Messages in this thread | | | From | Dan Streetman <> | Date | Fri, 25 Nov 2016 10:59:56 -0500 | Subject | Re: [PATCH 2/3] z3fold: don't fail kernel build if z3fold_header is too big |
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On Tue, Nov 15, 2016 at 11:00 AM, Vitaly Wool <vitalywool@gmail.com> wrote: > Currently the whole kernel build will be stopped if the size of > struct z3fold_header is greater than the size of one chunk, which > is 64 bytes by default. This may stand in the way of automated > test/debug builds so let's remove that and just fail the z3fold > initialization in such case instead. > > Signed-off-by: Vitaly Wool <vitalywool@gmail.com> > --- > mm/z3fold.c | 11 ++++++++--- > 1 file changed, 8 insertions(+), 3 deletions(-) > > diff --git a/mm/z3fold.c b/mm/z3fold.c > index 7ad70fa..ffd9353 100644 > --- a/mm/z3fold.c > +++ b/mm/z3fold.c > @@ -870,10 +870,15 @@ MODULE_ALIAS("zpool-z3fold"); > > static int __init init_z3fold(void) > { > - /* Make sure the z3fold header will fit in one chunk */ > - BUILD_BUG_ON(sizeof(struct z3fold_header) > ZHDR_SIZE_ALIGNED);
Nak. this is the wrong way to handle this. The build bug is there to indicate to you that your patch makes the header too large, not as a runtime check to disable everything.
The right way to handle it is to change the hardcoded assumption that the header fits into a single chunk; e.g.:
#define ZHDR_SIZE_ALIGNED round_up(sizeof(struct z3fold_header), CHUNK_SIZE) #define ZHDR_CHUNKS (ZHDR_SIZE_ALIGNED >> CHUNK_SHIFT)
then use ZHDR_CHUNKS in all places where it's currently assumed the header is 1 chunk, e.g. in num_free_chunks:
if (zhdr->middle_chunks != 0) { int nfree_before = zhdr->first_chunks ? - 0 : zhdr->start_middle - 1; + 0 : zhdr->start_middle - ZHDR_CHUNKS;
after changing all needed places like that, the build bug isn't needed anymore (unless we want to make sure the header isn't larger than some arbitrary number N chunks)
> - zpool_register_driver(&z3fold_zpool_driver); > + /* Fail the initialization if z3fold header won't fit in one chunk */ > + if (sizeof(struct z3fold_header) > ZHDR_SIZE_ALIGNED) { > + pr_err("z3fold: z3fold_header size (%d) is bigger than " > + "the chunk size (%d), can't proceed\n", > + sizeof(struct z3fold_header) , ZHDR_SIZE_ALIGNED); > + return -E2BIG; > + } > > + zpool_register_driver(&z3fold_zpool_driver); > return 0; > } > > -- > 2.4.2
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