[PATCH v10 12/14] btrfs: send: allocate send buffer with alloc_page() and vmap() for v2

Omar Sandoval
2021-08-17T21:07:35Z

From: Omar Sandoval <osandov@fb.com>

For encoded writes, we need the raw pages for reading compressed data
directly via a bio. So, replace kvmalloc() with vmap() so we have access
to the raw pages. 144k is large enough that it usually gets allocated
with vmalloc(), anyways.

Signed-off-by: Omar Sandoval <osandov@fb.com>
---
fs/btrfs/send.c | 33 +++++++++++++++++++++++++++++++--
1 file changed, 31 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
index dfe598d12b8c..7242362ecb23 100644
--- a/fs/btrfs/send.c
+++ b/fs/btrfs/send.c
@@ -81,6 +81,7 @@ struct send_ctx {
char *send_buf;
u32 send_size;
u32 send_max_size;
+ struct page **send_buf_pages;
u64 total_send_size;
u64 cmd_send_size[BTRFS_SEND_C_MAX + 1];
u64 flags; /* 'flags' member of btrfs_ioctl_send_args is u64 */
@@ -7230,6 +7231,7 @@ long btrfs_ioctl_send(struct file *mnt_file, struct btrfs_ioctl_send_args *arg)
struct btrfs_root *clone_root;
struct send_ctx *sctx = NULL;
u32 i;
+ u32 send_buf_num_pages = 0;
u64 *clone_sources_tmp = NULL;
int clone_sources_to_rollback = 0;
size_t alloc_size;
@@ -7310,10 +7312,28 @@ long btrfs_ioctl_send(struct file *mnt_file, struct btrfs_ioctl_send_args *arg)
if (sctx->flags & BTRFS_SEND_FLAG_STREAM_V2) {
sctx->send_max_size = ALIGN(SZ_16K + BTRFS_MAX_COMPRESSED,
PAGE_SIZE);
+ 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) {
+ send_buf_num_pages = 0;
+ ret = -ENOMEM;
+ goto out;
+ }
+ for (i = 0; i < send_buf_num_pages; i++) {
+ sctx->send_buf_pages[i] = alloc_page(GFP_KERNEL);
+ if (!sctx->send_buf_pages[i]) {
+ ret = -ENOMEM;
+ goto out;
+ }
+ }
+ sctx->send_buf = vmap(sctx->send_buf_pages, send_buf_num_pages,
+ VM_MAP, PAGE_KERNEL);
} 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;
@@ -7520,7 +7540,16 @@ long btrfs_ioctl_send(struct file *mnt_file, struct btrfs_ioctl_send_args *arg)
fput(sctx->send_filp);

kvfree(sctx->clone_roots);
- kvfree(sctx->send_buf);
+ if (sctx->flags & BTRFS_SEND_FLAG_STREAM_V2) {
+ vunmap(sctx->send_buf);
+ for (i = 0; i < send_buf_num_pages; i++) {
+ if (sctx->send_buf_pages[i])
+ __free_page(sctx->send_buf_pages[i]);
+ }
+ kfree(sctx->send_buf_pages);
+ } else {
+ kvfree(sctx->send_buf);
+ }

name_cache_free(sctx);

--
2.32.0