Patchwork [2/3] lib/ext2fs: Add ext2fs_symlink

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Submitter Darren Hart
Date Dec. 5, 2012, 9:56 p.m.
Message ID <40709903834127afbb1f6eda82cf50c292b3f97c.1354743799.git.dvhart@infradead.org>
Download mbox | patch
Permalink /patch/203972/
State Superseded
Headers show

Comments

Darren Hart - Dec. 5, 2012, 9:56 p.m.
Creating symlinks is a complex affair when accounting for slowlinks.

Create a new function, ext2fs_symlink(), modeled after ext2fs_mkdir()
with input from debugfs's do_write() and copy_file(). Like
ext2fs_mkdir(), ext2fs_symlink() takes on the task of allocating a new
inode, setting up sane default values in the inode, accounting for the
inode stats, and copying the target path to either the inode (for
fastlinks) or to the blocks/extents (for slowlinks) using
ext2fs_file_write().

It does not attempt to expand the parent directory, instead returning
EXT2_ET_DIR_NO_SPACE and leaving it to the caller to expand just as
ext2fs_mkdir() does. Ideally, I think both of these functions should
make a single attempt to expand the directory.

Adds 1556 bytes to libext2fs.a (stripped).

Signed-off-by: Darren Hart <dvhart@infradead.org>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Andreas Dilger <adilger@dilger.ca>
---
 lib/ext2fs/Makefile.in    |   8 +++
 lib/ext2fs/ext2_err.et.in |   3 +
 lib/ext2fs/symlink.c      | 137 ++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 148 insertions(+)
 create mode 100644 lib/ext2fs/symlink.c

Patch

diff --git a/lib/ext2fs/Makefile.in b/lib/ext2fs/Makefile.in
index e05b438..5411826 100644
--- a/lib/ext2fs/Makefile.in
+++ b/lib/ext2fs/Makefile.in
@@ -80,6 +80,7 @@  OBJS= $(DEBUGFS_LIB_OBJS) $(RESIZE_LIB_OBJS) $(E2IMAGE_LIB_OBJS) \
 	res_gdt.o \
 	rw_bitmaps.o \
 	swapfs.o \
+	symlink.o \
 	tdb.o \
 	undo_io.o \
 	unix_io.o \
@@ -155,6 +156,7 @@  SRCS= ext2_err.c \
 	$(srcdir)/res_gdt.c \
 	$(srcdir)/rw_bitmaps.c \
 	$(srcdir)/swapfs.c \
+	$(srcdir)/symlink.c \
 	$(srcdir)/tdb.c \
 	$(srcdir)/test_io.c \
 	$(srcdir)/tst_badblocks.c \
@@ -881,6 +883,12 @@  swapfs.o: $(srcdir)/swapfs.c $(top_builddir)/lib/config.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
+symlink.o: $(srcdir)/symlink.c $(top_builddir)/lib/config.h \
+ $(top_builddir)/lib/dirpaths.h $(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
 tdb.o: $(srcdir)/tdb.c $(top_builddir)/lib/config.h \
  $(top_builddir)/lib/dirpaths.h $(srcdir)/tdb.h
 test_io.o: $(srcdir)/test_io.c $(top_builddir)/lib/config.h \
diff --git a/lib/ext2fs/ext2_err.et.in b/lib/ext2fs/ext2_err.et.in
index c99a167..e1313a8 100644
--- a/lib/ext2fs/ext2_err.et.in
+++ b/lib/ext2fs/ext2_err.et.in
@@ -248,6 +248,9 @@  ec	EXT2_ET_DB_NOT_FOUND,
 ec	EXT2_ET_DIR_EXISTS,
 	"Ext2 directory already exists"
 
