From 2a8a98673c13cb2a61a6476153acf8344adfa992 Mon Sep 17 00:00:00 2001 From: Mauricio Faria de Oliveira Date: Wed, 5 Jul 2017 10:53:16 -0300 Subject: [PATCH] fs: aio: fix the increment of aio-nr and counting against aio-max-nr Currently, aio-nr is incremented in steps of 'num_possible_cpus() * 8' for io_setup(nr_events, ..) with 'nr_events < num_possible_cpus() * 4': ioctx_alloc() ... nr_events = max(nr_events, num_possible_cpus() * 4); nr_events *= 2; ... ctx->max_reqs = nr_events; ... aio_nr += ctx->max_reqs; .... This limits the number of aio contexts actually available to much less than aio-max-nr, and is increasingly worse with greater number of CPUs. For example, with 64 CPUs, only 256 aio contexts are actually available (with aio-max-nr = 65536) because the increment is 512 in that scenario. Note: 65536 [max aio contexts] / (64*4*2) [increment per aio context] is 128, but make it 256 (double) as counting against 'aio-max-nr * 2': ioctx_alloc() ... if (aio_nr + nr_events > (aio_max_nr * 2UL) || ... goto err_ctx; ... This patch uses the original value of nr_events (from userspace) to increment aio-nr and count against aio-max-nr, which resolves those. Signed-off-by: Mauricio Faria de Oliveira Reported-by: Lekshmi C. Pillai Tested-by: Lekshmi C. Pillai Tested-by: Paul Nguyen Reviewed-by: Jeff Moyer Signed-off-by: Benjamin LaHaise --- fs/aio.c | 19 ++++++++++++------- 1 file changed, 12 insertions(+), 7 deletions(-) diff --git a/fs/aio.c b/fs/aio.c index dcad3a66748c..8f0127526299 100644 --- a/fs/aio.c +++ b/fs/aio.c @@ -441,10 +441,9 @@ static const struct address_space_operations aio_ctx_aops = { #endif }; -static int aio_setup_ring(struct kioctx *ctx) +static int aio_setup_ring(struct kioctx *ctx, unsigned int nr_events) { struct aio_ring *ring; - unsigned nr_events = ctx->max_reqs; struct mm_struct *mm = current->mm; unsigned long size, unused; int nr_pages; @@ -706,6 +705,12 @@ static struct kioctx *ioctx_alloc(unsigned nr_events) struct kioctx *ctx; int err = -ENOMEM; + /* + * Store the original nr_events -- what userspace passed to io_setup(), + * for counting against the global limit -- before it changes. + */ + unsigned int max_reqs = nr_events; + /* * We keep track of the number of available ringbuffer slots, to prevent * overflow (reqs_available), and we also use percpu counters for this. @@ -724,14 +729,14 @@ static struct kioctx *ioctx_alloc(unsigned nr_events) return ERR_PTR(-EINVAL); } - if (!nr_events || (unsigned long)nr_events > (aio_max_nr * 2UL)) + if (!nr_events || (unsigned long)max_reqs > aio_max_nr) return ERR_PTR(-EAGAIN); ctx = kmem_cache_zalloc(kioctx_cachep, GFP_KERNEL); if (!ctx) return ERR_PTR(-ENOMEM); - ctx->max_reqs = nr_events; + ctx->max_reqs = max_reqs; spin_lock_init(&ctx->ctx_lock); spin_lock_init(&ctx->completion_lock); @@ -753,7 +758,7 @@ static struct kioctx *ioctx_alloc(unsigned nr_events) if (!ctx->cpu) goto err; - err = aio_setup_ring(ctx); + err = aio_setup_ring(ctx, nr_events); if (err < 0) goto err; @@ -764,8 +769,8 @@ static struct kioctx *ioctx_alloc(unsigned nr_events) /* limit the number of system wide aios */ spin_lock(&aio_nr_lock); - if (aio_nr + nr_events > (aio_max_nr * 2UL) || - aio_nr + nr_events < aio_nr) { + if (aio_nr + ctx->max_reqs > aio_max_nr || + aio_nr + ctx->max_reqs < aio_nr) { spin_unlock(&aio_nr_lock); err = -EAGAIN; goto err_ctx; -- 2.30.2