Btrfs: RAID5 and RAID6
This builds on David Woodhouse's original Btrfs raid5/6 implementation.
The code has changed quite a bit, blame Chris Mason for any bugs.
Read/modify/write is done after the higher levels of the filesystem have
prepared a given bio. This means the higher layers are not responsible
for building full stripes, and they don't need to query for the topology
of the extents that may get allocated during delayed allocation runs.
It also means different files can easily share the same stripe.
But, it does expose us to incorrect parity if we crash or lose power
while doing a read/modify/write cycle. This will be addressed in a
later commit.
Scrub is unable to repair crc errors on raid5/6 chunks.
Discard does not work on raid5/6 (yet)
The stripe size is fixed at 64KiB per disk. This will be tunable
in a later commit.
Signed-off-by: Chris Mason <chris.mason@fusionio.com>
diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index 59ea2e4..62020b7 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -1463,10 +1463,14 @@
}
static struct btrfs_free_space *
-find_free_space(struct btrfs_free_space_ctl *ctl, u64 *offset, u64 *bytes)
+find_free_space(struct btrfs_free_space_ctl *ctl, u64 *offset, u64 *bytes,
+ unsigned long align)
{
struct btrfs_free_space *entry;
struct rb_node *node;
+ u64 ctl_off;
+ u64 tmp;
+ u64 align_off;
int ret;
if (!ctl->free_space_offset.rb_node)
@@ -1481,15 +1485,34 @@
if (entry->bytes < *bytes)
continue;
+ /* make sure the space returned is big enough
+ * to match our requested alignment
+ */
+ if (*bytes >= align) {
+ ctl_off = entry->offset - ctl->start;
+ tmp = ctl_off + align - 1;;
+ do_div(tmp, align);
+ tmp = tmp * align + ctl->start;
+ align_off = tmp - entry->offset;
+ } else {
+ align_off = 0;
+ tmp = entry->offset;
+ }
+
+ if (entry->bytes < *bytes + align_off)
+ continue;
+
if (entry->bitmap) {
- ret = search_bitmap(ctl, entry, offset, bytes);
- if (!ret)
+ ret = search_bitmap(ctl, entry, &tmp, bytes);
+ if (!ret) {
+ *offset = tmp;
return entry;
+ }
continue;
}
- *offset = entry->offset;
- *bytes = entry->bytes;
+ *offset = tmp;
+ *bytes = entry->bytes - align_off;
return entry;
}
@@ -2091,9 +2114,12 @@
struct btrfs_free_space *entry = NULL;
u64 bytes_search = bytes + empty_size;
u64 ret = 0;
+ u64 align_gap = 0;
+ u64 align_gap_len = 0;
spin_lock(&ctl->tree_lock);
- entry = find_free_space(ctl, &offset, &bytes_search);
+ entry = find_free_space(ctl, &offset, &bytes_search,
+ block_group->full_stripe_len);
if (!entry)
goto out;
@@ -2103,9 +2129,15 @@
if (!entry->bytes)
free_bitmap(ctl, entry);
} else {
+
unlink_free_space(ctl, entry);
- entry->offset += bytes;
- entry->bytes -= bytes;
+ align_gap_len = offset - entry->offset;
+ align_gap = entry->offset;
+
+ entry->offset = offset + bytes;
+ WARN_ON(entry->bytes < bytes + align_gap_len);
+
+ entry->bytes -= bytes + align_gap_len;
if (!entry->bytes)
kmem_cache_free(btrfs_free_space_cachep, entry);
else
@@ -2115,6 +2147,8 @@
out:
spin_unlock(&ctl->tree_lock);
+ if (align_gap_len)
+ __btrfs_add_free_space(ctl, align_gap, align_gap_len);
return ret;
}