On 10/27/23 17:41, Pankaj Raghav wrote:
On 27/10/2023 12:47, Matthew Wilcox wrote:
On Fri, Oct 27, 2023 at 10:03:15AM +0200, Pankaj Raghav wrote:
I also noticed this pattern in fscrypt_zeroout_range_inline_crypt().
Probably there are more places which could use a ZERO_FOLIO directly
instead of iterating with ZERO_PAGE.
Chinner also had a similar comment. It would be nice if we can reserve
a zero huge page that is the size of MAX_PAGECACHE_ORDER and add it as
one folio to the bio.
i'm on holiday atm. start looking at mm_get_huge_zero_page()
Thanks for the pointer. I made a rough version of how it might
look like if I use that API:
diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
index bcd3f8cf5ea4..6ae21bd16dbe 100644
--- a/fs/iomap/direct-io.c
+++ b/fs/iomap/direct-io.c
@@ -236,17 +236,43 @@ static void iomap_dio_zero(const struct iomap_iter *iter, struct iomap_dio *dio,
loff_t pos, unsigned len)
{
struct inode *inode = file_inode(dio->iocb->ki_filp);
- struct page *page = ZERO_PAGE(0);
+ struct page *page = NULL;
+ bool huge_page = false;
+ bool fallback = false;
struct bio *bio;
- bio = iomap_dio_alloc_bio(iter, dio, 1, REQ_OP_WRITE | REQ_SYNC | REQ_IDLE);
+ if (len > PAGE_SIZE) {
+ page = mm_get_huge_zero_page(current->mm);
+ if (likely(page))
+ huge_page = true;
+ }
+
+ if (!huge_page)
+ page = ZERO_PAGE(0);
+
+ fallback = ((len > PAGE_SIZE) && !huge_page);
+
That is pointless.
Bios can handle pages larger than PAGE_SIZE.
+ bio = iomap_dio_alloc_bio(iter, dio, BIO_MAX_VECS,
+ REQ_OP_WRITE | REQ_SYNC | REQ_IDLE);
Similar here. Just allocate space for a single folio.
fscrypt_set_bio_crypt_ctx(bio, inode, pos >> inode->i_blkbits,
GFP_KERNEL);
+
bio->bi_iter.bi_sector = iomap_sector(&iter->iomap, pos);
bio->bi_private = dio;
bio->bi_end_io = iomap_dio_bio_end_io;
- __bio_add_page(bio, page, len, 0);
+ if (!fallback) {
+ bio_add_folio_nofail(bio, page_folio(page), len, 0);
+ } else {
+ while (len) {
+ unsigned int io_len =
+ min_t(unsigned int, len, PAGE_SIZE);
+
+ __bio_add_page(bio, page, io_len, 0);
+ len -= io_len;
+ }
+ }
See above. Kill the 'fallback' case.
Cheers,
Hannes
--
Dr. Hannes Reinecke Kernel Storage Architect
hare@xxxxxxx +49 911 74053 688
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