On 18:14 26/02, David Sterba wrote:
> On Thu, Feb 25, 2021 at 02:58:22PM -0600, Goldwyn Rodrigues wrote:
> > force_nocow can be calculated by btrfs_inode and does not need to be
> > passed as an argument.
> >
> > This simplifies run_delalloc_nocow() call from btrfs_run_delalloc_range()
> > since the decision whether the extent is cow'd or not can be derived
> > from need_force_cow(). Since BTRFS_INODE_NODATACOW and
> > BTRFS_INODE_PREALLOC flags are checked in need_force_cow(), there is
> > no need to check it again.
> >
> > Signed-off-by: Goldwyn Rodrigues <[email protected]>
> >
> > Change since v1:
> > - Kept need_force_cow() as it is
>
> Added to misc-next, thanks.
>
> > ---
> > fs/btrfs/inode.c | 12 ++++--------
> > 1 file changed, 4 insertions(+), 8 deletions(-)
> >
> > diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> > index 4f2f1e932751..e5dd8d7ef0c8 100644
> > --- a/fs/btrfs/inode.c
> > +++ b/fs/btrfs/inode.c
> > @@ -1516,7 +1516,7 @@ static int fallback_to_cow(struct btrfs_inode *inode,
> > struct page *locked_page,
> > static noinline int run_delalloc_nocow(struct btrfs_inode *inode,
> > struct page *locked_page,
> > const u64 start, const u64 end,
> > - int *page_started, int force,
> > + int *page_started,
> > unsigned long *nr_written)
> > {
> > struct btrfs_fs_info *fs_info = inode->root->fs_info;
> > @@ -1530,6 +1530,7 @@ static noinline int run_delalloc_nocow(struct
> > btrfs_inode *inode,
> > u64 ino = btrfs_ino(inode);
> > bool nocow = false;
> > u64 disk_bytenr = 0;
> > + bool force = inode->flags & BTRFS_INODE_NODATACOW;
> >
> > path = btrfs_alloc_path();
> > if (!path) {
> > @@ -1891,17 +1892,12 @@ int btrfs_run_delalloc_range(struct btrfs_inode
> > *inode, struct page *locked_page
> > struct writeback_control *wbc)
> > {
> > int ret;
> > - int force_cow = need_force_cow(inode, start, end);
> > const bool zoned = btrfs_is_zoned(inode->root->fs_info);
> >
> > - if (inode->flags & BTRFS_INODE_NODATACOW && !force_cow) {
> > + if (!need_force_cow(inode, start, end)) {
>
> We may want to reverse the logic and naming so it says
> 'need_force_nocow', right now it's "we don't need to force COW, so let's
> do NOCOW", because COW is the default and the condition should pick the
> exceptional case.
Calling it need_force_nocow() or should_nocow() will result in the same
concept as previous patch where EXTENT_DEFRAG range would need to be
checked before checking inode flags BTRFS_INODE_NODATACOW and
BTRFS_INODE_PREALLOC. That's because EXTENT_DEFRAG in range
should result in a COW sequence immaterial of what CoW sequence the
inode flags say. Isn't it?
Maybe something like this would keep inode flags checks earlier than
test_range_bit():
static inline bool should_nocow(struct btrfs_inode *inode, u64 start, u64 end)
{
if (inode->flags & (BTRFS_INODE_NODATACOW | BTRFS_INODE_PREALLOC)) {
if (inode->defrag_bytes &&
test_range_bit(&inode->io_tree, start, end, EXTENT_DEFRAG,
0, NULL))
return false;
return true;
}
return false;
}
>
> > ASSERT(!zoned);
> > ret = run_delalloc_nocow(inode, locked_page, start, end,
> > - page_started, 1, nr_written);
> > - } else if (inode->flags & BTRFS_INODE_PREALLOC && !force_cow) {
> > - ASSERT(!zoned);
> > - ret = run_delalloc_nocow(inode, locked_page, start, end,
> > - page_started, 0, nr_written);
> > + page_started, nr_written);
> > } else if (!inode_can_compress(inode) ||
> > !inode_need_compress(inode, start, end)) {
> > if (zoned)
--
Goldwyn
