iomap: limit buffered I/O size to 128M

Currently iomap can build extremely large bios (I've seen sizes
up to 480MB).  Limit this to a lower bound so that the soon to
be added per-ioend integrity buffer doesn't go beyond what the
page allocator can support.

Signed-off-by: Christoph Hellwig <hch@lst.de>

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 06990e01288463c13b8494d1ffdbc6f8944b09cd..71bb676d499887e1596cc093476aa7436ebaf1a4 100644 (file)
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -456,6 +456,7 @@ static loff_t iomap_readpage_iter(const struct iomap_iter *iter,
        sector = iomap_sector(iomap, pos);
        if (!ctx->bio ||
            bio_end_sector(ctx->bio) != sector ||
+           ctx->bio->bi_iter.bi_size > SZ_128M ||
            !bio_add_folio(ctx->bio, folio, plen, poff)) {
                if (ctx->bio)
                        iomap_read_submit_bio(iter, ctx);
@@ -1674,6 +1675,8 @@ static struct iomap_ioend *iomap_alloc_ioend(struct iomap_writepage_ctx *wpc,
 static bool iomap_can_add_to_ioend(struct iomap_writepage_ctx *wpc, loff_t pos,
                u16 ioend_flags)
 {
+       if (wpc->ioend->io_bio.bi_iter.bi_size > SZ_128M)
+               return false;
        if (ioend_flags & IOMAP_IOEND_BOUNDARY)
                return false;
        if ((ioend_flags & IOMAP_IOEND_NOMERGE_FLAGS) !=