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[v2,07/16] btrfs: send: Proactively round up to kmalloc bucket size

Message ID 20220923202822.2667581-8-keescook@chromium.org
State New
Headers show
Series slab: Introduce kmalloc_size_roundup() | expand

Commit Message

Kees Cook Sept. 23, 2022, 8:28 p.m. UTC 
Instead of discovering the kmalloc bucket size _after_ allocation, round
up proactively so the allocation is explicitly made for the full size,
allowing the compiler to correctly reason about the resulting size of
the buffer through the existing __alloc_size() hint.

Cc: Chris Mason <clm@fb.com>
Cc: Josef Bacik <josef@toxicpanda.com>
Cc: linux-btrfs@vger.kernel.org
Acked-by: David Sterba <dsterba@suse.com>
Link: https://lore.kernel.org/lkml/20220922133014.GI32411@suse.cz
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 fs/btrfs/send.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)
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Patch

diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
index e7671afcee4f..d40d65598e8f 100644
--- a/fs/btrfs/send.c
+++ b/fs/btrfs/send.c
@@ -435,6 +435,11 @@  static int fs_path_ensure_buf(struct fs_path *p, int len)
 	path_len = p->end - p->start;
 	old_buf_len = p->buf_len;
 
+	/*
+	 * Allocate to the next largest kmalloc bucket size, to let
+	 * the fast path happen most of the time.
+	 */
+	len = kmalloc_size_roundup(len);
 	/*
 	 * First time the inline_buf does not suffice
 	 */
@@ -448,11 +453,7 @@  static int fs_path_ensure_buf(struct fs_path *p, int len)
 	if (!tmp_buf)
 		return -ENOMEM;
 	p->buf = tmp_buf;
-	/*
-	 * The real size of the buffer is bigger, this will let the fast path
-	 * happen most of the time
-	 */
-	p->buf_len = ksize(p->buf);
+	p->buf_len = len;
 
 	if (p->reversed) {
 		tmp_buf = p->buf + old_buf_len - path_len - 1;