+ec	EXT2_ET_FILE_EXISTS,
+	"Ext2 file already exists"
+
 ec	EXT2_ET_UNIMPLEMENTED,
 	"Unimplemented ext2 library function"
 
diff --git a/lib/ext2fs/symlink.c b/lib/ext2fs/symlink.c
new file mode 100644
index 0000000..5bfb9fc
--- /dev/null
+++ b/lib/ext2fs/symlink.c
@@ -0,0 +1,137 @@ 
+/*
+ * symlink.c --- make a symlink in the filesystem, based on mkdir.c
+ *
+ * Copyright (c) 2012, Intel Corporation.
+ * All Rights Reserved.
+ *
+ * %Begin-Header%
+ * This file may be redistributed under the terms of the GNU Library
+ * General Public License, version 2.
+ * %End-Header%
+ */
+
+#include "config.h"
+#include <stdio.h>
+#include <string.h>
+#if HAVE_UNISTD_H
+#include <unistd.h>
+#endif
+#include <fcntl.h>
+#include <time.h>
+#if HAVE_SYS_STAT_H
+#include <sys/stat.h>
+#endif
+#if HAVE_SYS_TYPES_H
+#include <sys/types.h>
+#endif
+
+#include "ext2_fs.h"
+#include "ext2fs.h"
+
+#ifndef EXT2_FT_SYMLINK
+#define EXT2_FT_SYMLINK		7
+#endif
+
+errcode_t ext2fs_symlink(ext2_filsys fs, ext2_ino_t parent, ext2_ino_t ino,
+                         const char *name, char *target)
+{
+	ext2_extent_handle_t	handle;
+	errcode_t		retval;
+	struct ext2_inode	inode;
+	ext2_ino_t		scratch_ino;
+	int			fastlink;
+	int			target_len;
+
+	EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);
+
+	/*
+	 * Allocate an inode, if necessary
+	 */
+	if (!ino) {
+		retval = ext2fs_new_inode(fs, parent, LINUX_S_IFLNK | 0755,
+		                          0, &ino);
+		if (retval)
+			goto cleanup;
+	}
+
+	/*
+	 * Link the symlink into the filesystem hierarchy
+	 */
+	retval = ext2fs_lookup(fs, parent, name, strlen(name), 0,
+	                       &scratch_ino);
+	if (!retval) {
+		retval = EXT2_ET_FILE_EXISTS;
+		goto cleanup;
+	}
+	if (retval != EXT2_ET_FILE_NOT_FOUND)
+		goto cleanup;
+	retval = ext2fs_link(fs, parent, name, ino, EXT2_FT_SYMLINK);
+	if (retval)
+		goto cleanup;
+
+	ext2fs_inode_alloc_stats2(fs, ino, +1, 1);
+
+	/*
+	 * Create the inode structure....
+	 */
+	memset(&inode, 0, sizeof(struct ext2_inode));
+	inode.i_mode = LINUX_S_IFLNK | 0777;
+	inode.i_uid = inode.i_gid = 0;
+	/* FIXME: set the time fields */
+	inode.i_links_count = 1;
+
+	target_len = strlen(target);
+	fastlink = (target_len < sizeof(inode.i_block));
+	if (fastlink) {
+		/* Fast symlinks, target stored in inode */
+		inode.i_size = target_len;
+		strcpy((char *)&inode.i_block, target);
+	} else {
+		if (retval)
+			goto cleanup;
+
+		if (fs->super->s_feature_incompat & EXT3_FEATURE_INCOMPAT_EXTENTS)
+			inode.i_flags |= EXT4_EXTENTS_FL;
+
+		inode.i_size = (target_len % fs->blocksize) ?
+		               target_len + (fs->blocksize - target_len) : target_len;
+	}
+
+	/*
+	 * Write out the inode and inode data block.  The inode generation
+	 * number is assigned by write_new_inode, which means that the file
+	 * operations below should come after it.
+	 */
+	retval = ext2fs_write_new_inode(fs, ino, &inode);
+	if (retval)
+		goto cleanup;
+
+	/*
+	 * For slow links, the target path is written to the blocks/extents
+	 */
+	if (!fastlink) {
+		ext2_extent_handle_t handle;
+		ext2_file_t file;
+		int written = 0;
+		char *rem;
+
+		/* Write the target to file */
+		retval = ext2fs_file_open2(fs, ino, &inode,
+		                           EXT2_FILE_CREATE | EXT2_FILE_WRITE,
+		                           &file);
+		if (retval)
+			goto cleanup;
+
+		rem = target;
+		while (strlen(rem)) {
+			retval = ext2fs_file_write(file, (void *)rem, strlen(rem), &written);
+			rem += written;
+			if (retval)
+				break;
+		}
+		ext2fs_file_close(file);
+	}
+
+cleanup:
+	return retval;
+}