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Message-ID: <CAHpGcM+qhur4C2fLyR-dQx7CvumXVvMAM5NBCCXnL5ve-2qE8w@mail.gmail.com>
Date: Tue, 20 Jul 2021 13:34:58 +0200
From: Andreas Grünbacher <andreas.gruenbacher@...il.com>
To: Gao Xiang <hsiangkao@...ux.alibaba.com>
Cc: linux-erofs@...ts.ozlabs.org,
Linux FS-devel Mailing List <linux-fsdevel@...r.kernel.org>,
LKML <linux-kernel@...r.kernel.org>,
Christoph Hellwig <hch@....de>,
"Darrick J . Wong" <djwong@...nel.org>,
Matthew Wilcox <willy@...radead.org>
Subject: Re: [PATCH v3] iomap: support tail packing inline read
Am Mo., 19. Juli 2021 um 16:48 Uhr schrieb Gao Xiang
<hsiangkao@...ux.alibaba.com>:
> This tries to add tail packing inline read to iomap, which can support
> several inline tail blocks. Similar to the previous approach, it cleans
> post-EOF in one iteration.
>
> The write path remains untouched since EROFS cannot be used for testing.
> It'd be better to be implemented if upcoming real users care rather than
> leave untested dead code around.
>
> Cc: Christoph Hellwig <hch@....de>
> Cc: Darrick J. Wong <djwong@...nel.org>
> Cc: Matthew Wilcox <willy@...radead.org>
> Cc: Andreas Gruenbacher <andreas.gruenbacher@...il.com>
> Signed-off-by: Gao Xiang <hsiangkao@...ux.alibaba.com>
> ---
> v2: https://lore.kernel.org/r/YPLdSja%2F4FBsjss%2F@B-P7TQMD6M-0146.local/
> changes since v2:
> - update suggestion from Christoph:
> https://lore.kernel.org/r/YPVe41YqpfGLNsBS@infradead.org/
>
> Hi Andreas,
> would you mind test on the gfs2 side? Thanks in advance!
>
> Thanks,
> Gao Xiang
>
> fs/iomap/buffered-io.c | 50 ++++++++++++++++++++++++++----------------
> fs/iomap/direct-io.c | 11 ++++++----
> 2 files changed, 38 insertions(+), 23 deletions(-)
>
> diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> index 87ccb3438bec..cac8a88660d8 100644
> --- a/fs/iomap/buffered-io.c
> +++ b/fs/iomap/buffered-io.c
> @@ -207,23 +207,22 @@ struct iomap_readpage_ctx {
>
> static void
> iomap_read_inline_data(struct inode *inode, struct page *page,
> - struct iomap *iomap)
> + struct iomap *iomap, loff_t pos)
> {
> - size_t size = i_size_read(inode);
> + unsigned int size, poff = offset_in_page(pos);
> void *addr;
>
> - if (PageUptodate(page))
> - return;
> -
> - BUG_ON(page_has_private(page));
> - BUG_ON(page->index);
> - BUG_ON(size > PAGE_SIZE - offset_in_page(iomap->inline_data));
> + /* inline source data must be inside a single page */
> + BUG_ON(iomap->length > PAGE_SIZE - offset_in_page(iomap->inline_data));
> + /* handle tail-packing blocks cross the current page into the next */
> + size = min_t(unsigned int, iomap->length + pos - iomap->offset,
> + PAGE_SIZE - poff);
>
> addr = kmap_atomic(page);
> - memcpy(addr, iomap->inline_data, size);
> - memset(addr + size, 0, PAGE_SIZE - size);
> + memcpy(addr + poff, iomap->inline_data - iomap->offset + pos, size);
> + memset(addr + poff + size, 0, PAGE_SIZE - poff - size);
> kunmap_atomic(addr);
> - SetPageUptodate(page);
> + iomap_set_range_uptodate(page, poff, PAGE_SIZE - poff);
> }
>
> static inline bool iomap_block_needs_zeroing(struct inode *inode,
> @@ -246,18 +245,19 @@ iomap_readpage_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
> unsigned poff, plen;
> sector_t sector;
>
> - if (iomap->type == IOMAP_INLINE) {
> - WARN_ON_ONCE(pos);
> - iomap_read_inline_data(inode, page, iomap);
> - return PAGE_SIZE;
> - }
> -
> - /* zero post-eof blocks as the page may be mapped */
> iop = iomap_page_create(inode, page);
We can skip creating the iop when reading the entire page.
> + /* needs to skip some leading uptodated blocks */
> iomap_adjust_read_range(inode, iop, &pos, length, &poff, &plen);
> if (plen == 0)
> goto done;
>
> + if (iomap->type == IOMAP_INLINE) {
> + iomap_read_inline_data(inode, page, iomap, pos);
> + plen = PAGE_SIZE - poff;
> + goto done;
> + }
> +
> + /* zero post-eof blocks as the page may be mapped */
> if (iomap_block_needs_zeroing(inode, iomap, pos)) {
> zero_user(page, poff, plen);
> iomap_set_range_uptodate(page, poff, plen);
> @@ -589,6 +589,18 @@ __iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, int flags,
> return 0;
> }
>
> +static int iomap_write_begin_inline(struct inode *inode, loff_t pos,
> + struct page *page, struct iomap *srcmap)
> +{
> + /* needs more work for the tailpacking case, disable for now */
> + if (WARN_ON_ONCE(pos != 0))
> + return -EIO;
> + if (PageUptodate(page))
> + return 0;
> + iomap_read_inline_data(inode, page, srcmap, pos);
> + return 0;
> +}
> +
> static int
> iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags,
> struct page **pagep, struct iomap *iomap, struct iomap *srcmap)
> @@ -618,7 +630,7 @@ iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags,
> }
>
> if (srcmap->type == IOMAP_INLINE)
> - iomap_read_inline_data(inode, page, srcmap);
> + status = iomap_write_begin_inline(inode, pos, page, srcmap);
> else if (iomap->flags & IOMAP_F_BUFFER_HEAD)
> status = __block_write_begin_int(page, pos, len, NULL, srcmap);
> else
> diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
> index 9398b8c31323..ee6309967b77 100644
> --- a/fs/iomap/direct-io.c
> +++ b/fs/iomap/direct-io.c
> @@ -379,22 +379,25 @@ iomap_dio_inline_actor(struct inode *inode, loff_t pos, loff_t length,
> {
> struct iov_iter *iter = dio->submit.iter;
> size_t copied;
> + void *dst = iomap->inline_data + pos - iomap->offset;
>
> - BUG_ON(pos + length > PAGE_SIZE - offset_in_page(iomap->inline_data));
> + /* inline data must be inside a single page */
> + BUG_ON(length > PAGE_SIZE - offset_in_page(iomap->inline_data));
>
> if (dio->flags & IOMAP_DIO_WRITE) {
> loff_t size = inode->i_size;
>
> if (pos > size)
> - memset(iomap->inline_data + size, 0, pos - size);
> - copied = copy_from_iter(iomap->inline_data + pos, length, iter);
> + memset(iomap->inline_data + size - iomap->offset,
> + 0, pos - size);
> + copied = copy_from_iter(dst, length, iter);
> if (copied) {
> if (pos + copied > size)
> i_size_write(inode, pos + copied);
> mark_inode_dirty(inode);
> }
> } else {
> - copied = copy_to_iter(iomap->inline_data + pos, length, iter);
> + copied = copy_to_iter(dst, length, iter);
> }
> dio->size += copied;
> return copied;
> --
> 2.24.4
>
Thanks,
Andreas
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