From: Jens Axboe axboe@kernel.dk
stable inclusion from stable-v6.6.5 commit 9e1152a6c2b5488b688f50f81a6af029b2537258 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I8N21P
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...
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commit b10b73c102a2eab91e1cd62a03d6446f1dfecc64 upstream.
Right now we stash any potentially mmap'ed provided ring buffer range for freeing at release time, regardless of when they get unregistered. Since we're keeping track of these ranges anyway, keep track of their registration state as well, and use that to recycle ranges when appropriate rather than always allocate new ones.
The lookup is a basic scan of entries, checking for the best matching free entry.
Fixes: c392cbecd8ec ("io_uring/kbuf: defer release of mapped buffer rings") Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Zheng Zengkai zhengzengkai@huawei.com --- io_uring/kbuf.c | 77 ++++++++++++++++++++++++++++++++++++++++++------- 1 file changed, 66 insertions(+), 11 deletions(-)
diff --git a/io_uring/kbuf.c b/io_uring/kbuf.c index 8da5c10ec352..012f62203604 100644 --- a/io_uring/kbuf.c +++ b/io_uring/kbuf.c @@ -44,6 +44,8 @@ static struct io_buffer_list *__io_buffer_get_list(struct io_ring_ctx *ctx, struct io_buf_free { struct hlist_node list; void *mem; + size_t size; + int inuse; };
static inline struct io_buffer_list *io_buffer_get_list(struct io_ring_ctx *ctx, @@ -231,6 +233,24 @@ static __cold int io_init_bl_list(struct io_ring_ctx *ctx) return 0; }
+/* + * Mark the given mapped range as free for reuse + */ +static void io_kbuf_mark_free(struct io_ring_ctx *ctx, struct io_buffer_list *bl) +{ + struct io_buf_free *ibf; + + hlist_for_each_entry(ibf, &ctx->io_buf_list, list) { + if (bl->buf_ring == ibf->mem) { + ibf->inuse = 0; + return; + } + } + + /* can't happen... */ + WARN_ON_ONCE(1); +} + static int __io_remove_buffers(struct io_ring_ctx *ctx, struct io_buffer_list *bl, unsigned nbufs) { @@ -247,6 +267,7 @@ static int __io_remove_buffers(struct io_ring_ctx *ctx, * io_kbuf_list_free() will free the page(s) at * ->release() time. */ + io_kbuf_mark_free(ctx, bl); bl->buf_ring = NULL; bl->is_mmap = 0; } else if (bl->buf_nr_pages) { @@ -560,6 +581,34 @@ static int io_pin_pbuf_ring(struct io_uring_buf_reg *reg, return -EINVAL; }
+/* + * See if we have a suitable region that we can reuse, rather than allocate + * both a new io_buf_free and mem region again. We leave it on the list as + * even a reused entry will need freeing at ring release. + */ +static struct io_buf_free *io_lookup_buf_free_entry(struct io_ring_ctx *ctx, + size_t ring_size) +{ + struct io_buf_free *ibf, *best = NULL; + size_t best_dist; + + hlist_for_each_entry(ibf, &ctx->io_buf_list, list) { + size_t dist; + + if (ibf->inuse || ibf->size < ring_size) + continue; + dist = ibf->size - ring_size; + if (!best || dist < best_dist) { + best = ibf; + if (!dist) + break; + best_dist = dist; + } + } + + return best; +} + static int io_alloc_pbuf_ring(struct io_ring_ctx *ctx, struct io_uring_buf_reg *reg, struct io_buffer_list *bl) @@ -569,20 +618,26 @@ static int io_alloc_pbuf_ring(struct io_ring_ctx *ctx, void *ptr;
ring_size = reg->ring_entries * sizeof(struct io_uring_buf_ring); - ptr = io_mem_alloc(ring_size); - if (!ptr) - return -ENOMEM;
- /* Allocate and store deferred free entry */ - ibf = kmalloc(sizeof(*ibf), GFP_KERNEL_ACCOUNT); + /* Reuse existing entry, if we can */ + ibf = io_lookup_buf_free_entry(ctx, ring_size); if (!ibf) { - io_mem_free(ptr); - return -ENOMEM; - } - ibf->mem = ptr; - hlist_add_head(&ibf->list, &ctx->io_buf_list); + ptr = io_mem_alloc(ring_size); + if (!ptr) + return -ENOMEM;
- bl->buf_ring = ptr; + /* Allocate and store deferred free entry */ + ibf = kmalloc(sizeof(*ibf), GFP_KERNEL_ACCOUNT); + if (!ibf) { + io_mem_free(ptr); + return -ENOMEM; + } + ibf->mem = ptr; + ibf->size = ring_size; + hlist_add_head(&ibf->list, &ctx->io_buf_list); + } + ibf->inuse = 1; + bl->buf_ring = ibf->mem; bl->is_mapped = 1; bl->is_mmap = 1; return 0;