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Date: Wed, 19 Dec 2012 18:49:22 -0800
From: Darren Hart <dvhart@...radead.org>
To: linux-ext4@...r.kernel.org
Cc: tytso@....edu, adilger@...ger.ca, sgw@...ux.intel.com,
Darren Hart <dvhart@...radead.org>
Subject: [PATCH 2/3] lib/ext2fs: Add ext2fs_symlink
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@...radead.org>
Cc: "Theodore Ts'o" <tytso@....edu>
Cc: Andreas Dilger <adilger@...ger.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
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;
+}
--
1.7.11.7
--
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