NTFS: Use ntfs_malloc_nofs_nofail() in runlist.c::ntfs_runlists_merge()

      in the two critical regions.  This means we no longer need to
      panic() when the allocation fails as it now cannot fail.

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

2 files changed, 53 insertions, 18 deletions

diff --git a/fs/ntfs/ChangeLog b/fs/ntfs/ChangeLog
index c3bf17be0e19..c5bbedff5ae5 100644
--- a/fs/ntfs/ChangeLog
+++ b/fs/ntfs/ChangeLog
@@ -40,6 +40,9 @@ ToDo/Notes:
         - Add fs/ntfs/malloc.h::ntfs_malloc_nofs_nofail() which is analogous to
           ntfs_malloc_nofs() but it performs allocations with __GFP_NOFAIL and
           hence cannot fail.
+        - Use ntfs_malloc_nofs_nofail() in the two critical regions in
+          fs/ntfs/runlist.c::ntfs_runlists_merge().  This means we no longer
+          need to panic() if the allocation fails as it now cannot fail.
 
 2.1.23 - Implement extension of resident files and make writing safe as well as
          many bug fixes, cleanups, and enhancements...
diff --git a/fs/ntfs/runlist.c b/fs/ntfs/runlist.c
index 758855b0414e..3bb4a57d1fa9 100644
--- a/fs/ntfs/runlist.c
+++ b/fs/ntfs/runlist.c
@@ -35,7 +35,7 @@ static inline void ntfs_rl_mm(runlist_element *base, int dst, int src,
                 int size)
 {
         if (likely((dst != src) && (size > 0)))
-                memmove(base + dst, base + src, size * sizeof (*base));
+                memmove(base + dst, base + src, size * sizeof(*base));
 }
 
 /**
@@ -95,6 +95,51 @@ static inline runlist_element *ntfs_rl_realloc(runlist_element *rl,
 }
 
 /**
+ * ntfs_rl_realloc_nofail - Reallocate memory for runlists
+ * @rl:         original runlist
+ * @old_size:   number of runlist elements in the original runlist @rl
+ * @new_size:   number of runlist elements we need space for
+ *
+ * As the runlists grow, more memory will be required.  To prevent the
+ * kernel having to allocate and reallocate large numbers of small bits of
+ * memory, this function returns an entire page of memory.
+ *
+ * This function guarantees that the allocation will succeed.  It will sleep
+ * for as long as it takes to complete the allocation.
+ *
+ * It is up to the caller to serialize access to the runlist @rl.
+ *
+ * N.B.  If the new allocation doesn't require a different number of pages in
+ *       memory, the function will return the original pointer.
+ *
+ * On success, return a pointer to the newly allocated, or recycled, memory.
+ * On error, return -errno. The following error codes are defined:
+ *      -ENOMEM - Not enough memory to allocate runlist array.
+ *      -EINVAL - Invalid parameters were passed in.
+ */
+static inline runlist_element *ntfs_rl_realloc_nofail(runlist_element *rl,
+                int old_size, int new_size)
+{
+        runlist_element *new_rl;
+
+        old_size = PAGE_ALIGN(old_size * sizeof(*rl));
+        new_size = PAGE_ALIGN(new_size * sizeof(*rl));
+        if (old_size == new_size)
+                return rl;
+
+        new_rl = ntfs_malloc_nofs_nofail(new_size);
+        BUG_ON(!new_rl);
+
+        if (likely(rl != NULL)) {
+                if (unlikely(old_size > new_size))
+                        old_size = new_size;
+                memcpy(new_rl, rl, old_size);
+                ntfs_free(rl);
+        }
+        return new_rl;
+}
+
+/**
  * ntfs_are_rl_mergeable - test if two runlists can be joined together
  * @dst:        original runlist
  * @src:        new runlist to test for mergeability with @dst
@@ -621,11 +666,8 @@ runlist_element *ntfs_runlists_merge(runlist_element *drl,
                         if (drl[ds].lcn != LCN_RL_NOT_MAPPED) {
                                 /* Add an unmapped runlist element. */
                                 if (!slots) {
-                                        /* FIXME/TODO: We need to have the
-                                         * extra memory already! (AIA) */
-                                        drl = ntfs_rl_realloc(drl, ds, ds + 2);
-                                        if (!drl)
-                                                goto critical_error;
+                                        drl = ntfs_rl_realloc_nofail(drl, ds,
+                                                        ds + 2);
                                         slots = 2;
                                 }
                                 ds++;
@@ -640,13 +682,8 @@ runlist_element *ntfs_runlists_merge(runlist_element *drl,
                         drl[ds].length = marker_vcn - drl[ds].vcn;
                         /* Finally add the ENOENT terminator. */
                         ds++;
-                        if (!slots) {
-                                /* FIXME/TODO: We need to have the extra
-                                 * memory already! (AIA) */
-                                drl = ntfs_rl_realloc(drl, ds, ds + 1);
-                                if (!drl)
-                                        goto critical_error;
-                        }
+                        if (!slots)
+                                drl = ntfs_rl_realloc_nofail(drl, ds, ds + 1);
                         drl[ds].vcn = marker_vcn;
                         drl[ds].lcn = LCN_ENOENT;
                         drl[ds].length = (s64)0;
@@ -659,11 +696,6 @@ finished:
         ntfs_debug("Merged runlist:");
         ntfs_debug_dump_runlist(drl);
         return drl;
-
-critical_error:
-        /* Critical error! We cannot afford to fail here. */
-        ntfs_error(NULL, "Critical error! Not enough memory.");
-        panic("NTFS: Cannot continue.");
 }
 
 /**