From a4b333f2277b13eaf15b09235b243b8eda891d3d Mon Sep 17 00:00:00 2001 From: Omar Sandoval Date: Mon, 4 Apr 2022 10:29:07 -0700 Subject: [PATCH] btrfs: send: get send buffer pages for protocol v2 For encoded writes in send v2, we will get the encoded data with btrfs_encoded_read_regular_fill_pages(), which expects a list of raw pages. To avoid extra buffers and copies, we should read directly into the send buffer. Therefore, we need the raw pages for the send buffer. We currently allocate the send buffer with kvmalloc(), which may return a kmalloc'd buffer or a vmalloc'd buffer. For vmalloc, we can get the pages with vmalloc_to_page(). For kmalloc, we could use virt_to_page(). However, the buffer size we use (144K) is not a power of two, which in theory is not guaranteed to return a page-aligned buffer, and in practice would waste a lot of memory due to rounding up to the next power of two. 144K is large enough that it usually gets allocated with vmalloc(), anyways. So, for send v2, replace kvmalloc() with vmalloc() and save the pages in an array. Signed-off-by: Omar Sandoval Signed-off-by: David Sterba --- fs/btrfs/send.c | 29 +++++++++++++++++++++++++---- 1 file changed, 25 insertions(+), 4 deletions(-) diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c index 02df948..57052fe 100644 --- a/fs/btrfs/send.c +++ b/fs/btrfs/send.c @@ -87,6 +87,7 @@ struct send_ctx { * command (since protocol v2, data must be the last attribute). */ bool put_data; + struct page **send_buf_pages; u64 flags; /* 'flags' member of btrfs_ioctl_send_args is u64 */ /* Protocol version compatibility requested */ u32 proto; @@ -7575,12 +7576,31 @@ long btrfs_ioctl_send(struct inode *inode, struct btrfs_ioctl_send_args *arg) sctx->clone_roots_cnt = arg->clone_sources_count; - if (sctx->proto >= 2) + if (sctx->proto >= 2) { + u32 send_buf_num_pages; + sctx->send_max_size = ALIGN(SZ_16K + BTRFS_MAX_COMPRESSED, PAGE_SIZE); - else + sctx->send_buf = vmalloc(sctx->send_max_size); + if (!sctx->send_buf) { + ret = -ENOMEM; + goto out; + } + send_buf_num_pages = sctx->send_max_size >> PAGE_SHIFT; + sctx->send_buf_pages = kcalloc(send_buf_num_pages, + sizeof(*sctx->send_buf_pages), + GFP_KERNEL); + if (!sctx->send_buf_pages) { + ret = -ENOMEM; + goto out; + } + for (i = 0; i < send_buf_num_pages; i++) { + sctx->send_buf_pages[i] = + vmalloc_to_page(sctx->send_buf + (i << PAGE_SHIFT)); + } + } else { sctx->send_max_size = BTRFS_SEND_BUF_SIZE_V1; - - sctx->send_buf = kvmalloc(sctx->send_max_size, GFP_KERNEL); + sctx->send_buf = kvmalloc(sctx->send_max_size, GFP_KERNEL); + } if (!sctx->send_buf) { ret = -ENOMEM; goto out; @@ -7773,6 +7793,7 @@ out: fput(sctx->send_filp); kvfree(sctx->clone_roots); + kfree(sctx->send_buf_pages); kvfree(sctx->send_buf); name_cache_free(sctx); -- 2.7.4