On Thu, Aug 20, 2015 at 05:08:24PM +0800, Chao Yu wrote: > Hi Jaegeuk, > > > -----Original Message----- > > From: Jaegeuk Kim [mailto:jaegeuk@xxxxxxxxxx] > > Sent: Saturday, August 15, 2015 7:09 AM > > To: linux-kernel@xxxxxxxxxxxxxxx; linux-fsdevel@xxxxxxxxxxxxxxx; > > linux-f2fs-devel@xxxxxxxxxxxxxxxxxxxxx > > Cc: Jaegeuk Kim > > Subject: [f2fs-dev] [PATCH 1/2] f2fs: handle failed bio allocation > > > > As the below comment of bio_alloc_bioset, f2fs can allocate multiple bios at the > > same time. So, we can't guarantee that bio is allocated all the time. > > > > " > > * When @bs is not NULL, if %__GFP_WAIT is set then bio_alloc will always be > > * able to allocate a bio. This is due to the mempool guarantees. To make this > > * work, callers must never allocate more than 1 bio at a time from this pool. > > * Callers that need to allocate more than 1 bio must always submit the > > * previously allocated bio for IO before attempting to allocate a new one. > > * Failure to do so can cause deadlocks under memory pressure. > > " > > > > Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx> > > --- > > fs/f2fs/data.c | 3 +-- > > fs/f2fs/f2fs.h | 15 +++++++++++++++ > > fs/f2fs/segment.c | 14 +++++++++++--- > > 3 files changed, 27 insertions(+), 5 deletions(-) > > > > diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c > > index cad9ebe..726e58b 100644 > > --- a/fs/f2fs/data.c > > +++ b/fs/f2fs/data.c > > @@ -90,8 +90,7 @@ static struct bio *__bio_alloc(struct f2fs_sb_info *sbi, block_t blk_addr, > > { > > struct bio *bio; > > > > - /* No failure on bio allocation */ > > - bio = bio_alloc(GFP_NOIO, npages); > > How about using __GFP_NOFAIL flag to avoid failing in bio_alloc instead > of adding opencode endless loop in code? > > We can see the reason in this commit 647757197cd3 > ("mm: clarify __GFP_NOFAIL deprecation status ") > > "__GFP_NOFAIL is documented as a deprecated flag since commit > 478352e789f5 ("mm: add comment about deprecation of __GFP_NOFAIL"). > > This has discouraged people from using it but in some cases an opencoded > endless loop around allocator has been used instead. So the allocator > is not aware of the de facto __GFP_NOFAIL allocation because this > information was not communicated properly. > > Let's make clear that if the allocation context really cannot afford > failure because there is no good failure policy then using __GFP_NOFAIL > is preferable to opencoding the loop outside of the allocator." > > BTW, I found that f2fs_kmem_cache_alloc also could be replaced, we could > fix them together. Agreed. I think that can be another patch like this. >From 1579e0d1ada96994c4ec6619fb5b5d9386e77ab3 Mon Sep 17 00:00:00 2001 From: Jaegeuk Kim <jaegeuk@xxxxxxxxxx> Date: Thu, 20 Aug 2015 08:51:56 -0700 Subject: [PATCH] f2fs: use __GFP_NOFAIL to avoid infinite loop __GFP_NOFAIL can avoid retrying the whole path of kmem_cache_alloc and bio_alloc. Suggested-by: Chao Yu <chao2.yu@xxxxxxxxxxx> Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx> --- fs/f2fs/f2fs.h | 16 +++++----------- 1 file changed, 5 insertions(+), 11 deletions(-) diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h index 00591f7..c78b599 100644 --- a/fs/f2fs/f2fs.h +++ b/fs/f2fs/f2fs.h @@ -1244,13 +1244,10 @@ static inline void *f2fs_kmem_cache_alloc(struct kmem_cache *cachep, gfp_t flags) { void *entry; -retry: - entry = kmem_cache_alloc(cachep, flags); - if (!entry) { - cond_resched(); - goto retry; - } + entry = kmem_cache_alloc(cachep, flags); + if (!entry) + entry = kmem_cache_alloc(cachep, flags | __GFP_NOFAIL); return entry; } @@ -1259,12 +1256,9 @@ static inline struct bio *f2fs_bio_alloc(int npages) struct bio *bio; /* No failure on bio allocation */ -retry: bio = bio_alloc(GFP_NOIO, npages); - if (!bio) { - cond_resched(); - goto retry; - } + if (!bio) + bio = bio_alloc(GFP_NOIO | __GFP_NOFAIL, npages); return bio; } -- 2.1.1 -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
