As we appear to have agreed that adding symlink support to debugfs via a new
ext2fs_symlink() function in libext2fs was something that needed doing, I
thought I'd use this as a trial run for my first contribution to the ext2fsprogs
package before I continue working on the larger project of completing initial
directory support for mke2fs.
While I modeled this patch after existing code, their were some inconcsistencies
in the code examples I used that I'd welcome input on. In particular:
o Should the ext2fs_link() happen right after ext2fs_new_inode()? Or should it
happen closer to the end of the operation? do_write() and ext2fs_mkdir()
handle this differently.
o Is it necessary to allocate the first block and assign it to the inode or the
extents? ext2fs_mkdir() does this, do_write() does not. I opted for the
simpler of the two and it passes my initial simple tests.
o Should I pass "mode" to ext2fs_new_inode() even though it is ignored?
o Would it make sense to try once to expand_dir rather than bailing out of
ext2fs_mkdir() and ext2fs_symlink() if the directory is full?
o What would we like the initial uid,gid,mode,*time values to be for
files/directories/links/etc. created with libext2fs?
Finally, I made an attempt to follow the coding style I observed in the code,
but if I missed something, please let me know.
Thanks,
Darren Hart
Intel Open Source Technology Center
Just a typo fix.
Signed-off-by: Darren Hart <[email protected]>
Cc: "Theodore Ts'o" <[email protected]>
Cc: Andreas Dilger <[email protected]>
---
doc/libext2fs.texinfo | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/doc/libext2fs.texinfo b/doc/libext2fs.texinfo
index 9d8e7f1..8272d1d 100644
--- a/doc/libext2fs.texinfo
+++ b/doc/libext2fs.texinfo
@@ -767,7 +767,7 @@ to initialize directory entries for @file{.} and @file{..}, respectively.
@deftypefun errcode_t ext2fs_dir_iterate (ext2_filsys @var{fs}, ext2_ino_t @var{dir}, int @var{flags}, char *@var{block_buf}, int (*@var{func})(struct ext2_dir_entry *@var{dirent}, int @var{offset}, int @var{blocksize}, char *@var{buf}, void *@var{private}), void *@var{private})
-This function interates over all of the directory entries in the
+This function iterates over all of the directory entries in the
directory @var{dir}, calling the callback function @var{func} for each
directory entry in the directory. The @var{block_buf} parameter should
either be NULL, or if the @code{ext2fs_dir_iterate} function is
--
1.7.11.7
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 <[email protected]>
Cc: "Theodore Ts'o" <[email protected]>
Cc: Andreas Dilger <[email protected]>
---
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
Add support for symbolic links using a new symlink command.
Modeled after the do_mkdir() command.
Very long target paths fail as the command parsing appears to truncate the
input to somewhere around 256 bytes. Independent testing of the
ext2fs_symlink() command demonstrates it works with multi-block-length
pathes.
Signed-off-by: Darren Hart <[email protected]>
Cc: "Theodore Ts'o" <[email protected]>
Cc: Andreas Dilger <[email protected]>
---
debugfs/debug_cmds.ct | 3 +++
debugfs/debugfs.8.in | 3 +++
debugfs/debugfs.c | 43 +++++++++++++++++++++++++++++++++++++++++++
debugfs/debugfs.h | 1 +
debugfs/dump.c | 2 +-
5 files changed, 51 insertions(+), 1 deletion(-)
diff --git a/debugfs/debug_cmds.ct b/debugfs/debug_cmds.ct
index a799dd7..338192f 100644
--- a/debugfs/debug_cmds.ct
+++ b/debugfs/debug_cmds.ct
@@ -160,6 +160,9 @@ request do_bmap, "Calculate the logical->physical block mapping for an inode",
request do_punch, "Punch (or truncate) blocks from an inode by deallocating them",
punch, truncate;
+request do_symlink, "Create a symbolic link",
+ symlink;
+
request do_imap, "Calculate the location of an inode",
imap;
diff --git a/debugfs/debugfs.8.in b/debugfs/debugfs.8.in
index bfcb1a8..c3b49f9 100644
--- a/debugfs/debugfs.8.in
+++ b/debugfs/debugfs.8.in
@@ -469,6 +469,9 @@ is, all of the blocks starting at
.I start_blk
through to the end of the file will be deallocated.
.TP
+.I symlink filespec target
+Make a symbolic link.
+.TP
.I pwd
Print the current working directory.
