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authorPeter Xu <peterx@redhat.com>2022-08-11 12:13:30 -0400
committerAndrew Morton <akpm@linux-foundation.org>2022-09-26 19:46:05 -0700
commitbe45a4902c7caa717fee6b2f671e59b396ed395c (patch)
treea2fc0b0484f3e38a01547afab2e2f0aabcdaa231 /mm/swapfile.c
parent2e3468778dbe3ec389a10c21a703bb8e5be5cfbc (diff)
mm/swap: cache maximum swapfile size when init swap
We used to have swapfile_maximum_size() fetching a maximum value of swapfile size per-arch. As the caller of max_swapfile_size() grows, this patch introduce a variable "swapfile_maximum_size" and cache the value of old max_swapfile_size(), so that we don't need to calculate the value every time. Caching the value in swapfile_init() is safe because when reaching the phase we should have initialized all the relevant information. Here the major arch to take care of is x86, which defines the max swapfile size based on L1TF mitigation. Here both X86_BUG_L1TF or l1tf_mitigation should have been setup properly when reaching swapfile_init(). As a reference, the code path looks like this for x86: - start_kernel - setup_arch - early_cpu_init - early_identify_cpu --> setup X86_BUG_L1TF - parse_early_param - l1tf_cmdline --> set l1tf_mitigation - check_bugs - l1tf_select_mitigation --> set l1tf_mitigation - arch_call_rest_init - rest_init - kernel_init - kernel_init_freeable - do_basic_setup - do_initcalls --> calls swapfile_init() (initcall level 4) The swapfile size only depends on swp pte format on non-x86 archs, so caching it is safe too. Since at it, rename max_swapfile_size() to arch_max_swapfile_size() because arch can define its own function, so it's more straightforward to have "arch_" as its prefix. At the meantime, export swapfile_maximum_size to replace the old usages of max_swapfile_size(). [peterx@redhat.com: declare arch_max_swapfile_size) in swapfile.h] Link: https://lkml.kernel.org/r/YxTh1GuC6ro5fKL5@xz-m1.local Link: https://lkml.kernel.org/r/20220811161331.37055-7-peterx@redhat.com Signed-off-by: Peter Xu <peterx@redhat.com> Reviewed-by: "Huang, Ying" <ying.huang@intel.com> Cc: Alistair Popple <apopple@nvidia.com> Cc: Andi Kleen <andi.kleen@intel.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: David Hildenbrand <david@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: "Kirill A . Shutemov" <kirill@shutemov.name> Cc: Minchan Kim <minchan@kernel.org> Cc: Nadav Amit <nadav.amit@gmail.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Dave Hansen <dave.hansen@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm/swapfile.c')
-rw-r--r--mm/swapfile.c7
1 files changed, 5 insertions, 2 deletions
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 1fdccd2f1422..3cc64399df44 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -63,6 +63,7 @@ EXPORT_SYMBOL_GPL(nr_swap_pages);
/* protected with swap_lock. reading in vm_swap_full() doesn't need lock */
long total_swap_pages;
static int least_priority = -1;
+unsigned long swapfile_maximum_size;
static const char Bad_file[] = "Bad swap file entry ";
static const char Unused_file[] = "Unused swap file entry ";
@@ -2816,7 +2817,7 @@ unsigned long generic_max_swapfile_size(void)
}
/* Can be overridden by an architecture for additional checks. */
-__weak unsigned long max_swapfile_size(void)
+__weak unsigned long arch_max_swapfile_size(void)
{
return generic_max_swapfile_size();
}
@@ -2856,7 +2857,7 @@ static unsigned long read_swap_header(struct swap_info_struct *p,
p->cluster_next = 1;
p->cluster_nr = 0;
- maxpages = max_swapfile_size();
+ maxpages = swapfile_maximum_size;
last_page = swap_header->info.last_page;
if (!last_page) {
pr_warn("Empty swap-file\n");
@@ -3677,6 +3678,8 @@ static int __init swapfile_init(void)
for_each_node(nid)
plist_head_init(&swap_avail_heads[nid]);
+ swapfile_maximum_size = arch_max_swapfile_size();
+
return 0;
}
subsys_initcall(swapfile_init);