jbd2: avoid dozens of -Wflex-array-member-not-at-end warnings

-Wflex-array-member-not-at-end was introduced in GCC-14, and we
are getting ready to enable it, globally.

Use the `DEFINE_RAW_FLEX()` helper for an on-stack definition of
a flexible structure (`struct shash_desc`) where the size of the
flexible-array member (`__ctx`) is known at compile-time, and
refactor the rest of the code, accordingly.

So, with this, fix 77 of the following warnings:

include/linux/jbd2.h:1800:35: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://patch.msgid.link/ZyU94w0IALVhc9Jy@kspp
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
index 8aef9bb6ad573518d6f8e0fa76af8530db02b2e8..50f7ea8714bf46cee88b543d35427ef4541f7538 100644 (file)
--- a/include/linux/jbd2.h
+++ b/include/linux/jbd2.h
@@ -1796,22 +1796,21 @@ static inline unsigned long jbd2_log_space_left(journal_t *journal)
 static inline u32 jbd2_chksum(journal_t *journal, u32 crc,
                              const void *address, unsigned int length)
 {
-       struct {
-               struct shash_desc shash;
-               char ctx[JBD_MAX_CHECKSUM_SIZE];
-       } desc;
+       DEFINE_RAW_FLEX(struct shash_desc, desc, __ctx,
+               DIV_ROUND_UP(JBD_MAX_CHECKSUM_SIZE,
+                            sizeof(*((struct shash_desc *)0)->__ctx)));
        int err;
 
        BUG_ON(crypto_shash_descsize(journal->j_chksum_driver) >
                JBD_MAX_CHECKSUM_SIZE);
 
-       desc.shash.tfm = journal->j_chksum_driver;
-       *(u32 *)desc.ctx = crc;
+       desc->tfm = journal->j_chksum_driver;
+       *(u32 *)desc->__ctx = crc;
 
-       err = crypto_shash_update(&desc.shash, address, length);
+       err = crypto_shash_update(desc, address, length);
        BUG_ON(err);
 
-       return *(u32 *)desc.ctx;
+       return *(u32 *)desc->__ctx;
 }
 
 /* Return most recent uncommitted transaction */