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Revert "fs/pipe: use kvcalloc to allocate a pipe_buffer array"

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This reverts commit 5a519c8fe4.

It turns out that making the pipe almost arbitrarily large has some
rather unexpected downsides.  The kernel test robot reports a kernel
warning that is due to pipe->max_usage now growing to the point where
the iter_file_splice_write() buffer allocation can no longer be
satisfied as a slab allocation, and the

        int nbufs = pipe->max_usage;
        struct bio_vec *array = kcalloc(nbufs, sizeof(struct bio_vec),
                                        GFP_KERNEL);

code sequence there will now always fail as a result.

That code could be modified to use kvcalloc() too, but I feel very
uncomfortable making those kinds of changes for a very niche use case
that really should have other options than make these kinds of
fundamental changes to pipe behavior.

Maybe the CRIU process dumping should be multi-threaded, and use
multiple pipes and multiple cores, rather than try to use one larger
pipe to minimize splice() calls.

Reported-by: kernel test robot <oliver.sang@intel.com>
Link: https://lore.kernel.org/all/20220420073717.GD16310@xsang-OptiPlex-9020/
Cc: Andrei Vagin <avagin@gmail.com>
Cc: Dmitry Safonov <0x7f454c46@gmail.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Linus Torvalds 2022-04-20 12:07:53 -07:00
parent a6823e4e36
commit 906f904097
1 changed files with 5 additions and 4 deletions
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9
fs/pipe.c
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@ -804,7 +804,7 @@ struct pipe_inode_info *alloc_pipe_info(void)
if (too_many_pipe_buffers_hard(user_bufs) && pipe_is_unprivileged_user())
goto out_revert_acct;
pipe->bufs = kvcalloc(pipe_bufs, sizeof(struct pipe_buffer),
pipe->bufs = kcalloc(pipe_bufs, sizeof(struct pipe_buffer),
GFP_KERNEL_ACCOUNT);
if (pipe->bufs) {
@ -849,7 +849,7 @@ void free_pipe_info(struct pipe_inode_info *pipe)
#endif
if (pipe->tmp_page)
__free_page(pipe->tmp_page);
kvfree(pipe->bufs);
kfree(pipe->bufs);
kfree(pipe);
}
@ -1264,7 +1264,8 @@ int pipe_resize_ring(struct pipe_inode_info *pipe, unsigned int nr_slots)
if (nr_slots < n)
return -EBUSY;
bufs = kvcalloc(nr_slots, sizeof(*bufs), GFP_KERNEL_ACCOUNT);
bufs = kcalloc(nr_slots, sizeof(*bufs),
GFP_KERNEL_ACCOUNT | __GFP_NOWARN);
if (unlikely(!bufs))
return -ENOMEM;
@ -1291,7 +1292,7 @@ int pipe_resize_ring(struct pipe_inode_info *pipe, unsigned int nr_slots)
head = n;
tail = 0;
kvfree(pipe->bufs);
kfree(pipe->bufs);
pipe->bufs = bufs;
pipe->ring_size = nr_slots;
if (pipe->max_usage > nr_slots)