Original __btrfs_alloc_chunk() use max_chunk_size to limit chunk size,
however it mixed the on-disk space with logical space.
When comes to 10% of writable space, max_chunk_size is used with on-disk
size, but it is also used as logical space size limit, so it is very
confusing and causing inconsistence in different profile.
For example:
on M single, D single 5G btrfs single device,
data chunk is limited to 512M due to 10% limit.
on M RAID1, D RAID1 10Gx2 btrfs 2 devices,
data chunk is limited to 2G due to 10% limit is mixed with on-disk
space, causing the logical chunk space to 1G, twice than single device.
This patch will make the logical and on-disk space limit independent and
clear and solve the above inconsistence.
Signed-off-by: Qu Wenruo <quwen...@cn.fujitsu.com>
---
changelog:
v2:
Newly introduced.
---
fs/btrfs/volumes.c | 40 ++++++++++++++++++++++++++--------------
1 file changed, 26 insertions(+), 14 deletions(-)
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 0144790..8e74b34 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -4235,10 +4235,12 @@ static int __btrfs_alloc_chunk(struct
btrfs_trans_handle *trans,
int ncopies; /* how many copies to data has */
int ret;
u64 max_stripe_size;
- u64 max_chunk_size;
+ u64 max_logical_size; /* Up limit on chunk's logical size */
+ u64 max_physical_size; /* Up limit on a chunk's on-disk size */
u64 stripe_size;
u64 num_bytes;
u64 raid_stripe_len = BTRFS_STRIPE_LEN;
+ int need_bump = 0;
int ndevs;
int i;
int j;
@@ -4260,7 +4262,7 @@ static int __btrfs_alloc_chunk(struct btrfs_trans_handle
*trans,
if (type & BTRFS_BLOCK_GROUP_DATA) {
max_stripe_size = 1024 * 1024 * 1024;
- max_chunk_size = 10 * max_stripe_size;
+ max_logical_size = 10 * max_stripe_size;
if (!devs_max)
devs_max = BTRFS_MAX_DEVS(info->chunk_root);
} else if (type & BTRFS_BLOCK_GROUP_METADATA) {
@@ -4269,12 +4271,12 @@ static int __btrfs_alloc_chunk(struct
btrfs_trans_handle *trans,
max_stripe_size = 1024 * 1024 * 1024;
else
max_stripe_size = 256 * 1024 * 1024;
- max_chunk_size = max_stripe_size;
+ max_logical_size = max_stripe_size;
if (!devs_max)
devs_max = BTRFS_MAX_DEVS(info->chunk_root);
} else if (type & BTRFS_BLOCK_GROUP_SYSTEM) {
max_stripe_size = 32 * 1024 * 1024;
- max_chunk_size = 2 * max_stripe_size;
+ max_logical_size = 2 * max_stripe_size;
if (!devs_max)
devs_max = BTRFS_MAX_DEVS_SYS_CHUNK;
} else {
@@ -4284,8 +4286,7 @@ static int __btrfs_alloc_chunk(struct btrfs_trans_handle
*trans,
}
/* we don't want a chunk larger than 10% of writeable space */
- max_chunk_size = min(div_factor(fs_devices->total_rw_bytes, 1),
- max_chunk_size);
+ max_physical_size = div_factor(fs_devices->total_rw_bytes, 1);
devices_info = kzalloc(sizeof(*devices_info) * fs_devices->rw_devices,
GFP_NOFS);
@@ -4391,15 +4392,21 @@ static int __btrfs_alloc_chunk(struct
btrfs_trans_handle *trans,
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;
+ /* Restrict on-disk chunk size */
+ if (stripe_size * num_stripes > max_physical_size) {
+ stripe_size = max_physical_size;
+ do_div(stripe_size, num_stripes);
+ need_bump = 1;
+ }
+ /* restrict logical chunk size */
+ if (stripe_size * data_stripes > max_logical_size) {
+ stripe_size = max_logical_size;
do_div(stripe_size, data_stripes);
+ need_bump = 1;
+ }
+
+ if (need_bump) {
+ u64 mask = (1ULL << 24) - 1;
/* bump the answer up to a 16MB boundary */
stripe_size = (stripe_size + mask) & ~mask;
@@ -4411,6 +4418,11 @@ static int __btrfs_alloc_chunk(struct btrfs_trans_handle
*trans,
stripe_size = devices_info[ndevs-1].max_avail;
}
+ /*
+ * Special handle for DUP, since stripe_size is the largest free extent
+ * we found, DUP can only use half of it. Other profile's dev_stripes
+ * is always 1.
+ */
do_div(stripe_size, dev_stripes);
/* align to BTRFS_STRIPE_LEN */
--
2.2.1
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