[PATCH 06/19] fuse2fs: add extent dump function for debugging

["Darrick J. Wong" <djwong@kernel.org>]

From: Darrick J. Wong <djwong@kernel.org>

Add a function to dump an inode's extent map for debugging purposes.
This helped debug a problem with generic/299 failing on 1k fsblock
filesystems:

--- a/tests/generic/299.out	2025-07-15 14:45:15.030113607 -0700
+++ b/tests/generic/299.out.bad	2025-07-16 19:33:50.889344998 -0700
@@ -3,3 +3,4 @@ QA output created by 299
 Run fio with random aio-dio pattern

 Start fallocate/truncate loop
+fio: io_u error on file /opt/direct_aio.0.0: Input/output error: write offset=2602827776, buflen=131072

(The cause of this was misuse of the libext2fs extent code)

Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
---
 misc/fuse2fs.c |   73 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 misc/fuse4fs.c |   73 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 146 insertions(+)


diff --git a/misc/fuse2fs.c b/misc/fuse2fs.c
index 1dda9c45cb5089..4a9fda62f99bc2 100644
--- a/misc/fuse2fs.c
+++ b/misc/fuse2fs.c
@@ -578,6 +578,74 @@ static inline int fuse2fs_iomap_enabled(const struct fuse2fs *ff)
 # define fuse2fs_iomap_enabled(...)	(0)
 #endif
 
+static inline void fuse2fs_dump_extents(struct fuse2fs *ff, ext2_ino_t ino,
+					struct ext2_inode_large *inode,
+					const char *why)
+{
+	ext2_filsys fs = ff->fs;
+	unsigned int nr = 0;
+	blk64_t blockcount = 0;
+	struct ext2_inode_large xinode;
+	struct ext2fs_extent extent;
+	ext2_extent_handle_t extents;
+	int op = EXT2_EXTENT_ROOT;
+	errcode_t retval;
+
+	if (!inode) {
+		inode = &xinode;
+
+		retval = fuse2fs_read_inode(fs, ino, inode);
+		if (retval) {
+			com_err(__func__, retval, _("reading ino %u"), ino);
+			return;
+		}
+	}
+
+	if (!(inode->i_flags & EXT4_EXTENTS_FL))
+		return;
+
+	printf("%s: %s ino=%u isize %llu iblocks %llu\n", __func__, why, ino,
+	       EXT2_I_SIZE(inode),
+	       (ext2fs_get_stat_i_blocks(fs, EXT2_INODE(inode)) * 512) /
+	        fs->blocksize);
+	fflush(stdout);
+
+	retval = ext2fs_extent_open(fs, ino, &extents);
+	if (retval) {
+		com_err(__func__, retval, _("opening extents of ino \"%u\""),
+			ino);
+		return;
+	}
+
+	while ((retval = ext2fs_extent_get(extents, op, &extent)) == 0) {
+		op = EXT2_EXTENT_NEXT;
+
+		if (extent.e_flags & EXT2_EXTENT_FLAGS_SECOND_VISIT)
+			continue;
+
+		printf("[%u]: %s ino=%u lblk 0x%llx pblk 0x%llx len 0x%x flags 0x%x\n",
+		       nr++, why, ino, extent.e_lblk, extent.e_pblk,
+		       extent.e_len, extent.e_flags);
+		fflush(stdout);
+		if (extent.e_flags & EXT2_EXTENT_FLAGS_LEAF)
+			blockcount += extent.e_len;
+		else
+			blockcount++;
+	}
+	if (retval == EXT2_ET_EXTENT_NO_NEXT)
+		retval = 0;
+	if (retval) {
+		com_err(__func__, retval, ("getting extents of ino %u"),
+			ino);
+	}
+	if (inode->i_file_acl)
+		blockcount++;
+	printf("%s: %s sum(e_len) %llu\n", __func__, why, blockcount);
+	fflush(stdout);
+
+	ext2fs_extent_free(extents);
+}
+
 static void get_now(struct timespec *now)
 {
 #ifdef CLOCK_REALTIME
@@ -5433,6 +5501,11 @@ static int op_iomap_begin(const char *path, uint64_t nodeid, uint64_t attr_ino,
 		   (unsigned long long)read->length,
 		   read->type);
 
