On 06/04, Eric Biggers wrote:
> On Mon, May 18, 2020 at 12:10:16PM -0700, Jaegeuk Kim wrote:
> > 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 <ebigg...@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 <ebigg...@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.
> >
>
> I went through every remaining caller of f2fs_kmalloc() and f2fs_kzalloc(). I
> think we're fine, except for possibly the allocation of blkz_seq in
> init_blkz_info(). How many zones can we expect on a zoned block device?
In the worst case, it can be 16TB / 2MB = 8M entries.
>
> Other than that, the largest fixed-size allocation is 8536 bytes
> (struct discard_cmd_control). And the variable-size allocations are all a
> page
> or less, except for xattr buffers which maybe can be larger, but the VFS uses
> kmalloc() for those too.
>
> Anyway, f2fs used to allocate megabytes with kmalloc(), so I'm not surprised
> you
> had issues before. But that's not a good reason to make *every* caller
> potentially get vmalloc()'ed memory, in the process introducing bugs where
> vmalloc() memory isn't handled correctly.
Thank you for checking all the cases. Let me know, if this is the final version.
I may be able to merge and try to see if somebody will complain later. :P
Thanks,
>
> - Eric
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