6.9-stable review patch. If anyone has any objections, please let me know.
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From: Ryusuke Konishi konishi.ryusuke@gmail.com
[ Upstream commit 91d743a9c8299de1fc1b47428d8bb4c85face00f ]
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 Signed-off-by: Sasha Levin sashal@kernel.org --- fs/nilfs2/the_nilfs.c | 20 ++++++++++++++++++-- 1 file changed, 18 insertions(+), 2 deletions(-)
diff --git a/fs/nilfs2/the_nilfs.c b/fs/nilfs2/the_nilfs.c index 2ae2c1bbf6d17..adbc6e87471ab 100644 --- a/fs/nilfs2/the_nilfs.c +++ b/fs/nilfs2/the_nilfs.c @@ -592,7 +592,7 @@ static int nilfs_load_super_block(struct the_nilfs *nilfs, 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 the_nilfs *nilfs, 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; }