2019-06-07 13:14:28

by Naohiro Aota

Subject: [PATCH 16/19] btrfs: wait existing extents before truncating

When truncating a file, file buffers which have already been allocated but
not yet written may be truncated. Truncating these buffers could cause
breakage of a sequential write pattern in a block group if the truncated
blocks are for example followed by blocks allocated to another file. To
avoid this problem, always wait for write out of all unwritten buffers
before proceeding with the truncate execution.

Signed-off-by: Naohiro Aota <[email protected]>
---
fs/btrfs/inode.c | 11 +++++++++++
1 file changed, 11 insertions(+)

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 89542c19d09e..4e8c7921462f 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -5137,6 +5137,17 @@ static int btrfs_setsize(struct inode *inode, struct iattr *attr)
btrfs_end_write_no_snapshotting(root);
btrfs_end_transaction(trans);
} else {
+ struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
+
+ if (btrfs_fs_incompat(fs_info, HMZONED)) {
+ u64 sectormask = fs_info->sectorsize - 1;
+
+ ret = btrfs_wait_ordered_range(inode,
+ newsize & (~sectormask),
+ (u64)-1);
+ if (ret)
+ return ret;
+ }

/*
* We're truncating a file that used to have good data down to
--
2.21.0

2019-06-13 15:03:46

by Josef Bacik

Subject: Re: [PATCH 16/19] btrfs: wait existing extents before truncating

On Fri, Jun 07, 2019 at 10:10:22PM +0900, Naohiro Aota wrote:
> When truncating a file, file buffers which have already been allocated but
> not yet written may be truncated. Truncating these buffers could cause
> breakage of a sequential write pattern in a block group if the truncated
> blocks are for example followed by blocks allocated to another file. To
> avoid this problem, always wait for write out of all unwritten buffers
> before proceeding with the truncate execution.
>
> Signed-off-by: Naohiro Aota <[email protected]>
> ---
> fs/btrfs/inode.c | 11 +++++++++++
> 1 file changed, 11 insertions(+)
>
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index 89542c19d09e..4e8c7921462f 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -5137,6 +5137,17 @@ static int btrfs_setsize(struct inode *inode, struct iattr *attr)
> btrfs_end_write_no_snapshotting(root);
> btrfs_end_transaction(trans);
> } else {
> + struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
> +
> + if (btrfs_fs_incompat(fs_info, HMZONED)) {
> + u64 sectormask = fs_info->sectorsize - 1;
> +
> + ret = btrfs_wait_ordered_range(inode,
> + newsize & (~sectormask),
> + (u64)-1);

Use ALIGN(). Thanks,

Josef