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Btrfs: avoid starting a transaction in the write path

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I noticed while looking at a deadlock that we are always starting a transaction
in cow_file_range().  This isn't really needed since we only need a transaction
if we are doing an inline extent, or if the allocator needs to allocate a chunk.
So push down all the transaction start stuff to be closer to where we actually
need a transaction in all of these cases.  This will hopefully reduce our write
latency when we are committing often.  Thanks,

Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>
This commit is contained in:
Josef Bacik
2013-08-14 14:02:47 -04:00
committed by Chris Mason
parent 9ffba8cda9
commit 00361589d2
6 changed files with 101 additions and 179 deletions
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11
fs/btrfs/file.c
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@@ -1339,7 +1339,6 @@ fail:
static noinline int check_can_nocow(struct inode *inode, loff_t pos,
size_t *write_bytes)
{
struct btrfs_trans_handle *trans;
struct btrfs_root *root = BTRFS_I(inode)->root;
struct btrfs_ordered_extent *ordered;
u64 lockstart, lockend;
@@ -1361,16 +1360,8 @@ static noinline int check_can_nocow(struct inode *inode, loff_t pos,
btrfs_put_ordered_extent(ordered);
}
trans = btrfs_join_transaction(root);
if (IS_ERR(trans)) {
unlock_extent(&BTRFS_I(inode)->io_tree, lockstart, lockend);
return PTR_ERR(trans);
}
num_bytes = lockend - lockstart + 1;
ret = can_nocow_extent(trans, inode, lockstart, &num_bytes, NULL, NULL,
NULL);
btrfs_end_transaction(trans, root);
ret = can_nocow_extent(inode, lockstart, &num_bytes, NULL, NULL, NULL);
if (ret <= 0) {
ret = 0;
} else {