* [PATCH] Btrfs: don't allocate more than max_available bytes when looped
@ 2009-08-02 22:24 Giuseppe Scrivano
2009-08-03 20:53 ` Giuseppe Scrivano
0 siblings, 1 reply; 2+ messages in thread
From: Giuseppe Scrivano @ 2009-08-02 22:24 UTC (permalink / raw)
To: linux-btrfs
Hello,
I had a problem running this simple test case that I was writing to test
the GNU coreutils cp tool:
truncate --size=256M btrfs.img
mkfs.btrfs btrfs.img
mkdir btrfs
mount -t btrfs -o loop btrfs.img btrfs
dd bs=1M count=200 if=/dev/zero of=btrfs/alloc.test
with the current git version I get an ENOSPC error on dd, even if the
available space is 256M.
The simple patch that I have attached seems to fix it.
Am I missing someting? If there is something wrong please let me know
and I'll try to fix it.
Regards,
Giuseppe
>From d6345f720f9fa5e60edd904d90d56bf9e96fb118 Mon Sep 17 00:00:00 2001
From: Giuseppe Scrivano <gscrivano@gnu.org>
Date: Sun, 2 Aug 2009 23:29:21 +0200
Subject: [PATCH] Btrfs: don't allocate more than max_available bytes when looped
avoid that __btrfs_alloc_chunk can try to allocate more than
max_available bytes if it wasn't possible on the first attempt.
---
fs/btrfs/volumes.c | 13 ++++++++-----
1 files changed, 8 insertions(+), 5 deletions(-)
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 5dbefd1..38d93f6 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -2180,8 +2180,8 @@ static int __btrfs_alloc_chunk(struct btrfs_trans_handle *trans,
max_chunk_size = min(div_factor(fs_devices->total_rw_bytes, 1),
max_chunk_size);
-again:
max_avail = 0;
+again:
if (!map || map->num_stripes != num_stripes) {
kfree(map);
map = kmalloc(map_lookup_size(num_stripes), GFP_NOFS);
@@ -2196,11 +2196,12 @@ again:
do_div(calc_size, stripe_len);
calc_size *= stripe_len;
}
- /* we don't want tiny stripes */
- calc_size = max_t(u64, min_stripe_size, calc_size);
- do_div(calc_size, stripe_len);
- calc_size *= stripe_len;
+ /* we don't want tiny stripes */
+ calc_size = max_t(u64, min_stripe_size, calc_size);
+
+ do_div(calc_size, stripe_len);
+ calc_size *= stripe_len;
cur = fs_devices->alloc_list.next;
index = 0;
@@ -2217,6 +2218,8 @@ again:
*/
if (!looped)
min_free += 1024 * 1024;
+ else
+ min_free = min_t(u64, max_avail, min_free);
INIT_LIST_HEAD(&private_devs);
while (index < num_stripes) {
--
1.6.3.3
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] Btrfs: don't allocate more than max_available bytes when looped
2009-08-02 22:24 [PATCH] Btrfs: don't allocate more than max_available bytes when looped Giuseppe Scrivano
@ 2009-08-03 20:53 ` Giuseppe Scrivano
0 siblings, 0 replies; 2+ messages in thread
From: Giuseppe Scrivano @ 2009-08-03 20:53 UTC (permalink / raw)
To: linux-btrfs, Chris Mason
Hi Chris,
Thanks for your comments, I changed the patch according to them.
>From my tests, I can see that it helps to get 10% more usable space on a
256MB partition and 5% on a 750MB one.
Cheers,
Giuseppe
>From 4eff62a7132018f8685cdeff3aa439089c708258 Mon Sep 17 00:00:00 2001
From: Giuseppe Scrivano <gscrivano@gnu.org>
Date: Mon, 3 Aug 2009 22:26:43 +0200
Subject: [PATCH] Btrfs: reduce the default min_stripe_size
The default min_stripe_size used by __btrfs_alloc_chunk was reduced to
32MB for data and 16MB for metadata chunks.
Also, after a failed attempt to alloc data, try again reducing the
minimum size by a factor of 4. It may help allocating space that
wouldn't otherwise.
---
fs/btrfs/volumes.c | 7 +++++--
1 files changed, 5 insertions(+), 2 deletions(-)
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 5dbefd1..a39b651 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -2166,10 +2166,10 @@ static int __btrfs_alloc_chunk(struct btrfs_trans_handle *trans,
if (type & BTRFS_BLOCK_GROUP_DATA) {
max_chunk_size = 10 * calc_size;
- min_stripe_size = 64 * 1024 * 1024;
+ min_stripe_size = 32 * 1024 * 1024;
} else if (type & BTRFS_BLOCK_GROUP_METADATA) {
max_chunk_size = 4 * calc_size;
- min_stripe_size = 32 * 1024 * 1024;
+ min_stripe_size = 16 * 1024 * 1024;
} else if (type & BTRFS_BLOCK_GROUP_SYSTEM) {
calc_size = 8 * 1024 * 1024;
max_chunk_size = calc_size * 2;
@@ -2190,6 +2190,9 @@ again:
map->num_stripes = num_stripes;
}
+ if (looped)
+ min_stripe_size = min_stripe_size / 4;
+
if (calc_size * num_stripes > max_chunk_size) {
calc_size = max_chunk_size;
do_div(calc_size, num_stripes);
--
1.6.3.3
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