+	/* Not filling even the first byte will make the kernel unhappy. */
+	if (ff->debug && (read->offset > pos ||
+			  read->offset + read->length <= pos))
+		fuse2fs_dump_extents(ff, attr_ino, &inode, "BAD DATA");
+
 out_unlock:
 	fuse2fs_finish(ff, ret);
 	return ret;
diff --git a/misc/fuse4fs.c b/misc/fuse4fs.c
index 2aa7ab646592e9..0ac5de90498dac 100644
--- a/misc/fuse4fs.c
+++ b/misc/fuse4fs.c
@@ -730,6 +730,74 @@ static inline int fuse4fs_iomap_enabled(const struct fuse4fs *ff)
 # define fuse4fs_iomap_enabled(...)	(0)
 #endif
 
+static inline void fuse4fs_dump_extents(struct fuse4fs *ff, ext2_ino_t ino,
+					struct ext2_inode_large *inode,
+					const char *why)
+{
+	ext2_filsys fs = ff->fs;
+	unsigned int nr = 0;
+	blk64_t blockcount = 0;
+	struct ext2_inode_large xinode;
+	struct ext2fs_extent extent;
+	ext2_extent_handle_t extents;
+	int op = EXT2_EXTENT_ROOT;
+	errcode_t retval;
+
+	if (!inode) {
+		inode = &xinode;
+
+		retval = fuse4fs_read_inode(fs, ino, inode);
+		if (retval) {
+			com_err(__func__, retval, _("reading ino %u"), ino);
+			return;
+		}
+	}
+
+	if (!(inode->i_flags & EXT4_EXTENTS_FL))
+		return;
+
+	printf("%s: %s ino=%u isize %llu iblocks %llu\n", __func__, why, ino,
+	       EXT2_I_SIZE(inode),
+	       (ext2fs_get_stat_i_blocks(fs, EXT2_INODE(inode)) * 512) /
+	        fs->blocksize);
+	fflush(stdout);
+
+	retval = ext2fs_extent_open(fs, ino, &extents);
+	if (retval) {
+		com_err(__func__, retval, _("opening extents of ino \"%u\""),
+			ino);
+		return;
+	}
+
+	while ((retval = ext2fs_extent_get(extents, op, &extent)) == 0) {
+		op = EXT2_EXTENT_NEXT;
+
+		if (extent.e_flags & EXT2_EXTENT_FLAGS_SECOND_VISIT)
+			continue;
+
+		printf("[%u]: %s ino=%u lblk 0x%llx pblk 0x%llx len 0x%x flags 0x%x\n",
+		       nr++, why, ino, extent.e_lblk, extent.e_pblk,
+		       extent.e_len, extent.e_flags);
+		fflush(stdout);
+		if (extent.e_flags & EXT2_EXTENT_FLAGS_LEAF)
+			blockcount += extent.e_len;
+		else
+			blockcount++;
+	}
+	if (retval == EXT2_ET_EXTENT_NO_NEXT)
+		retval = 0;
+	if (retval) {
+		com_err(__func__, retval, ("getting extents of ino %u"),
+			ino);
+	}
+	if (inode->i_file_acl)
+		blockcount++;
+	printf("%s: %s sum(e_len) %llu\n", __func__, why, blockcount);
+	fflush(stdout);
+
+	ext2fs_extent_free(extents);
+}
+
 static void get_now(struct timespec *now)
 {
 #ifdef CLOCK_REALTIME
@@ -5839,6 +5907,11 @@ static void op_iomap_begin(fuse_req_t req, fuse_ino_t fino, uint64_t dontcare,
 		   read.type,
 		   read.flags);
 
+	/* Not filling even the first byte will make the kernel unhappy. */
+	if (ff->debug && (read.offset > pos ||
+			  read.offset + read.length <= pos))
+		fuse4fs_dump_extents(ff, ino, &inode, "BAD DATA");
+
 out_unlock:
 	fuse4fs_finish(ff, ret);
 	if (ret)