If REQ_NOWAIT is set, then do a non-blocking allocation if the operation is a write and we need to insert a new page. Currently REQ_NOWAIT cannot be set as the queue isn't marked as supporting nowait, this change is in preparation for allowing that.

Cc: stable@vger.kernel.org # 5.10+ Signed-off-by: Jens Axboe axboe@kernel.dk --- drivers/block/brd.c | 39 ++++++++++++++++++++++----------------- 1 file changed, 22 insertions(+), 17 deletions(-)

diff --git a/drivers/block/brd.c b/drivers/block/brd.c index 15a148d5aad9..1ddada0cdaca 100644 --- a/drivers/block/brd.c +++ b/drivers/block/brd.c @@ -80,26 +80,20 @@ static struct page *brd_lookup_page(struct brd_device *brd, sector_t sector) /* * Insert a new page for a given sector, if one does not already exist. */ -static int brd_insert_page(struct brd_device *brd, sector_t sector) +static int brd_insert_page(struct brd_device *brd, sector_t sector, gfp_t gfp) { pgoff_t idx; struct page *page; - gfp_t gfp_flags;

page = brd_lookup_page(brd, sector); if (page) return 0;

- /* - * Must use NOIO because we don't want to recurse back into the - * block or filesystem layers from page reclaim. - */ - gfp_flags = GFP_NOIO | __GFP_ZERO | __GFP_HIGHMEM; - page = alloc_page(gfp_flags); + page = alloc_page(gfp | __GFP_ZERO | __GFP_HIGHMEM); if (!page) return -ENOMEM;

- if (radix_tree_preload(GFP_NOIO)) { + if (radix_tree_preload(gfp)) { __free_page(page); return -ENOMEM; } @@ -167,19 +161,20 @@ static void brd_free_pages(struct brd_device *brd) /* * copy_to_brd_setup must be called before copy_to_brd. It may sleep. */ -static int copy_to_brd_setup(struct brd_device *brd, sector_t sector, size_t n) +static int copy_to_brd_setup(struct brd_device *brd, sector_t sector, size_t n, + gfp_t gfp) { unsigned int offset = (sector & (PAGE_SECTORS-1)) << SECTOR_SHIFT; size_t copy; int ret;

copy = min_t(size_t, n, PAGE_SIZE - offset); - ret = brd_insert_page(brd, sector); + ret = brd_insert_page(brd, sector, gfp); if (ret) return ret; if (copy < n) { sector += copy >> SECTOR_SHIFT; - ret = brd_insert_page(brd, sector); + ret = brd_insert_page(brd, sector, gfp); } return ret; } @@ -254,20 +249,26 @@ static void copy_from_brd(void *dst, struct brd_device *brd, * Process a single bvec of a bio. */ static int brd_do_bvec(struct brd_device *brd, struct page *page, - unsigned int len, unsigned int off, enum req_op op, + unsigned int len, unsigned int off, blk_opf_t opf, sector_t sector) { void *mem; int err = 0;

- if (op_is_write(op)) { - err = copy_to_brd_setup(brd, sector, len); + if (op_is_write(opf)) { + /* + * Must use NOIO because we don't want to recurse back into the + * block or filesystem layers from page reclaim. + */ + gfp_t gfp = opf & REQ_NOWAIT ? GFP_NOWAIT : GFP_NOIO; + + err = copy_to_brd_setup(brd, sector, len, gfp); if (err) goto out; }

mem = kmap_atomic(page); - if (!op_is_write(op)) { + if (!op_is_write(opf)) { copy_from_brd(mem + off, brd, sector, len); flush_dcache_page(page); } else { @@ -296,8 +297,12 @@ static void brd_submit_bio(struct bio *bio) (len & (SECTOR_SIZE - 1)));

err = brd_do_bvec(brd, bvec.bv_page, len, bvec.bv_offset, - bio_op(bio), sector); + bio->bi_opf, sector); if (err) { + if (err == -ENOMEM && bio->bi_opf & REQ_NOWAIT) { + bio_wouldblock_error(bio); + return; + } bio_io_error(bio); return; }