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btrfs: Fix threshold calculation for block groups smaller than 1GB

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If a block group is smaller than 1GB, the extent entry threadhold
calculation will always set the threshold to 0.

So as free space gets fragmented, btrfs will switch to use bitmap
to manage free space, but then will never switch back to extents
due to this bug.

Reviewed-by: Josef Bacik <josef@redhat.com>
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
This commit is contained in:
Li Zefan 2010-11-09 14:48:01 +08:00
parent 65e5341b9a
commit 8eb2d829ff
1 changed files with 6 additions and 2 deletions
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8
fs/btrfs/free-space-cache.c
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@ -1016,14 +1016,18 @@ static void recalculate_thresholds(struct btrfs_block_group_cache *block_group)
u64 max_bytes;
u64 bitmap_bytes;
u64 extent_bytes;
u64 size = block_group->key.offset;
/*
* The goal is to keep the total amount of memory used per 1gb of space
* at or below 32k, so we need to adjust how much memory we allow to be
* used by extent based free space tracking
*/
max_bytes = MAX_CACHE_BYTES_PER_GIG *
(div64_u64(block_group->key.offset, 1024 * 1024 * 1024));
if (size < 1024 * 1024 * 1024)
max_bytes = MAX_CACHE_BYTES_PER_GIG;
else
max_bytes = MAX_CACHE_BYTES_PER_GIG *
div64_u64(size, 1024 * 1024 * 1024);
/*
* we want to account for 1 more bitmap than what we have so we can make