On Mon, May 27, 2024 at 2:21 AM Sasha Levin wrote: > > This is a note to let you know that I've just added the patch titled > > nilfs2: make superblock data array index computation sparse friendly > > to the 6.9-stable tree which can be found at: > http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary > > The filename of the patch is: > nilfs2-make-superblock-data-array-index-computation-.patch > and it can be found in the queue-6.9 subdirectory. > > If you, or anyone else, feels it should not be added to the stable tree, > please let <stable@xxxxxxxxxxxxxxx> know about it. > > > > commit 5017482ff3b29550015cce7f81279dc69aefd6fe > Author: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxx> > Date: Tue Apr 30 17:00:19 2024 +0900 > > nilfs2: make superblock data array index computation sparse friendly > > [ 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@xxxxxxxxx > Fixes: e339ad31f599 ("nilfs2: introduce secondary super block") > Signed-off-by: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxx> > Cc: Bart Van Assche <bvanassche@xxxxxxx> > Cc: Jens Axboe <axboe@xxxxxxxxx> > Cc: kernel test robot <lkp@xxxxxxxxx> > Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> > > 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; > } This commit fixes the sparse warning output by build "make C=1" with the sparse check, but does not fix any operational bugs. Therefore, if fixing a harmless sparse warning does not meet the requirements for backporting to stable trees (I assume it does), please drop it as it is a false positive pickup. Sorry if the "Fixes:" tag is confusing. The same goes for the same patch queued to other stable-trees. Thanks, Ryusuke Konishi
