| Message ID | 20211005093406.1241222-1-geert@linux-m68k.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [-next] btrfs: lzo: Mask instead of divide to fix 32-bit build | expand |
On 2021/10/5 17:34, Geert Uytterhoeven wrote: > On 32-bit builds (e.g. m68k): > > ERROR: modpost: "__umoddi3" [fs/btrfs/btrfs.ko] undefined! > > "cur_in - start" is 64-bit, while sectorsize is u32. > > As sectorsize is always a power of two, the 64-by-32 modulo operation > can be replaced by a much cheaper bitwise AND with "sectorsize - 1". > > Fixes: 0078783c7089fc83 ("btrfs: rework lzo_compress_pages() to make it subpage compatible") > Reported-by: noreply@ellerman.id.au > Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org> Oh, thanks for catching this. Reviewed-by: Qu Wenruo <wqu@suse.com> Thanks, Qu > --- > Compile-tested only. > --- > fs/btrfs/lzo.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/fs/btrfs/lzo.c b/fs/btrfs/lzo.c > index 47003cec4046f13e..d08f9eba49dab3cd 100644 > --- a/fs/btrfs/lzo.c > +++ b/fs/btrfs/lzo.c > @@ -211,7 +211,7 @@ int lzo_compress_pages(struct list_head *ws, struct address_space *mapping, > */ > cur_out += LZO_LEN; > while (cur_in < start + len) { > - u32 sector_off = (cur_in - start) % sectorsize; > + u32 sector_off = (cur_in - start) & (sectorsize - 1); > u32 in_len; > size_t out_len; > >
On Tue, Oct 05, 2021 at 11:34:06AM +0200, Geert Uytterhoeven wrote: > On 32-bit builds (e.g. m68k): > > ERROR: modpost: "__umoddi3" [fs/btrfs/btrfs.ko] undefined! > > "cur_in - start" is 64-bit, while sectorsize is u32. > > As sectorsize is always a power of two, the 64-by-32 modulo operation > can be replaced by a much cheaper bitwise AND with "sectorsize - 1". > > Fixes: 0078783c7089fc83 ("btrfs: rework lzo_compress_pages() to make it subpage compatible") > Reported-by: noreply@ellerman.id.au > Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org> Thanks. Folded to the patch as it's still in the devel queue.
diff --git a/fs/btrfs/lzo.c b/fs/btrfs/lzo.c index 47003cec4046f13e..d08f9eba49dab3cd 100644 --- a/fs/btrfs/lzo.c +++ b/fs/btrfs/lzo.c @@ -211,7 +211,7 @@ int lzo_compress_pages(struct list_head *ws, struct address_space *mapping, */ cur_out += LZO_LEN; while (cur_in < start + len) { - u32 sector_off = (cur_in - start) % sectorsize; + u32 sector_off = (cur_in - start) & (sectorsize - 1); u32 in_len; size_t out_len;
On 32-bit builds (e.g. m68k): ERROR: modpost: "__umoddi3" [fs/btrfs/btrfs.ko] undefined! "cur_in - start" is 64-bit, while sectorsize is u32. As sectorsize is always a power of two, the 64-by-32 modulo operation can be replaced by a much cheaper bitwise AND with "sectorsize - 1". Fixes: 0078783c7089fc83 ("btrfs: rework lzo_compress_pages() to make it subpage compatible") Reported-by: noreply@ellerman.id.au Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org> --- Compile-tested only. --- fs/btrfs/lzo.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)