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authorQu Wenruo <wqu@suse.com>2023-10-28 05:58:45 +0300
committerDavid Sterba <dsterba@suse.com>2023-11-03 18:40:15 +0300
commit47e2b06b7b5cb356a987ba3429550c3a89ea89d6 (patch)
treed1415f4cad3a193ec3a2259ee07d134ce7dbe62a /fs/btrfs/scrub.c
parentd8ba2a91fc3cd0347823435971f58f473cbba7aa (diff)
downloadlinux-47e2b06b7b5cb356a987ba3429550c3a89ea89d6.tar.xz
btrfs: make found_logical_ret parameter mandatory for function queue_scrub_stripe()
[BUG] There is a compilation warning reported on commit ae76d8e3e135 ("btrfs: scrub: fix grouping of read IO"), where gcc (14.0.0 20231022 experimental) is reporting the following uninitialized variable: fs/btrfs/scrub.c: In function ‘scrub_simple_mirror.isra’: fs/btrfs/scrub.c:2075:29: error: ‘found_logical’ may be used uninitialized [-Werror=maybe-uninitialized[https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html#index-Wmaybe-uninitialized]] 2075 | cur_logical = found_logical + BTRFS_STRIPE_LEN; fs/btrfs/scrub.c:2040:21: note: ‘found_logical’ was declared here 2040 | u64 found_logical; | ^~~~~~~~~~~~~ [CAUSE] This is a false alert, as @found_logical is passed as parameter @found_logical_ret of function queue_scrub_stripe(). As long as queue_scrub_stripe() returned 0, we would update @found_logical_ret. And if queue_scrub_stripe() returned >0 or <0, the caller would not utilized @found_logical, thus there should be nothing wrong. Although the triggering gcc is still experimental, it looks like the extra check on "if (found_logical_ret)" can sometimes confuse the compiler. Meanwhile the only caller of queue_scrub_stripe() is always passing a valid pointer, there is no need for such check at all. [FIX] Although the report itself is a false alert, we can still make it more explicit by: - Replace the check for @found_logical_ret with ASSERT() - Initialize @found_logical to U64_MAX - Add one extra ASSERT() to make sure @found_logical got updated Link: https://lore.kernel.org/linux-btrfs/87fs1x1p93.fsf@gentoo.org/ Fixes: ae76d8e3e135 ("btrfs: scrub: fix grouping of read IO") Reviewed-by: Anand Jain <anand.jain@oracle.com> Signed-off-by: Qu Wenruo <wqu@suse.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Diffstat (limited to 'fs/btrfs/scrub.c')
-rw-r--r--fs/btrfs/scrub.c10
1 files changed, 7 insertions, 3 deletions
diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index 9ce5be21b036..f62a408671cb 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -1868,6 +1868,9 @@ static int queue_scrub_stripe(struct scrub_ctx *sctx, struct btrfs_block_group *
*/
ASSERT(sctx->cur_stripe < SCRUB_TOTAL_STRIPES);
+ /* @found_logical_ret must be specified. */
+ ASSERT(found_logical_ret);
+
stripe = &sctx->stripes[sctx->cur_stripe];
scrub_reset_stripe(stripe);
ret = scrub_find_fill_first_stripe(bg, &sctx->extent_path,
@@ -1876,8 +1879,7 @@ static int queue_scrub_stripe(struct scrub_ctx *sctx, struct btrfs_block_group *
/* Either >0 as no more extents or <0 for error. */
if (ret)
return ret;
- if (found_logical_ret)
- *found_logical_ret = stripe->logical;
+ *found_logical_ret = stripe->logical;
sctx->cur_stripe++;
/* We filled one group, submit it. */
@@ -2080,7 +2082,7 @@ static int scrub_simple_mirror(struct scrub_ctx *sctx,
/* Go through each extent items inside the logical range */
while (cur_logical < logical_end) {
- u64 found_logical;
+ u64 found_logical = U64_MAX;
u64 cur_physical = physical + cur_logical - logical_start;
/* Canceled? */
@@ -2115,6 +2117,8 @@ static int scrub_simple_mirror(struct scrub_ctx *sctx,
if (ret < 0)
break;
+ /* queue_scrub_stripe() returned 0, @found_logical must be updated. */
+ ASSERT(found_logical != U64_MAX);
cur_logical = found_logical + BTRFS_STRIPE_LEN;
/* Don't hold CPU for too long time */