From: "Matthew Wilcox (Oracle)" <[email protected]>
This simple helper will be the basis of the writeback iterator.
To make this work, we need to remember the current index
and end positions in writeback_control.
Signed-off-by: Matthew Wilcox (Oracle) <[email protected]>
Signed-off-by: Christoph Hellwig <[email protected]>
---
include/linux/writeback.h | 2 ++
mm/page-writeback.c | 49 +++++++++++++++++++++------------------
2 files changed, 29 insertions(+), 22 deletions(-)
diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index 05e8add4b5ae3c..be960f92ad9dbd 100644
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -81,6 +81,8 @@ struct writeback_control {
/* internal fields used by the ->writepages implementation: */
struct folio_batch fbatch;
+ pgoff_t index;
+ pgoff_t end; /* inclusive */
pgoff_t done_index;
int err;
unsigned range_whole:1; /* entire file */
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 45309f3b8193f8..5d33e7b468e2cc 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -2378,6 +2378,22 @@ static int writeback_finish(struct address_space *mapping,
return wbc->err;
}
+static void writeback_get_batch(struct address_space *mapping,
+ struct writeback_control *wbc)
+{
+ xa_mark_t tag;
+
+ if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages)
+ tag = PAGECACHE_TAG_TOWRITE;
+ else
+ tag = PAGECACHE_TAG_DIRTY;
+
+ folio_batch_release(&wbc->fbatch);
+ cond_resched();
+ filemap_get_folios_tag(mapping, &wbc->index, wbc->end, tag,
+ &wbc->fbatch);
+}
+
/**
* write_cache_pages - walk the list of dirty pages of the given address space and write all of them.
* @mapping: address space structure to write
@@ -2414,41 +2430,32 @@ int write_cache_pages(struct address_space *mapping,
void *data)
{
int error;
- int nr_folios;
- pgoff_t index;
- pgoff_t end; /* Inclusive */
- xa_mark_t tag;
if (wbc->range_cyclic) {
- index = mapping->writeback_index; /* prev offset */
- end = -1;
+ wbc->index = mapping->writeback_index; /* prev offset */
+ wbc->end = -1;
} else {
- index = wbc->range_start >> PAGE_SHIFT;
- end = wbc->range_end >> PAGE_SHIFT;
+ wbc->index = wbc->range_start >> PAGE_SHIFT;
+ wbc->end = wbc->range_end >> PAGE_SHIFT;
if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)
wbc->range_whole = 1;
}
- if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages) {
- tag_pages_for_writeback(mapping, index, end);
- tag = PAGECACHE_TAG_TOWRITE;
- } else {
- tag = PAGECACHE_TAG_DIRTY;
- }
+ if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages)
+ tag_pages_for_writeback(mapping, wbc->index, wbc->end);
- wbc->done_index = index;
+ wbc->done_index = wbc->index;
folio_batch_init(&wbc->fbatch);
wbc->err = 0;
- while (index <= end) {
+ while (wbc->index <= wbc->end) {
int i;
- nr_folios = filemap_get_folios_tag(mapping, &index, end,
- tag, &wbc->fbatch);
+ writeback_get_batch(mapping, wbc);
- if (nr_folios == 0)
+ if (wbc->fbatch.nr == 0)
break;
- for (i = 0; i < nr_folios; i++) {
+ for (i = 0; i < wbc->fbatch.nr; i++) {
struct folio *folio = wbc->fbatch.folios[i];
unsigned long nr;
@@ -2526,8 +2533,6 @@ int write_cache_pages(struct address_space *mapping,
wbc->sync_mode == WB_SYNC_NONE)
return writeback_finish(mapping, wbc, true);
}
- folio_batch_release(&wbc->fbatch);
- cond_resched();
}
return writeback_finish(mapping, wbc, false);
--
2.39.2
On Thu 14-12-23 14:25:35, Christoph Hellwig wrote:
> From: "Matthew Wilcox (Oracle)" <[email protected]>
>
> This simple helper will be the basis of the writeback iterator.
> To make this work, we need to remember the current index
> and end positions in writeback_control.
>
> Signed-off-by: Matthew Wilcox (Oracle) <[email protected]>
> Signed-off-by: Christoph Hellwig <[email protected]>
Just some nits:
> --- a/include/linux/writeback.h
> +++ b/include/linux/writeback.h
> @@ -81,6 +81,8 @@ struct writeback_control {
>
> /* internal fields used by the ->writepages implementation: */
> struct folio_batch fbatch;
> + pgoff_t index;
> + pgoff_t end; /* inclusive */
> pgoff_t done_index;
I don't think we need to cache 'end' since it isn't used that much. In
writeback_get_batch() we can just compute it locally as:
if (wbc->range_cyclic)
end = -1;
else
end = wbc->range_end >> PAGE_SHIFT;
and in the termination condition of the loop we can have it like:
while (wbc->range_cyclic || index <= wbc->range_end >> PAGE_SHIFT)
Also I don't think we need both done_index and index since they are closely
related and when spread over several functions it gets a bit confusing
what's for what. So I'd just remove done_index, use index instead for
setting writeback_index and just reset 'index' to the desired value in
those two cases where we break out of the loop early and thus index !=
done_index.
I'm sorry for nitpicking about these state variables but IMO reducing their
amount actually makes things easier to verify (and thus maintain) when they
are spread over several functions.
Honza
--
Jan Kara <[email protected]>
SUSE Labs, CR