1 files changed, 97 insertions, 34 deletions

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 5e17d5f22a7e..a27129065144 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4354,56 +4354,119 @@ int ext4_getattr(struct vfsmount *mnt, struct dentry *dentry,
         return 0;
 }
 
+static int ext4_indirect_trans_blocks(struct inode *inode, int nrblocks,
+                                      int chunk)
+{
+        int indirects;
+
+        /* if nrblocks are contiguous */
+        if (chunk) {
+                /*
+                 * With N contiguous data blocks, it need at most
+                 * N/EXT4_ADDR_PER_BLOCK(inode->i_sb) indirect blocks
+                 * 2 dindirect blocks
+                 * 1 tindirect block
+                 */
+                indirects = nrblocks / EXT4_ADDR_PER_BLOCK(inode->i_sb);
+                return indirects + 3;
+        }
+        /*
+         * if nrblocks are not contiguous, worse case, each block touch
+         * a indirect block, and each indirect block touch a double indirect
+         * block, plus a triple indirect block
+         */
+        indirects = nrblocks * 2 + 1;
+        return indirects;
+}
+
+static int ext4_index_trans_blocks(struct inode *inode, int nrblocks, int chunk)
+{
+        if (!(EXT4_I(inode)->i_flags & EXT4_EXTENTS_FL))
+                return ext4_indirect_trans_blocks(inode, nrblocks, 0);
+        return ext4_ext_index_trans_blocks(inode, nrblocks, 0);
+}
 /*
- * How many blocks doth make a writepage()?
+ * Account for index blocks, block groups bitmaps and block group
+ * descriptor blocks if modify datablocks and index blocks
+ * worse case, the indexs blocks spread over different block groups
  *
- * With N blocks per page, it may be:
- * N data blocks
- * 2 indirect block
- * 2 dindirect
- * 1 tindirect
- * N+5 bitmap blocks (from the above)
- * N+5 group descriptor summary blocks
- * 1 inode block
- * 1 superblock.
- * 2 * EXT4_SINGLEDATA_TRANS_BLOCKS for the quote files
+ * If datablocks are discontiguous, they are possible to spread over
+ * different block groups too. If they are contiugous, with flexbg,
+ * they could still across block group boundary.
  *
- * 3 * (N + 5) + 2 + 2 * EXT4_SINGLEDATA_TRANS_BLOCKS
+ * Also account for superblock, inode, quota and xattr blocks
+ */
+int ext4_meta_trans_blocks(struct inode *inode, int nrblocks, int chunk)
+{
+        int groups, gdpblocks;
+        int idxblocks;
+        int ret = 0;
+
+        /*
+         * How many index blocks need to touch to modify nrblocks?
+         * The "Chunk" flag indicating whether the nrblocks is
+         * physically contiguous on disk
+         *
+         * For Direct IO and fallocate, they calls get_block to allocate
+         * one single extent at a time, so they could set the "Chunk" flag
+         */
+        idxblocks = ext4_index_trans_blocks(inode, nrblocks, chunk);
+
+        ret = idxblocks;
+
+        /*
+         * Now let's see how many group bitmaps and group descriptors need
+         * to account
+         */
+        groups = idxblocks;
+        if (chunk)
+                groups += 1;
+        else
+                groups += nrblocks;
+
+        gdpblocks = groups;
+        if (groups > EXT4_SB(inode->i_sb)->s_groups_count)
+                groups = EXT4_SB(inode->i_sb)->s_groups_count;
+        if (groups > EXT4_SB(inode->i_sb)->s_gdb_count)
+                gdpblocks = EXT4_SB(inode->i_sb)->s_gdb_count;
+
+        /* bitmaps and block group descriptor blocks */
+        ret += groups + gdpblocks;
+
+        /* Blocks for super block, inode, quota and xattr blocks */
+        ret += EXT4_META_TRANS_BLOCKS(inode->i_sb);
+
+        return ret;
+}
+
+/*
+ * Calulate the total number of credits to reserve to fit
+ * the modification of a single pages into a single transaction
  *
- * With ordered or writeback data it's the same, less the N data blocks.
+ * This could be called via ext4_write_begin() or later
+ * ext4_da_writepages() in delalyed allocation case.
  *
- * If the inode's direct blocks can hold an integral number of pages then a
- * page cannot straddle two indirect blocks, and we can only touch one indirect
- * and dindirect block, and the "5" above becomes "3".
+ * In both case it's possible that we could allocating multiple
+ * chunks of blocks. We need to consider the worse case, when
+ * one new block per extent.
  *
- * This still overestimates under most circumstances.  If we were to pass the
- * start and end offsets in here as well we could do block_to_path() on each
- * block and work out the exact number of indirects which are touched.  Pah.
+ * For Direct IO and fallocate, the journal credits reservation
+ * is based on one single extent allocation, so they could use
+ * EXT4_DATA_TRANS_BLOCKS to get the needed credit to log a single
+ * chunk of allocation needs.
  */
-
 int ext4_writepage_trans_blocks(struct inode *inode)
 {
         int bpp = ext4_journal_blocks_per_page(inode);
-        int indirects = (EXT4_NDIR_BLOCKS % bpp) ? 5 : 3;
         int ret;
 
-        if (EXT4_I(inode)->i_flags & EXT4_EXTENTS_FL)
-                return ext4_ext_writepage_trans_blocks(inode, bpp);
+        ret = ext4_meta_trans_blocks(inode, bpp, 0);
 
+        /* Account for data blocks for journalled mode */
         if (ext4_should_journal_data(inode))
-                ret = 3 * (bpp + indirects) + 2;
-        else
-                ret = 2 * (bpp + indirects) + 2;
-
-#ifdef CONFIG_QUOTA
-        /* We know that structure was already allocated during DQUOT_INIT so
-         * we will be updating only the data blocks + inodes */
-        ret += 2*EXT4_QUOTA_TRANS_BLOCKS(inode->i_sb);
-#endif
-
+                ret += bpp;
         return ret;
 }
-
 /*
  * The caller must have previously called ext4_reserve_inode_write().
  * Give this, we know that the caller already has write access to iloc->bh.