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

This reverts commit 5a519c8fe4d620912385f94372fc8472fa98c662.

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>

diff --git a/fs/pipe.c b/fs/pipe.c
index 9648ac1..e140ea1 100644 (file)
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -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)