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Subjectiomap-folio & nvdimm merge
On Thu, Dec 16, 2021 at 09:07:06PM +0000, Matthew Wilcox (Oracle) wrote:
> The zero iterator can work in folio-sized chunks instead of page-sized
> chunks. This will save a lot of page cache lookups if the file is cached
> in large folios.

This patch (and a few others) end up conflicting with what Christoph did
that's now in the nvdimm tree. In an effort to make the merge cleaner,
I took the next-20211220 tag and did the following:

Revert de291b590286
Apply: https://lore.kernel.org/linux-xfs/20211221044450.517558-1-willy@infradead.org/
(these two things are likely to happen in the nvdimm tree imminently)

I then checked out iomap-folio-5.17e and added this patch:

iomap: Inline __iomap_zero_iter into its caller

To make the merge easier, replicate the inlining of __iomap_zero_iter()
into iomap_zero_iter() that is currently in the nvdimm tree.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index ba80bedd9590..c6b3a148e898 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -895,27 +895,6 @@ iomap_file_unshare(struct inode *inode, loff_t pos, loff_t len,
}
EXPORT_SYMBOL_GPL(iomap_file_unshare);

-static s64 __iomap_zero_iter(struct iomap_iter *iter, loff_t pos, u64 length)
-{
- struct folio *folio;
- int status;
- size_t offset;
- size_t bytes = min_t(u64, SIZE_MAX, length);
-
- status = iomap_write_begin(iter, pos, bytes, &folio);
- if (status)
- return status;
-
- offset = offset_in_folio(folio, pos);
- if (bytes > folio_size(folio) - offset)
- bytes = folio_size(folio) - offset;
-
- folio_zero_range(folio, offset, bytes);
- folio_mark_accessed(folio);
-
- return iomap_write_end(iter, pos, bytes, bytes, folio);
-}
-
static loff_t iomap_zero_iter(struct iomap_iter *iter, bool *did_zero)
{
struct iomap *iomap = &iter->iomap;
@@ -929,14 +908,34 @@ static loff_t iomap_zero_iter(struct iomap_iter *iter, bool *did_zero)
return length;

do {
- s64 bytes;
+ struct folio *folio;
+ int status;
+ size_t offset;
+ size_t bytes = min_t(u64, SIZE_MAX, length);
+
+ if (IS_DAX(iter->inode)) {
+ s64 tmp = dax_iomap_zero(pos, bytes, iomap);
+ if (tmp < 0)
+ return tmp;
+ bytes = tmp;
+ goto good;
+ }

- if (IS_DAX(iter->inode))
- bytes = dax_iomap_zero(pos, length, iomap);
- else
- bytes = __iomap_zero_iter(iter, pos, length);
- if (bytes < 0)
- return bytes;
+ status = iomap_write_begin(iter, pos, bytes, &folio);
+ if (status)
+ return status;
+
+ offset = offset_in_folio(folio, pos);
+ if (bytes > folio_size(folio) - offset)
+ bytes = folio_size(folio) - offset;
+
+ folio_zero_range(folio, offset, bytes);
+ folio_mark_accessed(folio);
+
+ bytes = iomap_write_end(iter, pos, bytes, bytes, folio);
+good:
+ if (WARN_ON_ONCE(bytes == 0))
+ return -EIO;

pos += bytes;
length -= bytes;


Then I did the merge, and the merge commit looks pretty sensible
afterwards:

Merge branch 'iomap-folio-5.17f' into fixup

diff --cc fs/iomap/buffered-io.c
index 955f51f94b3f,c6b3a148e898..c938bbad075e
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@@ -888,19 -908,32 +907,23 @@@ static loff_t iomap_zero_iter(struct io
return length;
do {
- unsigned offset = offset_in_page(pos);
- size_t bytes = min_t(u64, PAGE_SIZE - offset, length);
- struct page *page;
+ struct folio *folio;
int status;
+ size_t offset;
+ size_t bytes = min_t(u64, SIZE_MAX, length);
- status = iomap_write_begin(iter, pos, bytes, &page);
- if (IS_DAX(iter->inode)) {
- s64 tmp = dax_iomap_zero(pos, bytes, iomap);
- if (tmp < 0)
- return tmp;
- bytes = tmp;
- goto good;
- }
-
+ status = iomap_write_begin(iter, pos, bytes, &folio);
if (status)
return status;
- zero_user(page, offset, bytes);
- mark_page_accessed(page);
+ offset = offset_in_folio(folio, pos);
+ if (bytes > folio_size(folio) - offset)
+ bytes = folio_size(folio) - offset;
+
+ folio_zero_range(folio, offset, bytes);
+ folio_mark_accessed(folio);
- bytes = iomap_write_end(iter, pos, bytes, bytes, page);
+ bytes = iomap_write_end(iter, pos, bytes, bytes, folio);
-good:
if (WARN_ON_ONCE(bytes == 0))
return -EIO;


Shall I push out a version of this patch series which includes the
"iomap: Inline __iomap_zero_iter into its caller" patch I pasted above?

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