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Btrfs: use the global block reserve if we cannot reserve space

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We call use_block_rsv right before we make an allocation in order to make sure
we have enough space.  Now normally people have called btrfs_start_transaction()
with the appropriate amount of space that we need, so we just use some of that
pre-reserved space and move along happily.  The problem is where people use
btrfs_join_transaction(), which doesn't actually reserve any space.  So we try
and reserve space here, but we cannot flush delalloc, so this forces us to
return -ENOSPC when in reality we have plenty of space.  The most common symptom
is seeing a bunch of "couldn't dirty inode" messages in syslog.  With
xfstests 224 we end up falling back to start_transaction and then doing all the
flush delalloc stuff which causes to hang for a very long time.

So instead steal from the global reserve, which is what this is meant for
anyway.  With this patch and the other 2 I have sent xfstests 224 now passes
successfully.  Thanks,

Signed-off-by: Josef Bacik <josef@redhat.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
This commit is contained in:
Josef Bacik 2011-01-24 21:43:20 +00:00 committed by Chris Mason
parent e9e22899de
commit 68a82277b8
1 changed files with 27 additions and 1 deletions
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28
fs/btrfs/extent-tree.c
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@ -5646,6 +5646,7 @@ use_block_rsv(struct btrfs_trans_handle *trans,
struct btrfs_root *root, u32 blocksize)
{
struct btrfs_block_rsv *block_rsv;
struct btrfs_block_rsv *global_rsv = &root->fs_info->global_block_rsv;
int ret;
block_rsv = get_block_rsv(trans, root);
@ -5653,14 +5654,39 @@ use_block_rsv(struct btrfs_trans_handle *trans,
if (block_rsv->size == 0) {
ret = reserve_metadata_bytes(trans, root, block_rsv,
blocksize, 0);
if (ret)
/*
* If we couldn't reserve metadata bytes try and use some from
* the global reserve.
*/
if (ret && block_rsv != global_rsv) {
ret = block_rsv_use_bytes(global_rsv, blocksize);
if (!ret)
return global_rsv;
return ERR_PTR(ret);
} else if (ret) {
return ERR_PTR(ret);
}
return block_rsv;
}
ret = block_rsv_use_bytes(block_rsv, blocksize);
if (!ret)
return block_rsv;
if (ret) {
WARN_ON(1);
ret = reserve_metadata_bytes(trans, root, block_rsv, blocksize,
0);
if (!ret) {
spin_lock(&block_rsv->lock);
block_rsv->size += blocksize;
spin_unlock(&block_rsv->lock);
return block_rsv;
} else if (ret && block_rsv != global_rsv) {
ret = block_rsv_use_bytes(global_rsv, blocksize);
if (!ret)
return global_rsv;
}
}
return ERR_PTR(-ENOSPC);
}