.TP
diff --git a/debugfs/debugfs.c b/debugfs/debugfs.c
index aec61ab..6c4c1b1 100644
--- a/debugfs/debugfs.c
+++ b/debugfs/debugfs.c
@@ -2204,6 +2204,49 @@ void do_punch(int argc, char *argv[])
}
#endif /* READ_ONLY */
+void do_symlink(int argc, char *argv[])
+{
+ char *cp;
+ ext2_ino_t parent;
+ char *name, *target;
+ errcode_t retval;
+
+ if (common_args_process(argc, argv, 3, 3, "symlink",
+ "<filename> <target>", CHECK_FS_RW))
+ return;
+
+ cp = strrchr(argv[1], '/');
+ if (cp) {
+ *cp = 0;
+ parent = string_to_inode(argv[1]);
+ if (!parent) {
+ com_err(argv[1], ENOENT, 0);
+ return;
+ }
+ name = cp+1;
+ } else {
+ parent = cwd;
+ name = argv[1];
+ }
+ target = argv[2];
+
+try_again:
+ retval = ext2fs_symlink(current_fs, parent, 0, name, target);
+ if (retval == EXT2_ET_DIR_NO_SPACE) {
+ retval = ext2fs_expand_dir(current_fs, parent);
+ if (retval) {
+ com_err(argv[0], retval, "while expanding directory");
+ return;
+ }
+ goto try_again;
+ }
+ if (retval) {
+ com_err("ext2fs_symlink", retval, 0);
+ return;
+ }
+
+}
+
void do_dump_mmp(int argc EXT2FS_ATTR((unused)), char *argv[])
{
#if CONFIG_MMP
diff --git a/debugfs/debugfs.h b/debugfs/debugfs.h
index 994577c..434dbf0 100644
--- a/debugfs/debugfs.h
+++ b/debugfs/debugfs.h
@@ -133,6 +133,7 @@ extern void do_imap(int argc, char **argv);
extern void do_set_current_time(int argc, char **argv);
extern void do_supported_features(int argc, char **argv);
extern void do_punch(int argc, char **argv);
+extern void do_symlink(int argc, char **argv);
extern void do_dump_mmp(int argc, char **argv);
extern void do_set_mmp_value(int argc, char **argv);
diff --git a/debugfs/dump.c b/debugfs/dump.c
index a15a0b7..2d830c9 100644
--- a/debugfs/dump.c
+++ b/debugfs/dump.c
@@ -285,7 +285,7 @@ static void rdump_inode(ext2_ino_t ino, struct ext2_inode *inode,
fix_perms("rdump", inode, -1, fullname);
}
- /* else do nothing (don't dump device files, sockets, fifos, etc.) */
+ /* else do nothing (don't dump device files, sockets, fifos, symlinks, etc.) */
errout:
free(fullname);
--
1.7.11.7
Just a bump as a reminder so this series doesn't drop off the Inbox
queue :-)
Thanks,
Darren
On 12/05/2012 01:56 PM, Darren Hart wrote:
> As we appear to have agreed that adding symlink support to debugfs via a new
> ext2fs_symlink() function in libext2fs was something that needed doing, I
> thought I'd use this as a trial run for my first contribution to the ext2fsprogs
> package before I continue working on the larger project of completing initial
> directory support for mke2fs.
>
> While I modeled this patch after existing code, their were some inconcsistencies
> in the code examples I used that I'd welcome input on. In particular:
>
> o Should the ext2fs_link() happen right after ext2fs_new_inode()? Or should it
> happen closer to the end of the operation? do_write() and ext2fs_mkdir()
> handle this differently.
>
> o Is it necessary to allocate the first block and assign it to the inode or the
> extents? ext2fs_mkdir() does this, do_write() does not. I opted for the
> simpler of the two and it passes my initial simple tests.
>
> o Should I pass "mode" to ext2fs_new_inode() even though it is ignored?
>
> o Would it make sense to try once to expand_dir rather than bailing out of
> ext2fs_mkdir() and ext2fs_symlink() if the directory is full?
>
> o What would we like the initial uid,gid,mode,*time values to be for
> files/directories/links/etc. created with libext2fs?
>
> Finally, I made an attempt to follow the coding style I observed in the code,
> but if I missed something, please let me know.
>
> Thanks,
>
> Darren Hart
> Intel Open Source Technology Center
> --
> To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
> the body of a message to [email protected]
> More majordomo info at http://vger.kernel.org/majordomo-info.html
>
--
Darren Hart
Intel Open Source Technology Center
Yocto Project - Technical Lead - Linux Kernel