gfs2: Turn trunc_dealloc into punch_hole

Add an upper bound to the range of blocks to deallocate blocks to
function trunc_dealloc so that this function can be used for truncating
a file as well as for punching a hole into a file.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Bob Peterson <rpeterso@redhat.com>

1 files changed, 120 insertions, 59 deletions

diff --git a/fs/gfs2/bmap.c b/fs/gfs2/bmap.c
index 8fd42ae026dd..f6dbd2f400cc 100644
--- a/fs/gfs2/bmap.c
+++ b/fs/gfs2/bmap.c
@@ -461,13 +461,6 @@ enum alloc_state {
         /* ALLOC_UNSTUFF = 3,   TBD and rather complicated */
 };
 
-static inline unsigned int hptrs(struct gfs2_sbd *sdp, const unsigned int hgt)
-{
-        if (hgt)
-                return sdp->sd_inptrs;
-        return sdp->sd_diptrs;
-}
-
 /**
  * gfs2_bmap_alloc - Build a metadata tree of the requested height
  * @inode: The GFS2 inode
@@ -1243,38 +1236,48 @@ out:
         return ret;
 }
 
+static bool mp_eq_to_hgt(struct metapath *mp, __u16 *list, unsigned int h)
+{
+        if (memcmp(mp->mp_list, list, h * sizeof(mp->mp_list[0])))
+                return false;
+        return true;
+}
+
 /**
  * find_nonnull_ptr - find a non-null pointer given a metapath and height
- * assumes the metapath is valid (with buffers) out to height h
  * @mp: starting metapath
  * @h: desired height to search
  *
+ * Assumes the metapath is valid (with buffers) out to height h.
  * Returns: true if a non-null pointer was found in the metapath buffer
  *          false if all remaining pointers are NULL in the buffer
  */
 static bool find_nonnull_ptr(struct gfs2_sbd *sdp, struct metapath *mp,
-                             unsigned int h)
+                             unsigned int h,
+                             __u16 *end_list, unsigned int end_aligned)
 {
-        __be64 *ptr;
-        unsigned int ptrs = hptrs(sdp, h) - 1;
+        struct buffer_head *bh = mp->mp_bh[h];
+        __be64 *first, *ptr, *end;
+
+        first = metaptr1(h, mp);
+        ptr = first + mp->mp_list[h];
+        end = (__be64 *)(bh->b_data + bh->b_size);
+        if (end_list && mp_eq_to_hgt(mp, end_list, h)) {
+                bool keep_end = h < end_aligned;
+                end = first + end_list[h] + keep_end;
+        }
 
-        while (true) {
-                ptr = metapointer(h, mp);
+        while (ptr < end) {
                 if (*ptr) { /* if we have a non-null pointer */
-                        /* Now zero the metapath after the current height. */
+                        mp->mp_list[h] = ptr - first;
                         h++;
                         if (h < GFS2_MAX_META_HEIGHT)
-                                memset(&mp->mp_list[h], 0,
-                                       (GFS2_MAX_META_HEIGHT - h) *
-                                       sizeof(mp->mp_list[0]));
+                                mp->mp_list[h] = 0;
                         return true;
                 }
-
-                if (mp->mp_list[h] < ptrs)
-                        mp->mp_list[h]++;
-                else
-                        return false; /* no more pointers in this buffer */
+                ptr++;
         }
+        return false;
 }
 
 enum dealloc_states {
@@ -1284,16 +1287,10 @@ enum dealloc_states {
         DEALLOC_DONE = 3,       /* process complete */
 };
 
-static bool mp_eq_to_hgt(struct metapath *mp, __u16 *list, unsigned int h)
-{
-        if (memcmp(mp->mp_list, list, h * sizeof(mp->mp_list[0])))
-                return false;
-        return true;
-}
-
 static inline void
 metapointer_range(struct metapath *mp, int height,
                   __u16 *start_list, unsigned int start_aligned,
+                  __u16 *end_list, unsigned int end_aligned,
                   __be64 **start, __be64 **end)
 {
         struct buffer_head *bh = mp->mp_bh[height];
@@ -1306,29 +1303,55 @@ metapointer_range(struct metapath *mp, int height,
                 *start = first + start_list[height] + keep_start;
         }
         *end = (__be64 *)(bh->b_data + bh->b_size);
+        if (end_list && mp_eq_to_hgt(mp, end_list, height)) {
+                bool keep_end = height < end_aligned;
+                *end = first + end_list[height] + keep_end;
+        }
+}
+
+static inline bool walk_done(struct gfs2_sbd *sdp,
+                             struct metapath *mp, int height,
+                             __u16 *end_list, unsigned int end_aligned)
+{
+        __u16 end;
+
+        if (end_list) {
+                bool keep_end = height < end_aligned;
+                if (!mp_eq_to_hgt(mp, end_list, height))
+                        return false;
+                end = end_list[height] + keep_end;
+        } else
+                end = (height > 0) ? sdp->sd_inptrs : sdp->sd_diptrs;
+        return mp->mp_list[height] >= end;
 }
 
