@@ -3724,25 +3724,32 @@ static int __btrfs_alloc_chunk(struct btrfs_trans_handle *trans,
stripe_size = devices_info[ndevs-1].max_avail;
num_stripes = ndevs * dev_stripes;
- /*
- * this will have to be fixed for RAID1 and RAID10 over
- * more drives
- */
- 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));
- data_stripes = num_stripes - 1;
- }
- if (type & BTRFS_BLOCK_GROUP_RAID6) {
+ data_stripes = ndevs - 1;
+ if (stripe_size * data_stripes > max_chunk_size) {
+ stripe_size = max_chunk_size;
+ do_div(stripe_size, data_stripes);
+ }
+ } else if (type & BTRFS_BLOCK_GROUP_RAID6) {
raid_stripe_len = find_raid56_stripe_len(ndevs - 2,
btrfs_super_stripesize(info->super_copy));
- data_stripes = num_stripes - 2;
+ data_stripes = ndevs - 2;
+ if (stripe_size * data_stripes > max_chunk_size) {
+ stripe_size = max_chunk_size;
+ do_div(stripe_size, data_stripes);
+ }
+ } else { /* RAID1, RAID0, RAID10, SINGLE, SUP */
+ /*
+ * this will have to be fixed for RAID1 and RAID10 over
+ * more drives
+ */
+ data_stripes = num_stripes / ncopies;
+ if (stripe_size * ndevs > max_chunk_size * ncopies) {
+ stripe_size = max_chunk_size * ncopies;
+ do_div(stripe_size, ndevs);
+ }
}
do_div(stripe_size, dev_stripes);
Hi Chris, I am playing with the raid5/6 code, to adapt my "disk-usage" patches to the raid5/6 code. During this develop I found that the chunk allocation is strange. Looking at the code I found in volume.c the following codes: 3576 static int __btrfs_alloc_chunk(struct btrfs_trans_handle *trans, 3730 /* 3731 * this will have to be fixed for RAID1 and RAID10 over 3732 * more drives 3733 */ 3734 data_stripes = num_stripes / ncopies; 3735 3736 if (stripe_size * ndevs > max_chunk_size * ncopies) { 3737 stripe_size = max_chunk_size * ncopies; 3738 do_div(stripe_size, ndevs); 3739 } This code decides how big is a chunk, following two mains roles: 1) the chunk stripe shall be less than max_stripe_size 2) the chunk capability (the space usable by the user) shall be less than max_chunk_size. The code above works well in case of RAID0/RAID1/DUP/SINGLE/RAID10 but doesn't play well in case of RAID5/6. In fact in case the chunk type is BTRFS_BLOCK_GROUP_METADATA then max_stripe_size is 1GB and max_chunk_size is 1GB too. If the number of devices (ndevs) is 7 and the raid profile is RAID6, then ncopies is 3, the stripe_size is 1GB*3/7 = 438MB, which lead to a chunk size of 2.14GB ! Which is not the expected value. I think that we should change the test above in raid6 case to data_stripes = ndevs - 2; if (stripe_size * data_stripes > max_chunk_size) { stripe_size = max_chunk_size; do_div(stripe_size, data_stripes); } The patch below should solve this issue, and clean up a bit the logic separating the code of raid5, raid6 from the code of the others raid profiles. Anyway I would like to point out another possible issue: the fragmentation. To avoid the fragmentation should we round up the stripe size to a more sane value like like 256MB ? I know that this could led to an "insane" chunk size when the number of disk is higher; but the current logic ( the stripe_size is equal to the chunk_size / number_of_device) could lead to fragmentation problem when different raid profiles where used together. BR G.Baroncelli Signed-off-by: Goffredo Baroncelli <kreijack@inwind.it>