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authorMauricio Faria de Oliveira <mauricfo@linux.vnet.ibm.com>2017-07-05 10:53:16 -0300
committerBenjamin LaHaise <bcrl@kvack.org>2017-09-07 12:28:28 -0400
commit2a8a98673c13cb2a61a6476153acf8344adfa992 (patch)
tree8d8234e781fcb78fdf6a9f5b8548f7cbbd0a0498 /fs/aio.c
parent569dbb88e80deb68974ef6fdd6a13edb9d686261 (diff)
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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 <mauricfo@linux.vnet.ibm.com> Reported-by: Lekshmi C. Pillai <lekshmi.cpillai@in.ibm.com> Tested-by: Lekshmi C. Pillai <lekshmi.cpillai@in.ibm.com> Tested-by: Paul Nguyen <nguyenp@us.ibm.com> Reviewed-by: Jeff Moyer <jmoyer@redhat.com> Signed-off-by: Benjamin LaHaise <bcrl@kvack.org>
Diffstat (limited to 'fs/aio.c')
-rw-r--r--fs/aio.c19
1 files 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;
@@ -707,6 +706,12 @@ static struct kioctx *ioctx_alloc(unsigned nr_events)
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;