| From: Ryusuke Konishi <konishi.ryusuke@gmail.com> |
| Subject: nilfs2: make superblock data array index computation sparse friendly |
| Date: Tue, 30 Apr 2024 17:00:19 +0900 |
| |
| Upon running sparse, "warning: dubious: x & !y" is output at an array |
| index calculation within nilfs_load_super_block(). |
| |
| The calculation is not wrong, but to eliminate the sparse warning, replace |
| it with an equivalent calculation. |
| |
| Also, add a comment to make it easier to understand what the unintuitive |
| array index calculation is doing and whether it's correct. |
| |
| Link: https://lkml.kernel.org/r/20240430080019.4242-3-konishi.ryusuke@gmail.com |
| Fixes: e339ad31f599 ("nilfs2: introduce secondary super block") |
| Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com> |
| Cc: Bart Van Assche <bvanassche@acm.org> |
| Cc: Jens Axboe <axboe@kernel.dk> |
| Cc: kernel test robot <lkp@intel.com> |
| Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
| --- |
| |
| fs/nilfs2/the_nilfs.c | 20 ++++++++++++++++++-- |
| 1 file changed, 18 insertions(+), 2 deletions(-) |
| |
| --- a/fs/nilfs2/the_nilfs.c~nilfs2-make-superblock-data-array-index-computation-sparse-friendly |
| +++ a/fs/nilfs2/the_nilfs.c |
| @@ -592,7 +592,7 @@ static int nilfs_load_super_block(struct |
| struct nilfs_super_block **sbp = nilfs->ns_sbp; |
| struct buffer_head **sbh = nilfs->ns_sbh; |
| u64 sb2off, devsize = bdev_nr_bytes(nilfs->ns_bdev); |
| - int valid[2], swp = 0; |
| + int valid[2], swp = 0, older; |
| |
| if (devsize < NILFS_SEG_MIN_BLOCKS * NILFS_MIN_BLOCK_SIZE + 4096) { |
| nilfs_err(sb, "device size too small"); |
| @@ -648,9 +648,25 @@ static int nilfs_load_super_block(struct |
| if (swp) |
| nilfs_swap_super_block(nilfs); |
| |
| + /* |
| + * Calculate the array index of the older superblock data. |
| + * If one has been dropped, set index 0 pointing to the remaining one, |
| + * otherwise set index 1 pointing to the old one (including if both |
| + * are the same). |
| + * |
| + * Divided case valid[0] valid[1] swp -> older |
| + * ------------------------------------------------------------- |
| + * Both SBs are invalid 0 0 N/A (Error) |
| + * SB1 is invalid 0 1 1 0 |
| + * SB2 is invalid 1 0 0 0 |
| + * SB2 is newer 1 1 1 0 |
| + * SB2 is older or the same 1 1 0 1 |
| + */ |
| + older = valid[1] ^ swp; |
| + |
| nilfs->ns_sbwcount = 0; |
| nilfs->ns_sbwtime = le64_to_cpu(sbp[0]->s_wtime); |
| - nilfs->ns_prot_seq = le64_to_cpu(sbp[valid[1] & !swp]->s_last_seq); |
| + nilfs->ns_prot_seq = le64_to_cpu(sbp[older]->s_last_seq); |
| *sbpp = sbp[0]; |
| return 0; |
| } |
| _ |
