Re: [f2fs-dev] [PATCH] f2fs: don't return vmalloc() memory from f2fs_kmalloc()

[Jaegeuk Kim <jaegeuk@kernel.org>]

On 05/18, Eric Biggers wrote:
> On Mon, May 18, 2020 at 11:06:48AM -0700, Jaegeuk Kim wrote:
> > On 05/05, Eric Biggers wrote:
> > > From: Eric Biggers <ebiggers@google.com>
> > > 
> > > kmalloc() returns kmalloc'ed memory, and kvmalloc() returns either
> > > kmalloc'ed or vmalloc'ed memory.  But the f2fs wrappers, f2fs_kmalloc()
> > > and f2fs_kvmalloc(), both return both kinds of memory.
> > > 
> > > It's redundant to have two functions that do the same thing, and also
> > > breaking the standard naming convention is causing bugs since people
> > > assume it's safe to kfree() memory allocated by f2fs_kmalloc().  See
> > > e.g. the various allocations in fs/f2fs/compress.c.
> > > 
> > > Fix this by making f2fs_kmalloc() just use kmalloc().  And to avoid
> > > re-introducing the allocation failures that the vmalloc fallback was
> > > intended to fix, convert the largest allocations to use f2fs_kvmalloc().
> > > 
> > > Signed-off-by: Eric Biggers <ebiggers@google.com>
> > > ---
> > >  fs/f2fs/checkpoint.c | 4 ++--
> > >  fs/f2fs/f2fs.h       | 8 +-------
> > >  fs/f2fs/node.c       | 8 ++++----
> > >  3 files changed, 7 insertions(+), 13 deletions(-)
> > > 
> > > diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
> > > index 97b6378554b406..ac5b47f15f5e77 100644
> > > --- a/fs/f2fs/checkpoint.c
> > > +++ b/fs/f2fs/checkpoint.c
> > > @@ -895,8 +895,8 @@ int f2fs_get_valid_checkpoint(struct f2fs_sb_info *sbi)
> > >  	int i;
> > >  	int err;
> > >  
> > > -	sbi->ckpt = f2fs_kzalloc(sbi, array_size(blk_size, cp_blks),
> > > -				 GFP_KERNEL);
> > > +	sbi->ckpt = f2fs_kvzalloc(sbi, array_size(blk_size, cp_blks),
> > > +				  GFP_KERNEL);
> > >  	if (!sbi->ckpt)
> > >  		return -ENOMEM;
> > >  	/*
> > > diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> > > index d036a31a97e84e..bc4c5b9b1bf14c 100644
> > > --- a/fs/f2fs/f2fs.h
> > > +++ b/fs/f2fs/f2fs.h
> > > @@ -2953,18 +2953,12 @@ static inline bool f2fs_may_extent_tree(struct inode *inode)
> > >  static inline void *f2fs_kmalloc(struct f2fs_sb_info *sbi,
> > >  					size_t size, gfp_t flags)
> > >  {
> > > -	void *ret;
> > > -
> > >  	if (time_to_inject(sbi, FAULT_KMALLOC)) {
> > >  		f2fs_show_injection_info(sbi, FAULT_KMALLOC);
> > >  		return NULL;
> > >  	}
> > >  
> > > -	ret = kmalloc(size, flags);
> > > -	if (ret)
> > > -		return ret;
> > > -
> > > -	return kvmalloc(size, flags);
> > > +	return kmalloc(size, flags);
> > 
> > IIRC, sometimes, we suffered from ENOMEM from kmalloc, as some structures
> > depended on the disk capacity. I can't remember exactly which structure tho.
> > 
> 
> I think this patch already addresses that, by changing the large allocations to
> use f2fs_kvmalloc().

Hmm, I worried a bit whether it covers every cases.

> 
> - Eric


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