NTFS: More runlist handling fixes from Richard Russon and myself.

Signed-off-by: Anton Altaparmakov <aia21@cantab.net>

diff --git a/fs/ntfs/runlist.c b/fs/ntfs/runlist.c
index e2665d011d72ce4d8869aaf5c4b66736ae2b1d0f..061b5ff6b73cec10f317f566cd3dc6fa8512e9d9 100644 (file)
--- a/fs/ntfs/runlist.c
+++ b/fs/ntfs/runlist.c
@@ -158,17 +158,21 @@ static inline BOOL ntfs_are_rl_mergeable(runlist_element *dst,
        BUG_ON(!dst);
        BUG_ON(!src);
 
-       if ((dst->lcn < 0) || (src->lcn < 0)) {   /* Are we merging holes? */
-               if (dst->lcn == LCN_HOLE && src->lcn == LCN_HOLE)
-                       return TRUE;
+       /* We can merge unmapped regions even if they are misaligned. */
+       if ((dst->lcn == LCN_RL_NOT_MAPPED) && (src->lcn == LCN_RL_NOT_MAPPED))
+               return TRUE;
+       /* If the runs are misaligned, we cannot merge them. */
+       if ((dst->vcn + dst->length) != src->vcn)
                return FALSE;
-       }
-       if ((dst->lcn + dst->length) != src->lcn) /* Are the runs contiguous? */
-               return FALSE;
-       if ((dst->vcn + dst->length) != src->vcn) /* Are the runs misaligned? */
-               return FALSE;
-
-       return TRUE;
+       /* If both runs are non-sparse and contiguous, we can merge them. */
+       if ((dst->lcn >= 0) && (src->lcn >= 0) &&
+                       ((dst->lcn + dst->length) == src->lcn))
+               return TRUE;
+       /* If we are merging two holes, we can merge them. */
+       if ((dst->lcn == LCN_HOLE) && (src->lcn == LCN_HOLE))
+               return TRUE;
+       /* Cannot merge. */
+       return FALSE;
 }
 
 /**
@@ -214,14 +218,15 @@ static inline void __ntfs_rl_merge(runlist_element *dst, runlist_element *src)
 static inline runlist_element *ntfs_rl_append(runlist_element *dst,
                int dsize, runlist_element *src, int ssize, int loc)
 {
-       BOOL right;     /* Right end of @src needs merging. */
-       int marker;     /* End of the inserted runs. */
+       BOOL right = FALSE;     /* Right end of @src needs merging. */
+       int marker;             /* End of the inserted runs. */
 
        BUG_ON(!dst);
        BUG_ON(!src);
 
        /* First, check if the right hand end needs merging. */
-       right = ntfs_are_rl_mergeable(src + ssize - 1, dst + loc + 1);
+       if ((loc + 1) < dsize)
+               right = ntfs_are_rl_mergeable(src + ssize - 1, dst + loc + 1);
 
        /* Space required: @dst size + @src size, less one if we merged. */
        dst = ntfs_rl_realloc(dst, dsize, dsize + ssize - right);
@@ -377,20 +382,21 @@ static inline runlist_element *ntfs_rl_replace(runlist_element *dst,
                int dsize, runlist_element *src, int ssize, int loc)
 {
        BOOL left = FALSE;      /* Left end of @src needs merging. */
-       BOOL right;             /* Right end of @src needs merging. */
+       BOOL right = FALSE;     /* Right end of @src needs merging. */
        int tail;               /* Start of tail of @dst. */
        int marker;             /* End of the inserted runs. */
 
        BUG_ON(!dst);
        BUG_ON(!src);
 
-       /* First, merge the left and right ends, if necessary. */
-       right = ntfs_are_rl_mergeable(src + ssize - 1, dst + loc + 1);
+       /* First, see if the left and right ends need merging. */
+       if ((loc + 1) < dsize)
+               right = ntfs_are_rl_mergeable(src + ssize - 1, dst + loc + 1);
        if (loc > 0)
                left = ntfs_are_rl_mergeable(dst + loc - 1, src);
        /*
         * Allocate some space.  We will need less if the left, right, or both
-        * ends were merged.
+        * ends get merged.
         */
        dst = ntfs_rl_realloc(dst, dsize, dsize + ssize - left - right);
        if (IS_ERR(dst))
@@ -399,21 +405,26 @@ static inline runlist_element *ntfs_rl_replace(runlist_element *dst,
         * We are guaranteed to succeed from here so can start modifying the
         * original runlists.
         */
+
+       /* First, merge the left and right ends, if necessary. */
        if (right)
                __ntfs_rl_merge(src + ssize - 1, dst + loc + 1);
        if (left)
                __ntfs_rl_merge(dst + loc - 1, src);
        /*
-        * First run of @dst that needs to be moved out of the way to make
-        * space for the runs to be copied from @src, i.e. the first run of the
-        * tail of @dst.
+        * Offset of the tail of @dst.  This needs to be moved out of the way
+        * to make space for the runs to be copied from @src, i.e. the first
+        * run of the tail of @dst.
+        * Nominally, @tail equals @loc + 1, i.e. location, skipping the
+        * replaced run.  However, if @right, then one of @dst's runs is
+        * already merged into @src.
         */
        tail = loc + right + 1;
        /*
         * First run after the @src runs that have been inserted, i.e. where
         * the tail of @dst needs to be moved to.
-        * Nominally, marker equals @loc + @ssize, i.e. location + number of
-        * runs in @src).  However, if @left, then the first run in @src has
+        * Nominally, @marker equals @loc + @ssize, i.e. location + number of
+        * runs in @src.  However, if @left, then the first run in @src has
         * been merged with one in @dst.
         */
        marker = loc + ssize - left;