Re: [PATCH] Btrfs: avoid unnecessarily locking inode when clearing a range
From: Chris Mason <clm@fb.com>
Date: 2017-08-03 15:02:18
On 07/27/2017 02:52 PM, fdmanana@kernel.org wrote:
From: Filipe Manana <redacted> If the range being cleared was not marked for defrag and we are not about to clear the range from the defrag status, we don't need to lock and unlock the inode. Signed-off-by: Filipe Manana <redacted>
Thanks Filipe, looks like it goes all the way back to:
commit 47059d930f0e002ff851beea87d738146804726d
Author: Wang Shilong [off-list ref]
Date: Thu Jul 3 18:22:07 2014 +0800
Btrfs: make defragment work with nodatacow option
I can't see how the inode lock is required here.
Reviewed-by: Chris Mason <clm@fb.com>
-chris
quoted hunk ↗ jump to hunk
--- fs/btrfs/inode.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index eb495e956d53..51c45c0a8553 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c@@ -1797,10 +1797,11 @@ static void btrfs_clear_bit_hook(void *private_data, u64 len = state->end + 1 - state->start; u32 num_extents = count_max_extents(len); - spin_lock(&inode->lock); - if ((state->state & EXTENT_DEFRAG) && (*bits & EXTENT_DEFRAG)) + if ((state->state & EXTENT_DEFRAG) && (*bits & EXTENT_DEFRAG)) { + spin_lock(&inode->lock); inode->defrag_bytes -= len; - spin_unlock(&inode->lock); + spin_unlock(&inode->lock); + } /* * set_bit and clear bit hooks normally require _irqsave/restore