 /**
- * trunc_dealloc - truncate a file down to a desired size
+ * punch_hole - deallocate blocks in a file
  * @ip: inode to truncate
- * @newsize: The desired size of the file
+ * @offset: the start of the hole
+ * @length: the size of the hole (or 0 for truncate)
+ *
+ * Punch a hole into a file or truncate a file at a given position.  This
+ * function operates in whole blocks (@offset and @length are rounded
+ * accordingly); partially filled blocks must be cleared otherwise.
  *
- * This function truncates a file to newsize. It works from the
- * bottom up, and from the right to the left. In other words, it strips off
- * the highest layer (data) before stripping any of the metadata. Doing it
- * this way is best in case the operation is interrupted by power failure, etc.
- * The dinode is rewritten in every transaction to guarantee integrity.
+ * This function works from the bottom up, and from the right to the left. In
+ * other words, it strips off the highest layer (data) before stripping any of
+ * the metadata. Doing it this way is best in case the operation is interrupted
+ * by power failure, etc.  The dinode is rewritten in every transaction to
+ * guarantee integrity.
  */
-static int trunc_dealloc(struct gfs2_inode *ip, u64 newsize)
+static int punch_hole(struct gfs2_inode *ip, u64 offset, u64 length)
 {
         struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
-        struct metapath mp;
+        struct metapath mp = {};
         struct buffer_head *dibh, *bh;
         struct gfs2_holder rd_gh;
         unsigned int bsize_shift = sdp->sd_sb.sb_bsize_shift;
-        u64 lblock = (newsize + (1 << bsize_shift) - 1) >> bsize_shift;
-        __u16 start_list[GFS2_MAX_META_HEIGHT]; /* new beginning of truncation */
-        unsigned int start_aligned;
+        u64 lblock = (offset + (1 << bsize_shift) - 1) >> bsize_shift;
+        __u16 start_list[GFS2_MAX_META_HEIGHT];
+        __u16 __end_list[GFS2_MAX_META_HEIGHT], *end_list = NULL;
+        unsigned int start_aligned, end_aligned;
         unsigned int strip_h = ip->i_height - 1;
         u32 btotal = 0;
         int ret, state;
@@ -1336,19 +1359,49 @@ static int trunc_dealloc(struct gfs2_inode *ip, u64 newsize)
         u64 prev_bnr = 0;
         __be64 *start, *end;
 
-        memset(&mp, 0, sizeof(mp));
-        find_metapath(sdp, lblock, &mp, ip->i_height);
+        /*
+         * The start position of the hole is defined by lblock, start_list, and
+         * start_aligned.  The end position of the hole is defined by lend,
+         * end_list, and end_aligned.
+         *
+         * start_aligned and end_aligned define down to which height the start
+         * and end positions are aligned to the metadata tree (i.e., the
+         * position is a multiple of the metadata granularity at the height
+         * above).  This determines at which heights additional meta pointers
+         * needs to be preserved for the remaining data.
+         */
+
+        if (length) {
+                u64 maxsize = sdp->sd_heightsize[ip->i_height];
+                u64 end_offset = offset + length;
+                u64 lend;
+
+                /*
+                 * Clip the end at the maximum file size for the given height:
+                 * that's how far the metadata goes; files bigger than that
+                 * will have additional layers of indirection.
+                 */
+                if (end_offset > maxsize)
+                        end_offset = maxsize;
+                lend = end_offset >> bsize_shift;
+
+                if (lblock >= lend)
+                        return 0;
 
+                find_metapath(sdp, lend, &mp, ip->i_height);
+                end_list = __end_list;
+                memcpy(end_list, mp.mp_list, sizeof(mp.mp_list));
+
+                for (mp_h = ip->i_height - 1; mp_h > 0; mp_h--) {
+                        if (end_list[mp_h])
+                                break;
+                }
+                end_aligned = mp_h;
+        }
+
+        find_metapath(sdp, lblock, &mp, ip->i_height);
         memcpy(start_list, mp.mp_list, sizeof(start_list));
 
