[PATCH] btrfs: scrub: remove impossible sanity checks

[PATCH] btrfs: scrub: remove impossible sanity checks

[Qu Wenruo]

There are several sanity checks which are no longer possible to trigger
inside btrfs_scrub_dev().

Since we have mount time check against super block nodesize/sectorsize,
and our fixed macro is hardcoded to handle even the worst combination.

Thus those sanity checks are no longer needed, can be easily removed.

But this patch still uses some ASSERT()s as a safe net just in case we
change some features in the future to trigger those impossible
combinations.

Signed-off-by: Qu Wenruo <wqu@suse.com>
---
 fs/btrfs/scrub.c | 34 +++++++++-------------------------
 1 file changed, 9 insertions(+), 25 deletions(-)

diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index d05025034b0a..c4e030661fac 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -4096,32 +4096,16 @@ int btrfs_scrub_dev(struct btrfs_fs_info *fs_info, u64 devid, u64 start,
 	if (btrfs_fs_closing(fs_info))
 		return -EAGAIN;
 
-	if (fs_info->nodesize > BTRFS_STRIPE_LEN) {
-		/*
-		 * in this case scrub is unable to calculate the checksum
-		 * the way scrub is implemented. Do not handle this
-		 * situation at all because it won't ever happen.
-		 */
-		btrfs_err(fs_info,
-			   "scrub: size assumption nodesize <= BTRFS_STRIPE_LEN (%d <= %d) fails",
-		       fs_info->nodesize,
-		       BTRFS_STRIPE_LEN);
-		return -EINVAL;
-	}
+	/* At mount time we have ensured nodesize is in the range of [4K, 64K]. */
+	ASSERT(fs_info->nodesize <= BTRFS_STRIPE_LEN);
 
-	if (fs_info->nodesize >
-	    SCRUB_MAX_SECTORS_PER_BLOCK << fs_info->sectorsize_bits ||
-	    fs_info->sectorsize > PAGE_SIZE * SCRUB_MAX_SECTORS_PER_BLOCK) {
-		/*
-		 * Would exhaust the array bounds of sectorv member in
-		 * struct scrub_block
-		 */
-		btrfs_err(fs_info,
-"scrub: nodesize and sectorsize <= SCRUB_MAX_SECTORS_PER_BLOCK (%d <= %d && %d <= %d) fails",
-		       fs_info->nodesize, SCRUB_MAX_SECTORS_PER_BLOCK,
-		       fs_info->sectorsize, SCRUB_MAX_SECTORS_PER_BLOCK);
-		return -EINVAL;
-	}
+	/*
+	 * SCRUB_MAX_SECTORS_PER_BLOCK is calculated using the largest possible
+	 * value (max nodesize / min sectorsize), thus nodesize should always
+	 * be fine.
+	 */
+	ASSERT(fs_info->nodesize <=
+	       SCRUB_MAX_SECTORS_PER_BLOCK << fs_info->sectorsize_bits);
 
 	/* Allocate outside of device_list_mutex */
 	sctx = scrub_setup_ctx(fs_info, is_dev_replace);
-- 
2.37.0

Re: [PATCH] btrfs: scrub: remove impossible sanity checks

[David Sterba]

On Wed, Aug 10, 2022 at 01:58:57PM +0800, Qu Wenruo wrote:
> There are several sanity checks which are no longer possible to trigger
> inside btrfs_scrub_dev().
> 
> Since we have mount time check against super block nodesize/sectorsize,
> and our fixed macro is hardcoded to handle even the worst combination.
> 
> Thus those sanity checks are no longer needed, can be easily removed.
> 
> But this patch still uses some ASSERT()s as a safe net just in case we
> change some features in the future to trigger those impossible
> combinations.
> 
> Signed-off-by: Qu Wenruo <wqu@suse.com>

Added to misc-next, thanks.