gfs2: Fix gfs2_testbit to use clone bitmaps

Function gfs2_testbit is called in three places. Two of those places,
gfs2_alloc_extent and gfs2_unaligned_extlen, should be using the clone
bitmaps, not the "real" bitmaps. Function gfs2_unaligned_extlen is used
by the block reservations scheme to determine the length of an extent of
free blocks. Before this patch, it wasn't using the clone bitmap, which
means recently-freed blocks were treated as free blocks for the purposes
of an allocation.

This patch adds a new parameter to gfs2_testbit to indicate whether or
not the clone bitmaps should be used (if available).

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

2 files changed, 40 insertions, 25 deletions

diff --git a/fs/gfs2/incore.h b/fs/gfs2/incore.h
index b50908211b69..b96d39c28e17 100644
--- a/fs/gfs2/incore.h
+++ b/fs/gfs2/incore.h
@@ -65,6 +65,27 @@ struct gfs2_log_operations {
 
 #define GBF_FULL 1
 
+/**
+ * Clone bitmaps (bi_clone):
+ *
+ * - When a block is freed, we remember the previous state of the block in the
+ *   clone bitmap, and only mark the block as free in the real bitmap.
+ *
+ * - When looking for a block to allocate, we check for a free block in the
+ *   clone bitmap, and if no clone bitmap exists, in the real bitmap.
+ *
+ * - For allocating a block, we mark it as allocated in the real bitmap, and if
+ *   a clone bitmap exists, also in the clone bitmap.
+ *
+ * - At the end of a log_flush, we copy the real bitmap into the clone bitmap
+ *   to make the clone bitmap reflect the current allocation state.
+ *   (Alternatively, we could remove the clone bitmap.)
+ *
+ * The clone bitmaps are in-core only, and is never written to disk.
+ *
+ * These steps ensure that blocks which have been freed in a transaction cannot
+ * be reallocated in that same transaction.
+ */
 struct gfs2_bitmap {
         struct buffer_head *bi_bh;
         char *bi_clone;
diff --git a/fs/gfs2/rgrp.c b/fs/gfs2/rgrp.c
index 7c5afeba8888..ef50fe9b880a 100644
--- a/fs/gfs2/rgrp.c
+++ b/fs/gfs2/rgrp.c
@@ -123,17 +123,26 @@ static inline void gfs2_setbit(const struct gfs2_rbm *rbm, bool do_clone,
 /**
  * gfs2_testbit - test a bit in the bitmaps
  * @rbm: The bit to test
+ * @use_clone: If true, test the clone bitmap, not the official bitmap.
+ *
+ * Some callers like gfs2_unaligned_extlen need to test the clone bitmaps,
+ * not the "real" bitmaps, to avoid allocating recently freed blocks.
  *
  * Returns: The two bit block state of the requested bit
  */
 
-static inline u8 gfs2_testbit(const struct gfs2_rbm *rbm)
+static inline u8 gfs2_testbit(const struct gfs2_rbm *rbm, bool use_clone)
 {
         struct gfs2_bitmap *bi = rbm_bi(rbm);
-        const u8 *buffer = bi->bi_bh->b_data + bi->bi_offset;
+        const u8 *buffer;
         const u8 *byte;
         unsigned int bit;
 
+        if (use_clone && bi->bi_clone)
+                buffer = bi->bi_clone;
+        else
+                buffer = bi->bi_bh->b_data;
+        buffer += bi->bi_offset;
         byte = buffer + (rbm->offset / GFS2_NBBY);
         bit = (rbm->offset % GFS2_NBBY) * GFS2_BIT_SIZE;
 
@@ -322,7 +331,7 @@ static bool gfs2_unaligned_extlen(struct gfs2_rbm *rbm, u32 n_unaligned, u32 *le
         u8 res;
 
         for (n = 0; n < n_unaligned; n++) {
-                res = gfs2_testbit(rbm);
+                res = gfs2_testbit(rbm, true);
                 if (res != GFS2_BLKST_FREE)
                         return true;
                 (*len)--;
@@ -2147,26 +2156,6 @@ void gfs2_inplace_release(struct gfs2_inode *ip)
 }
 
 /**
- * gfs2_get_block_type - Check a block in a RG is of given type
- * @rgd: the resource group holding the block
- * @block: the block number
- *
- * Returns: The block type (GFS2_BLKST_*)
- */
-
-static unsigned char gfs2_get_block_type(struct gfs2_rgrpd *rgd, u64 block)
-{
-        struct gfs2_rbm rbm = { .rgd = rgd, };
-        int ret;
-
-        ret = gfs2_rbm_from_block(&rbm, block);
-        WARN_ON_ONCE(ret != 0);
-
-        return gfs2_testbit(&rbm);
-}
-
-
-/**
  * gfs2_alloc_extent - allocate an extent from a given bitmap
  * @rbm: the resource group information
  * @dinode: TRUE if the first block we allocate is for a dinode
@@ -2190,7 +2179,7 @@ static void gfs2_alloc_extent(const struct gfs2_rbm *rbm, bool dinode,
         block++;
         while (*n < elen) {
                 ret = gfs2_rbm_from_block(&pos, block);
-                if (ret || gfs2_testbit(&pos) != GFS2_BLKST_FREE)
+                if (ret || gfs2_testbit(&pos, true) != GFS2_BLKST_FREE)
                         break;
                 gfs2_trans_add_meta(pos.rgd->rd_gl, rbm_bi(&pos)->bi_bh);
                 gfs2_setbit(&pos, true, GFS2_BLKST_USED);
@@ -2543,6 +2532,7 @@ int gfs2_check_blk_type(struct gfs2_sbd *sdp, u64 no_addr, unsigned int type)
 {
         struct gfs2_rgrpd *rgd;
         struct gfs2_holder rgd_gh;
+        struct gfs2_rbm rbm;
         int error = -EINVAL;
 
         rgd = gfs2_blk2rgrpd(sdp, no_addr, 1);
@@ -2553,7 +2543,11 @@ int gfs2_check_blk_type(struct gfs2_sbd *sdp, u64 no_addr, unsigned int type)
         if (error)
                 goto fail;
 
-        if (gfs2_get_block_type(rgd, no_addr) != type)
+        rbm.rgd = rgd;
+        error = gfs2_rbm_from_block(&rbm, no_addr);
+        WARN_ON_ONCE(error != 0);
+
+        if (gfs2_testbit(&rbm, false) != type)
                 error = -ESTALE;
 
         gfs2_glock_dq_uninit(&rgd_gh);