-        /*
-         * Set start_aligned to the metadata height up to which the truncate
-         * point is aligned to the metadata tree (i.e., the truncate point is a
-         * multiple of the granularity at the height above).  This determines
-         * at which heights an additional meta pointer needs to be preserved:
-         * an additional meta pointer is needed at a given height if
-         * height < start_aligned.
-         */
         for (mp_h = ip->i_height - 1; mp_h > 0; mp_h--) {
                 if (start_list[mp_h])
                         break;
@@ -1367,7 +1420,7 @@ static int trunc_dealloc(struct gfs2_inode *ip, u64 newsize)
         /* issue read-ahead on metadata */
         for (mp_h = 0; mp_h < mp.mp_aheight - 1; mp_h++) {
                 metapointer_range(&mp, mp_h, start_list, start_aligned,
-                                  &start, &end);
+                                  end_list, end_aligned, &start, &end);
                 gfs2_metapath_ra(ip->i_gl, start, end);
         }
 
@@ -1411,7 +1464,14 @@ static int trunc_dealloc(struct gfs2_inode *ip, u64 newsize)
                                 goto out;
                         }
 
+                        /*
+                         * Below, passing end_aligned as 0 gives us the
+                         * metapointer range excluding the end point: the end
+                         * point is the first metapath we must not deallocate!
+                         */
+
                         metapointer_range(&mp, mp_h, start_list, start_aligned,
+                                          end_list, 0 /* end_aligned */,
                                           &start, &end);
                         ret = sweep_bh_for_rgrps(ip, &rd_gh, mp.mp_bh[mp_h],
                                                  start, end,
@@ -1448,13 +1508,13 @@ static int trunc_dealloc(struct gfs2_inode *ip, u64 newsize)
                         }
                         mp.mp_list[mp_h] = 0;
                         mp_h--; /* search one metadata height down */
-                        if (mp.mp_list[mp_h] >= hptrs(sdp, mp_h) - 1)
-                                break; /* loop around in the same state */
                         mp.mp_list[mp_h]++;
+                        if (walk_done(sdp, &mp, mp_h, end_list, end_aligned))
+                                break;
                         /* Here we've found a part of the metapath that is not
                          * allocated. We need to search at that height for the
                          * next non-null pointer. */
-                        if (find_nonnull_ptr(sdp, &mp, mp_h)) {
+                        if (find_nonnull_ptr(sdp, &mp, mp_h, end_list, end_aligned)) {
                                 state = DEALLOC_FILL_MP;
                                 mp_h++;
                         }
@@ -1474,6 +1534,7 @@ static int trunc_dealloc(struct gfs2_inode *ip, u64 newsize)
                                 for (; ret > 1; ret--) {
                                         metapointer_range(&mp, mp.mp_aheight - ret,
                                                           start_list, start_aligned,
+                                                          end_list, end_aligned,
                                                           &start, &end);
                                         gfs2_metapath_ra(ip->i_gl, start, end);
                                 }
@@ -1490,7 +1551,7 @@ static int trunc_dealloc(struct gfs2_inode *ip, u64 newsize)
                         /* If we find a non-null block pointer, crawl a bit
                            higher up in the metapath and try again, otherwise
                            we need to look lower for a new starting point. */
-                        if (find_nonnull_ptr(sdp, &mp, mp_h))
+                        if (find_nonnull_ptr(sdp, &mp, mp_h, end_list, end_aligned))
                                 mp_h++;
                         else
                                 state = DEALLOC_MP_LOWER;
@@ -1587,7 +1648,7 @@ static int do_shrink(struct inode *inode, u64 newsize)
         if (gfs2_is_stuffed(ip))
                 return 0;
 
-        error = trunc_dealloc(ip, newsize);
+        error = punch_hole(ip, newsize, 0);
         if (error == 0)
                 error = trunc_end(ip);
 
@@ -1719,7 +1780,7 @@ out:
 int gfs2_truncatei_resume(struct gfs2_inode *ip)
 {
         int error;
-        error = trunc_dealloc(ip, i_size_read(&ip->i_inode));
+        error = punch_hole(ip, i_size_read(&ip->i_inode), 0);
         if (!error)
                 error = trunc_end(ip);
         return error;
@@ -1727,7 +1788,7 @@ int gfs2_truncatei_resume(struct gfs2_inode *ip)
 
 int gfs2_file_dealloc(struct gfs2_inode *ip)
 {
-        return trunc_dealloc(ip, 0);
+        return punch_hole(ip, 0, 0);
 }
 
 /**