libext2fs: rewind extent pointer when totally deleting an extent

During a punch operation, if we decide to delete an extent out of the
extent tree, the subsequent extents are moved on top of the current
extent (that is to say, they're memmmove'd down one slot).  Therefore
it is not correct to advance to the next leaf because that means we
miss half the extents in the range!  Rereading the current pointer
should be fine.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

diff --git a/lib/ext2fs/punch.c b/lib/ext2fs/punch.c
index b53653a..11c7668 100644 (file)
--- a/lib/ext2fs/punch.c
+++ b/lib/ext2fs/punch.c
@@ -186,6 +186,7 @@ static errcode_t ext2fs_punch_extent(ext2_filsys fs, ext2_ino_t ino,
        blk64_t                 free_start, next;
        __u32                   free_count, newlen;
        int                     freed = 0;
+       int                     op;
 
        retval = ext2fs_extent_open2(fs, ino, inode, &handle);
        if (retval)
@@ -195,6 +196,7 @@ static errcode_t ext2fs_punch_extent(ext2_filsys fs, ext2_ino_t ino,
        if (retval)
                goto errout;
        while (1) {
+               op = EXT2_EXTENT_NEXT_LEAF;
                dbg_print_extent("main loop", &extent);
                next = extent.e_lblk + extent.e_len;
                dbg_printf("start %llu, end %llu, next %llu\n",
@@ -256,8 +258,23 @@ static errcode_t ext2fs_punch_extent(ext2_filsys fs, ext2_ino_t ino,
                        dbg_print_extent("replacing", &extent);
                        retval = ext2fs_extent_replace(handle, 0, &extent);
                } else {
+                       struct ext2fs_extent    newex;
                        dbg_printf("deleting current extent%s\n", "");
                        retval = ext2fs_extent_delete(handle, 0);
+                       if (retval)
+                               goto errout;
+                       /*
+                        * We just moved the next extent into the current
+                        * extent's position, so re-read the extent next time.
+                        */
+                       retval = ext2fs_extent_get(handle,
+                                                  EXT2_EXTENT_PREV_LEAF,
+                                                  &newex);
+                       /* Can't go back? Just reread current. */
+                       if (retval == EXT2_ET_EXTENT_NO_PREV) {
+                               retval = 0;
+                               op = EXT2_EXTENT_CURRENT;
+                       }
                }
                if (retval)
                        goto errout;
@@ -268,9 +285,10 @@ static errcode_t ext2fs_punch_extent(ext2_filsys fs, ext2_ino_t ino,
                        freed++;
                }
        next_extent:
-               retval = ext2fs_extent_get(handle, EXT2_EXTENT_NEXT_LEAF,
+               retval = ext2fs_extent_get(handle, op,
                                           &extent);
-               if (retval == EXT2_ET_EXTENT_NO_NEXT)
+               if (retval == EXT2_ET_EXTENT_NO_NEXT ||
+                   retval == EXT2_ET_NO_CURRENT_NODE)
                        break;
                if (retval)
                        goto errout;