| Message ID | 1457714093-21926-4-git-send-email-hch@lst.de (mailing list archive) |
|---|---|
| State | Accepted, archived |
| Delegated to: | Jens Axboe |
| Headers | show |
On Fri, Mar 11, 2016 at 05:34:52PM +0100, Christoph Hellwig wrote: > Replace the while loop that unecessarily checks for a NULL bio in the fast > path witch a simple goto loop. s/witch/with/ ? > > Signed-off-by: Christoph Hellwig <hch@lst.de> > --- > block/bio.c | 35 +++++++++++++++++------------------ > 1 file changed, 17 insertions(+), 18 deletions(-) > > diff --git a/block/bio.c b/block/bio.c > index 67e51ac..e4682ec 100644 > --- a/block/bio.c > +++ b/block/bio.c > @@ -1745,26 +1745,25 @@ static inline bool bio_remaining_done(struct bio *bio) > **/ > void bio_endio(struct bio *bio) > { > - while (bio) { > - if (unlikely(!bio_remaining_done(bio))) > - break; > +again: > + if (unlikely(!bio_remaining_done(bio))) > + return; > > - /* > - * Need to have a real endio function for chained bios, > - * otherwise various corner cases will break (like stacking > - * block devices that save/restore bi_end_io) - however, we want > - * to avoid unbounded recursion and blowing the stack. Tail call > - * optimization would handle this, but compiling with frame > - * pointers also disables gcc's sibling call optimization. > - */ > - if (bio->bi_end_io == bio_chain_endio) { > - bio = __bio_chain_endio(bio); > - } else { > - if (bio->bi_end_io) > - bio->bi_end_io(bio); > - bio = NULL; > - } > + /* > + * Need to have a real endio function for chained bios, otherwise > + * various corner cases will break (like stacking block devices that > + * save/restore bi_end_io) - however, we want to avoid unbounded > + * recursion and blowing the stack. Tail call optimization would > + * handle this, but compiling with frame pointers also disables > + * gcc's sibling call optimization. > + */ > + if (bio->bi_end_io == bio_chain_endio) { > + bio = __bio_chain_endio(bio); > + goto again; > } > + > + if (bio->bi_end_io) > + bio->bi_end_io(bio); > } > EXPORT_SYMBOL(bio_endio); > > -- > 2.1.4 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-block" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html Just out of curiosity, do you have any numbers for this change?
Looks fine,
Reviewed-by: Sagi Grimberg <sagig@mellanox.com>
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diff --git a/block/bio.c b/block/bio.c index 67e51ac..e4682ec 100644 --- a/block/bio.c +++ b/block/bio.c @@ -1745,26 +1745,25 @@ static inline bool bio_remaining_done(struct bio *bio) **/ void bio_endio(struct bio *bio) { - while (bio) { - if (unlikely(!bio_remaining_done(bio))) - break; +again: + if (unlikely(!bio_remaining_done(bio))) + return; - /* - * Need to have a real endio function for chained bios, - * otherwise various corner cases will break (like stacking - * block devices that save/restore bi_end_io) - however, we want - * to avoid unbounded recursion and blowing the stack. Tail call - * optimization would handle this, but compiling with frame - * pointers also disables gcc's sibling call optimization. - */ - if (bio->bi_end_io == bio_chain_endio) { - bio = __bio_chain_endio(bio); - } else { - if (bio->bi_end_io) - bio->bi_end_io(bio); - bio = NULL; - } + /* + * Need to have a real endio function for chained bios, otherwise + * various corner cases will break (like stacking block devices that + * save/restore bi_end_io) - however, we want to avoid unbounded + * recursion and blowing the stack. Tail call optimization would + * handle this, but compiling with frame pointers also disables + * gcc's sibling call optimization. + */ + if (bio->bi_end_io == bio_chain_endio) { + bio = __bio_chain_endio(bio); + goto again; } + + if (bio->bi_end_io) + bio->bi_end_io(bio); } EXPORT_SYMBOL(bio_endio);
Replace the while loop that unecessarily checks for a NULL bio in the fast path witch a simple goto loop. Signed-off-by: Christoph Hellwig <hch@lst.de> --- block/bio.c | 35 +++++++++++++++++------------------ 1 file changed, 17 insertions(+), 18 deletions(-)