $(top_builddir)/lib/ext2fs/ext2_types.h $(srcdir)/ext2fs.h \
+ $(srcdir)/ext2_fs.h $(srcdir)/ext3_extents.h $(top_srcdir)/lib/et/com_err.h \
+ $(srcdir)/ext2_io.h $(top_builddir)/lib/ext2fs/ext2_err.h \
+ $(srcdir)/ext2_ext_attr.h $(srcdir)/bitops.h
 read_bb.o: $(srcdir)/read_bb.c $(srcdir)/ext2_fs.h \
  $(top_builddir)/lib/ext2fs/ext2_types.h $(srcdir)/ext2fs.h \
  $(srcdir)/ext2_fs.h $(srcdir)/ext3_extents.h $(top_srcdir)/lib/et/com_err.h \
diff --git a/lib/ext2fs/ext2fs.h b/lib/ext2fs/ext2fs.h
index e2c3b09..f3531c0 100644
--- a/lib/ext2fs/ext2fs.h
+++ b/lib/ext2fs/ext2fs.h
@@ -1209,6 +1209,12 @@ extern errcode_t ext2fs_check_if_mounted(const char *file, int *mount_flags);
 extern errcode_t ext2fs_check_mount_point(const char *device, int *mount_flags,
 					  char *mtpt, int mtlen);
 
+/* punch.c */
+extern errcode_t ext2fs_punch(ext2_filsys fs, ext2_ino_t ino,
+			      struct ext2_inode *inode,
+			      char *block_buf, blk64_t start,
+			      blk64_t end);
+
 /* namei.c */
 extern errcode_t ext2fs_lookup(ext2_filsys fs, ext2_ino_t dir, const char *name,
 			 int namelen, char *buf, ext2_ino_t *inode);
diff --git a/lib/ext2fs/punch.c b/lib/ext2fs/punch.c
new file mode 100644
index 0000000..8c6ec54
--- /dev/null
+++ b/lib/ext2fs/punch.c
@@ -0,0 +1,324 @@
+/*
+ * punch.c --- deallocate blocks allocated to an inode
+ *
+ * Copyright (C) 2010 Theodore Ts'o.
+ *
+ * %Begin-Header%
+ * This file may be redistributed under the terms of the GNU Library
+ * General Public License, version 2.
+ * %End-Header%
+ */
+
+#include <stdio.h>
+#include <string.h>
+#if HAVE_UNISTD_H
+#include <unistd.h>
+#endif
+#include <errno.h>
+
+#include "ext2_fs.h"
+#include "ext2fs.h"
+
+#undef PUNCH_DEBUG
+
+/*
+ * This function returns 1 if the specified block is all zeros
+ */
+static int check_zero_block(char *buf, int blocksize)
+{
+	char	*cp = buf;
+	int	left = blocksize;
+
+	while (left > 0) {
+		if (*cp++)
+			return 0;
+		left--;
+	}
+	return 1;
+}
+
+/*
+ * This clever recursive function handles i_blocks[] as well as
+ * indirect, double indirect, and triple indirect blocks.  It iterates
+ * over the entries in the i_blocks array or indirect blocks, and for
+ * each one, will recursively handle any indirect blocks and then
+ * frees and deallocates the blocks.
