On Friday 07 Aug 2015 11:08:30 Qu Wenruo wrote:
> Hi Chanda,
>
> Thanks for your effort to implement sub pagesize block size.
>
> These cleanups look quite good, but still some small readablity
> recommendation inlined below.
>
> Chandan Rajendra wrote on 2015/08/06 15:40 +0530:
> > Currently, the code reserves/releases extents in multiples of
> > PAGE_CACHE_SIZE units. Fix this by doing reservation/releases in block
> > size units.
> >
> > Signed-off-by: Chandan Rajendra <chan...@linux.vnet.ibm.com>
> > ---
> >
> > fs/btrfs/file.c | 40 ++++++++++++++++++++++++++++------------
> > 1 file changed, 28 insertions(+), 12 deletions(-)
> >
> > diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
> > index 795d754..e3b2b3c 100644
> > --- a/fs/btrfs/file.c
> > +++ b/fs/btrfs/file.c
> >
> > @@ -1362,16 +1362,19 @@ fail:
> > static noinline int
> > lock_and_cleanup_extent_if_need(struct inode *inode, struct page
> > **pages,
> >
> > size_t num_pages, loff_t pos,
> >
> > + size_t write_bytes,
> >
> > u64 *lockstart, u64 *lockend,
> > struct extent_state **cached_state)
> >
> > {
> >
> > + struct btrfs_root *root = BTRFS_I(inode)->root;
> >
> > u64 start_pos;
> > u64 last_pos;
> > int i;
> > int ret = 0;
> >
> > - start_pos = pos & ~((u64)PAGE_CACHE_SIZE - 1);
> > - last_pos = start_pos + ((u64)num_pages << PAGE_CACHE_SHIFT) - 1;
> > + start_pos = pos & ~((u64)root->sectorsize - 1);
>
> Why not just roundown(pos, root->sectorisze)
> Hard coded align is never that easy to read.
Qu Wenruo, Thanks for pointing it out. I will replace them with
round_[down,up] calls and post V2.
>
> > + last_pos = start_pos
> > + + ALIGN(pos + write_bytes - start_pos, root->sectorsize) - 1;
>
> Maybe just a preference problem, I'd prefer to use round_down other than
> ALIGN, as sometimes I still need to figure out if it is round_down or
> round_down.
>
> > if (start_pos < inode->i_size) {
> >
> > struct btrfs_ordered_extent *ordered;
> >
> > @@ -1489,6 +1492,7 @@ static noinline ssize_t
> > __btrfs_buffered_write(struct file *file,>
> > while (iov_iter_count(i) > 0) {
> >
> > size_t offset = pos & (PAGE_CACHE_SIZE - 1);
> >
> > + size_t sector_offset;
> >
> > size_t write_bytes = min(iov_iter_count(i),
> >
> > nrptrs * (size_t)PAGE_CACHE_SIZE -
> > offset);
> >
> > @@ -1497,6 +1501,8 @@ static noinline ssize_t
> > __btrfs_buffered_write(struct file *file,>
> > size_t reserve_bytes;
> > size_t dirty_pages;
> > size_t copied;
> >
> > + size_t dirty_sectors;
> > + size_t num_sectors;
> >
> > WARN_ON(num_pages > nrptrs);
> >
> > @@ -1509,8 +1515,12 @@ static noinline ssize_t
> > __btrfs_buffered_write(struct file *file,>
> > break;
> >
> > }
> >
> > - reserve_bytes = num_pages << PAGE_CACHE_SHIFT;
> > + sector_offset = pos & (root->sectorsize - 1);
>
> Same here.
>
> Thanks,
> Qu
>
> > + reserve_bytes = ALIGN(write_bytes + sector_offset,
> > + root->sectorsize);
> > +
> >
> > ret = btrfs_check_data_free_space(inode, reserve_bytes,
write_bytes);
> >
> > +
> >
> > if (ret == -ENOSPC &&
> >
> > (BTRFS_I(inode)->flags & (BTRFS_INODE_NODATACOW |
> >
> > BTRFS_INODE_PREALLOC))) {
> >
> > @@ -1523,7 +1533,9 @@ static noinline ssize_t
> > __btrfs_buffered_write(struct file *file,>
> > */
> >
> > num_pages = DIV_ROUND_UP(write_bytes + offset,
> >
> > PAGE_CACHE_SIZE);
> >
> > - reserve_bytes = num_pages << PAGE_CACHE_SHIFT;
> > + reserve_bytes = ALIGN(write_bytes +
sector_offset,
> > + root->sectorsize);
> > +
> >
> > ret = 0;
> >
> > } else {
> >
> > ret = -ENOSPC;
> >
> > @@ -1558,8 +1570,8 @@ again:
> > break;
> >
> > ret = lock_and_cleanup_extent_if_need(inode, pages, num_pages,
> >
> > - pos, &lockstart,
&lockend,
> > - &cached_state);
> > + pos, write_bytes, &lockstart,
> > + &lockend, &cached_state);
> >
> > if (ret < 0) {
> >
> > if (ret == -EAGAIN)
> >
> > goto again;
> >
> > @@ -1595,9 +1607,14 @@ again:
> > * we still have an outstanding extent for the chunk we
actually
> > * managed to copy.
> > */
> >
> > - if (num_pages > dirty_pages) {
> > - release_bytes = (num_pages - dirty_pages) <<
> > - PAGE_CACHE_SHIFT;
> > + num_sectors = reserve_bytes >> inode->i_blkbits;
> > + dirty_sectors = round_up(copied + sector_offset,
> > + root->sectorsize);
> > + dirty_sectors >>= inode->i_blkbits;
> > +
> > + if (num_sectors > dirty_sectors) {
> > + release_bytes = (write_bytes - copied)
> > + & ~((u64)root->sectorsize - 1);
> >
> > if (copied > 0) {
> >
> > spin_lock(&BTRFS_I(inode)->lock);
> > BTRFS_I(inode)->outstanding_extents++;
> >
> > @@ -1611,7 +1628,7 @@ again:
> > release_bytes);
> >
> > }
> >
> > - release_bytes = dirty_pages << PAGE_CACHE_SHIFT;
> > + release_bytes = ALIGN(copied + sector_offset, root-
>sectorsize);
> >
> > if (copied > 0)
> >
> > ret = btrfs_dirty_pages(root, inode, pages,
> >
> > @@ -1632,8 +1649,7 @@ again:
> > if (only_release_metadata && copied > 0) {
> >
> > lockstart = round_down(pos, root->sectorsize);
> >
> > - lockend = lockstart +
> > - (dirty_pages << PAGE_CACHE_SHIFT) - 1;
> > + lockend = round_up(pos + copied, root->sectorsize) -
1;
> >
> > set_extent_bit(&BTRFS_I(inode)->io_tree, lockstart,
> >
> > lockend, EXTENT_NORESERVE, NULL,
--
chandan
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