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mm/vmalloc: prevent flushing dirty space over and over 

vmap blocks which have active mappings cannot be purged.  Allocations
which have been freed are accounted for in vmap_block::dirty_min/max, so
that they can be detected in _vm_unmap_aliases() as potentially stale
TLBs.

If there are several invocations of _vm_unmap_aliases() then each of them
will flush the dirty range.  That's pointless and just increases the
probability of full TLB flushes.

Avoid that by resetting the flush range after accounting for it.  That's
safe versus other invocations of _vm_unmap_aliases() because this is all
serialized with vmap_purge_lock.

Link: https://lkml.kernel.org/r/20230525124504.692056496@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Baoquan He <bhe@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Thomas Gleixner 2023-05-25 14:57:05 +02:00 committed by Andrew Morton
parent ca5e46c340
commit a09fad96ff
1 changed files with 6 additions and 2 deletions
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8
mm/vmalloc.c
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@ -2226,7 +2226,7 @@ static void vb_free(unsigned long addr, unsigned long size)
spin_lock(&vb->lock);
/* Expand dirty range */
/* Expand the not yet TLB flushed dirty range */
vb->dirty_min = min(vb->dirty_min, offset);
vb->dirty_max = max(vb->dirty_max, offset + (1UL << order));
@ -2264,7 +2264,7 @@ static void _vm_unmap_aliases(unsigned long start, unsigned long end, int flush)
* space to be flushed.
*/
if (!purge_fragmented_block(vb, vbq, &purge_list) &&
vb->dirty && vb->dirty != VMAP_BBMAP_BITS) {
vb->dirty_max && vb->dirty != VMAP_BBMAP_BITS) {
unsigned long va_start = vb->va->va_start;
unsigned long s, e;
@ -2274,6 +2274,10 @@ static void _vm_unmap_aliases(unsigned long start, unsigned long end, int flush)
start = min(s, start);
end = max(e, end);
/* Prevent that this is flushed again */
vb->dirty_min = VMAP_BBMAP_BITS;
vb->dirty_max = 0;
flush = 1;
}
spin_unlock(&vb->lock);