+ */
+static errcode_t ind_punch(ext2_filsys fs, struct ext2_inode *inode,
+			   char *block_buf, blk_t *p, int level,
+			   blk_t start, blk_t count, int max)
+{
+	errcode_t	retval;
+	blk_t		b, offset;
+	int		i, incr;
+	int		freed = 0;
+
+#ifdef PUNCH_DEBUG
+	printf("Entering ind_punch, level %d, start %u, count %u, "
+	       "max %d\n", level, start, count, max);
+#endif
+	incr = 1 << ((EXT2_BLOCK_SIZE_BITS(fs->super)-2)*level);
+	for (i=0, offset=0; i < max; i++, p++, offset += incr) {
+		if (offset > count)
+			break;
+		if (*p == 0 || (offset+incr) <= start)
+			continue;
+		b = *p;
+		if (level > 0) {
+			blk_t start2;
+#ifdef PUNCH_DEBUG
+			printf("Reading indirect block %u\n", b);
+#endif
+			retval = ext2fs_read_ind_block(fs, b, block_buf);
+			if (retval)
+				return retval;
+			start2 = (start > offset) ? start - offset : 0;
+			retval = ind_punch(fs, inode, block_buf + fs->blocksize,
+					   (blk_t *) block_buf, level - 1,
+					   start2, count - offset,
+					   fs->blocksize >> 2);
+			if (retval)
+				return retval;
+			retval = ext2fs_write_ind_block(fs, b, block_buf);
+			if (retval)
+				return retval;
+			if (!check_zero_block(block_buf, fs->blocksize))
+				continue;
+		}
+#ifdef PUNCH_DEBUG
+		printf("Freeing block %u (offset %d)\n", b, offset);
+#endif
+		ext2fs_block_alloc_stats(fs, b, -1);
+		*p = 0;
+		freed++;
+	}
+#ifdef PUNCH_DEBUG
+	printf("Freed %d blocks\n", freed);
+#endif
+	return ext2fs_iblk_sub_blocks(fs, inode, freed);
+}
+
+static errcode_t ext2fs_punch_ind(ext2_filsys fs, struct ext2_inode *inode,
+				  char *block_buf, blk_t start, blk_t count)
+{
+	errcode_t		retval;
+	char			*buf = 0;
+	int			level;
+	int			num = EXT2_NDIR_BLOCKS;
+	blk_t			*bp = inode->i_block;
+	blk_t			addr_per_block;
+	blk_t			max = EXT2_NDIR_BLOCKS;
+
+	if (!block_buf) {
+		retval = ext2fs_get_array(3, fs->blocksize, &buf);
+		if (retval)
+			return retval;
+		block_buf = buf;
+	}
+
+	addr_per_block = (blk_t) fs->blocksize >> 2;
+
+	for (level=0; level < 4; level++, max *= addr_per_block) {
+#ifdef PUNCH_DEBUG
+		printf("Main loop level %d, start %u count %u "
+		       "max %d num %d\n", level, start, count, max, num);
+#endif
+		if (start < max) {
+			retval = ind_punch(fs, inode, block_buf, bp, level,
+					   start, count, num);
+			if (retval)
+				goto errout;
+			if (count > max)
+				count -= max - start;
+			else
+				break;
+			start = 0;
+		} else
+			start -= max;
+		bp += num;
+		if (level == 0) {
+			num = 1;
+			max = 1;
+		}
+	}
+	retval = 0;
+errout:
+	if (buf)
+		ext2fs_free_mem(&buf);
+	return retval;
+}
+
+#ifdef PUNCH_DEBUG
+
+#define dbg_printf(f, a...)  printf(f, ## a)
+
+static void dbg_print_extent(char *desc, struct ext2fs_extent *extent)
+{
+	if (desc)
+		printf("%s: ", desc);
+	printf("extent: lblk %llu--%llu, len %u, pblk %llu, flags: ",
+	       extent->e_lblk, extent->e_lblk + extent->e_len - 1,
+	       extent->e_len, extent->e_pblk);
+	if (extent->e_flags & EXT2_EXTENT_FLAGS_LEAF)
+		fputs("LEAF ", stdout);
+	if (extent->e_flags & EXT2_EXTENT_FLAGS_UNINIT)
+		fputs("UNINIT ", stdout);
+	if (extent->e_flags & EXT2_EXTENT_FLAGS_SECOND_VISIT)
+		fputs("2ND_VISIT ", stdout);
+	if (!extent->e_flags)
+		fputs("(none)", stdout);
+	fputc('\n', stdout);
+
+}
+#else
+#define dbg_print_extent(desc, ex)	do { } while (0)
+#define dbg_printf(f, a...)		do { } while (0)
+#endif
+
+static errcode_t ext2fs_punch_extent(ext2_filsys fs, ext2_ino_t ino,
+				     struct ext2_inode *inode,
+				     blk64_t start, blk64_t end)
+{
+	ext2_extent_handle_t	handle = 0;
+	struct ext2fs_extent	extent;
+	errcode_t		retval;
+	blk64_t			free_start, next;
+	__u32			free_count, newlen;
+	int			freed = 0;
+
+	retval = ext2fs_extent_open2(fs, ino, inode, &handle);
+	if (retval)
