Btrfs: fix max chunk size on raid5/6

[deliverable/linux.git] / fs / btrfs / volumes.c

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 5d6010ba8b7eb3fc5121fc5e29a738c175c45865..538c5cfa005f161b45eaebf1e32c16788f5781de 100644 (file)
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -3837,10 +3837,6 @@ static int __btrfs_alloc_chunk(struct btrfs_trans_handle *trans,
         */
        data_stripes = num_stripes / ncopies;
 
-       if (stripe_size * ndevs > max_chunk_size * ncopies) {
-               stripe_size = max_chunk_size * ncopies;
-               do_div(stripe_size, ndevs);
-       }
        if (type & BTRFS_BLOCK_GROUP_RAID5) {
                raid_stripe_len = find_raid56_stripe_len(ndevs - 1,
                                 btrfs_super_stripesize(info->super_copy));
@@ -3851,6 +3847,27 @@ static int __btrfs_alloc_chunk(struct btrfs_trans_handle *trans,
                                 btrfs_super_stripesize(info->super_copy));
                data_stripes = num_stripes - 2;
        }
+
+       /*
+        * Use the number of data stripes to figure out how big this chunk
+        * is really going to be in terms of logical address space,
+        * and compare that answer with the max chunk size
+        */
+       if (stripe_size * data_stripes > max_chunk_size) {
+               u64 mask = (1ULL << 24) - 1;
+               stripe_size = max_chunk_size;
+               do_div(stripe_size, data_stripes);
+
+               /* bump the answer up to a 16MB boundary */
+               stripe_size = (stripe_size + mask) & ~mask;
+
+               /* but don't go higher than the limits we found
+                * while searching for free extents
+                */
+               if (stripe_size > devices_info[ndevs-1].max_avail)
+                       stripe_size = devices_info[ndevs-1].max_avail;
+       }
+
        do_div(stripe_size, dev_stripes);
 
        /* align to BTRFS_STRIPE_LEN */