ext4: miscellaneous partial cluster cleanups

Add some casts and rearrange a few statements for improved readability.
Some code can also be simplified and made more readable if we set
partial_cluster to 0 rather than to a negative value when we can tell
we've hit the left edge of the punched region.

Signed-off-by: Eric Whitney <enwlinux@gmail.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 859ab37..841adf0 100644 (file)
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -2481,7 +2481,7 @@ static int ext4_remove_blocks(handle_t *handle, struct inode *inode,
                              ext4_lblk_t from, ext4_lblk_t to)
 {
        struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
-       unsigned short ee_len =  ext4_ext_get_actual_len(ex);
+       unsigned short ee_len = ext4_ext_get_actual_len(ex);
        ext4_fsblk_t pblk;
        int flags = get_default_free_blocks_flags(inode);
 
@@ -2490,7 +2490,7 @@ static int ext4_remove_blocks(handle_t *handle, struct inode *inode,
         * at the beginning of the extent.  Instead, we make a note
         * that we tried freeing the cluster, and check to see if we
         * need to free it on a subsequent call to ext4_remove_blocks,
-        * or at the end of the ext4_truncate() operation.
+        * or at the end of ext4_ext_rm_leaf or ext4_ext_remove_space.
         */
        flags |= EXT4_FREE_BLOCKS_NOFREE_FIRST_CLUSTER;
 
@@ -2501,8 +2501,8 @@ static int ext4_remove_blocks(handle_t *handle, struct inode *inode,
         * partial cluster here.
         */
        pblk = ext4_ext_pblock(ex) + ee_len - 1;
-       if ((*partial_cluster > 0) &&
-           (EXT4_B2C(sbi, pblk) != *partial_cluster)) {
+       if (*partial_cluster > 0 &&
+           *partial_cluster != (long long) EXT4_B2C(sbi, pblk)) {
                ext4_free_blocks(handle, inode, NULL,
                                 EXT4_C2B(sbi, *partial_cluster),
                                 sbi->s_cluster_ratio, flags);
@@ -2528,7 +2528,7 @@ static int ext4_remove_blocks(handle_t *handle, struct inode *inode,
            && to == le32_to_cpu(ex->ee_block) + ee_len - 1) {
                /* tail removal */
                ext4_lblk_t num;
-               unsigned int unaligned;
+               long long first_cluster;
 
                num = le32_to_cpu(ex->ee_block) + ee_len - from;
                pblk = ext4_ext_pblock(ex) + ee_len - num;
@@ -2538,7 +2538,7 @@ static int ext4_remove_blocks(handle_t *handle, struct inode *inode,
                 * used by any other extent (partial_cluster is negative).
                 */
                if (*partial_cluster < 0 &&
-                   -(*partial_cluster) == EXT4_B2C(sbi, pblk + num - 1))
+                   *partial_cluster == -(long long) EXT4_B2C(sbi, pblk+num-1))
                        flags |= EXT4_FREE_BLOCKS_NOFREE_LAST_CLUSTER;
 
                ext_debug("free last %u blocks starting %llu partial %lld\n",
@@ -2549,21 +2549,24 @@ static int ext4_remove_blocks(handle_t *handle, struct inode *inode,
                 * beginning of a cluster, and we removed the entire
                 * extent and the cluster is not used by any other extent,
                 * save the partial cluster here, since we might need to
-                * delete if we determine that the truncate operation has
-                * removed all of the blocks in the cluster.
+                * delete if we determine that the truncate or punch hole
+                * operation has removed all of the blocks in the cluster.
+                * If that cluster is used by another extent, preserve its
+                * negative value so it isn't freed later on.
                 *
-                * On the other hand, if we did not manage to free the whole
-                * extent, we have to mark the cluster as used (store negative
-                * cluster number in partial_cluster).
+                * If the whole extent wasn't freed, we've reached the
+                * start of the truncated/punched region and have finished
+                * removing blocks.  If there's a partial cluster here it's
+                * shared with the remainder of the extent and is no longer
+                * a candidate for removal.
                 */
-               unaligned = EXT4_PBLK_COFF(sbi, pblk);
-               if (unaligned && (ee_len == num) &&
-                   (*partial_cluster != -((long long)EXT4_B2C(sbi, pblk))))
-                       *partial_cluster = EXT4_B2C(sbi, pblk);
-               else if (unaligned)
-                       *partial_cluster = -((long long)EXT4_B2C(sbi, pblk));
-               else if (*partial_cluster > 0)
+               if (EXT4_PBLK_COFF(sbi, pblk) && ee_len == num) {
+                       first_cluster = (long long) EXT4_B2C(sbi, pblk);
+                       if (first_cluster != -*partial_cluster)
+                               *partial_cluster = first_cluster;
+               } else {
                        *partial_cluster = 0;
+               }
        } else
                ext4_error(sbi->s_sb, "strange request: removal(2) "
                           "%u-%u from %u:%u\n",