+		return retval;
+	ext2fs_extent_goto(handle, start);
+	retval = ext2fs_extent_get(handle, EXT2_EXTENT_CURRENT, &extent);
+	if (retval)
+		goto errout;
+	while (1) {
+		dbg_print_extent("main loop", &extent);
+		next = extent.e_lblk + extent.e_len;
+		dbg_printf("start %llu, end %llu, next %llu\n",
+			   (unsigned long long) start,
+			   (unsigned long long) end,
+			   (unsigned long long) next);
+		if (start <= extent.e_lblk) {
+			if (end < extent.e_lblk)
+				goto next_extent;
+			dbg_printf("Case #1\n");
+			/* Start of deleted region before extent; 
+			   adjust beginning of extent */
+			free_start = extent.e_pblk;
+			if (next > end)
+				free_count = end - extent.e_lblk + 1;
+			else
+				free_count = extent.e_len;
+			extent.e_len -= free_count;
+			extent.e_lblk += free_count;
+			extent.e_pblk += free_count;
+		} else if (end >= next-1) {
+			if (start >= next)
+				break;
+			/* End of deleted region after extent;
+			   adjust end of extent */
+			dbg_printf("Case #2\n");
+			newlen = start - extent.e_lblk;
+			free_start = extent.e_pblk + newlen;
+			free_count = extent.e_len - newlen;
+			extent.e_len = newlen;
+		} else {
+			struct ext2fs_extent	newex;
+
+			dbg_printf("Case #3\n");
+			/* The hard case; we need to split the extent */
+			newex.e_pblk = extent.e_pblk +
+				(end + 1 - extent.e_lblk);
+			newex.e_lblk = end + 1;
+			newex.e_len = next - end - 1;
+			newex.e_flags = extent.e_flags;
+
+			extent.e_len = start - extent.e_lblk;
+			free_start = extent.e_pblk + extent.e_len;
+			free_count = end - start + 1;
+
+			dbg_print_extent("inserting", &newex);
+			retval = ext2fs_extent_insert(handle,
+					EXT2_EXTENT_INSERT_AFTER, &newex);
+			if (retval)
+				goto errout;
+			/* Now pointing at inserted extent; so go back */
+			retval = ext2fs_extent_get(handle,
+						   EXT2_EXTENT_PREV_LEAF,
+						   &newex);
+			if (retval)
+				goto errout;
+		} 
+		if (extent.e_len) {
+			dbg_print_extent("replacing", &extent);
+			retval = ext2fs_extent_replace(handle, 0, &extent);
+		} else {
+			dbg_printf("deleting current extent\n");
+			retval = ext2fs_extent_delete(handle, 0);
+		}
+		if (retval)
+			goto errout;
+		dbg_printf("Free start %llu, free count = %u\n",
+		       free_start, free_count);
+		while (free_count-- > 0) {
+			ext2fs_block_alloc_stats(fs, free_start++, -1);
+			freed++;
+		}
+	next_extent:
+		retval = ext2fs_extent_get(handle, EXT2_EXTENT_NEXT_LEAF,
+					   &extent);
+		if (retval == EXT2_ET_EXTENT_NO_NEXT)
+			break;
+		if (retval)
+			goto errout;
+	}
+	dbg_printf("Freed %d blocks\n", freed);
+	retval = ext2fs_iblk_sub_blocks(fs, inode, freed);
+errout:
+	ext2fs_extent_free(handle);
+	return retval;
+}
+	
+/*
+ * Deallocate all logical blocks starting at start to end, inclusive.
+ * If end is ~0, then this is effectively truncate.
+ */
+extern errcode_t ext2fs_punch(ext2_filsys fs, ext2_ino_t ino,
+			      struct ext2_inode *inode,
+			      char *block_buf, blk64_t start,
+			      blk64_t end)
+{
+	errcode_t		retval;
+	struct ext2_inode	inode_buf;
+
+	if (start > end)
+		return EINVAL;
+
+	if (start == end)
+		return 0;
+
+	/* Read inode structure if necessary */
+	if (!inode) {
+		retval = ext2fs_read_inode(fs, ino, &inode_buf);
+		if (retval)
+			return retval;
+		inode = &inode_buf;
+	}
+	if (inode->i_flags & EXT4_EXTENTS_FL)
+		retval = ext2fs_punch_extent(fs, ino, inode, start, end);
+	else {
+		blk_t	count;
+
+		if (start > ~0U)
+			return 0;
+		count = ((end - start) < ~0U) ? (end - start) : ~0U;
+		retval = ext2fs_punch_ind(fs, inode, block_buf, 
+					  (blk_t) start, count);
+	}
+	if (retval)
+		return retval;
+
+	return ext2fs_write_inode(fs, ino, inode);
+}
-- 
1.7.0.4

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