e2undo: support the undo header's fs_offset feature

If the fs_offset feature is present (and no "-o offset"
option is specified), e2undo performs the undo operation at
the stored offset.

Signed-off-by: Marcus Huewe <suse-tux@gmx.de>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/misc/e2undo.c b/misc/e2undo.c
index 4ea78cc..9ef3d96 100644 (file)
--- a/misc/e2undo.c
+++ b/misc/e2undo.c
@@ -62,7 +62,9 @@ struct undo_header {
        __le32 f_compat;        /* compatible features (none so far) */
        __le32 f_incompat;      /* incompatible features (none so far) */
        __le32 f_rocompat;      /* ro compatible features (none so far) */
-       __u8 padding[448];      /* padding */
+       __le32 pad32;           /* padding for fs_offset */
+       __le64 fs_offset;       /* filesystem offset */
+       __u8 padding[436];      /* padding */
        __le32 header_crc;      /* crc32c of the header (but not this field) */
 };
 
@@ -99,6 +101,13 @@ struct undo_context {
 };
 #define KEYS_PER_BLOCK(d) (((d)->blocksize / sizeof(struct undo_key)) - 1)
 
+#define E2UNDO_FEATURE_COMPAT_FS_OFFSET 0x1    /* the filesystem offset */
+
+static inline int e2undo_has_feature_fs_offset(struct undo_header *header) {
+       return ext2fs_le32_to_cpu(header->f_compat) &
+               E2UNDO_FEATURE_COMPAT_FS_OFFSET;
+}
+
 static char *prg_name;
 static char *undo_file;
 
@@ -121,6 +130,8 @@ static void dump_header(struct undo_header *hdr)
        printf("compat:\t\t0x%x\n", ext2fs_le32_to_cpu(hdr->f_compat));
        printf("incompat:\t0x%x\n", ext2fs_le32_to_cpu(hdr->f_incompat));
        printf("rocompat:\t0x%x\n", ext2fs_le32_to_cpu(hdr->f_rocompat));
+       if (e2undo_has_feature_fs_offset(hdr))
+               printf("fs offset:\t%llu\n", ext2fs_le64_to_cpu(hdr->fs_offset));
        printf("header crc:\t0x%x\n", ext2fs_le32_to_cpu(hdr->header_crc));
 }
 
@@ -399,8 +410,12 @@ int main(int argc, char *argv[])
        undo_ctx.super_block = ext2fs_le64_to_cpu(undo_ctx.hdr.super_offset);
        undo_ctx.num_keys = ext2fs_le64_to_cpu(undo_ctx.hdr.num_keys);
        io_channel_set_blksize(undo_ctx.undo_file, undo_ctx.blocksize);
-       if (!force && (undo_ctx.hdr.f_compat || undo_ctx.hdr.f_incompat ||
-                      undo_ctx.hdr.f_rocompat)) {
+       /*
+        * Do not compare undo_ctx.hdr.f_compat with the available compatible
+        * features set, because a "missing" compatible feature should
+        * not cause any problems.
+        */
+       if (!force && (undo_ctx.hdr.f_incompat || undo_ctx.hdr.f_rocompat)) {
                fprintf(stderr, _("%s: Unknown undo file feature set.\n"),
                        tdb_file);
                exit(1);
@@ -435,7 +450,9 @@ int main(int argc, char *argv[])
                exit(1);
        }
 
-       if (*opt_offset_string) {
+       if (*opt_offset_string || e2undo_has_feature_fs_offset(&undo_ctx.hdr)) {
+               if (!*opt_offset_string)
+                       offset = ext2fs_le64_to_cpu(undo_ctx.hdr.fs_offset);
                retval = snprintf(opt_offset_string, sizeof(opt_offset_string),
                                                  "offset=%llu", offset);
                if (retval >= sizeof(opt_offset_string)) {