* Davidlohr Bueso <d...@stgolabs.net> [2014-10-24 15:06:15]:
> Both register and unregister call build_map_info() in order
> to create the list of mappings before installing or removing
> breakpoints for every mm which maps file backed memory. As
> such, there is no reason to hold the i_mmap_rwsem exclusively,
> so share it and allow concurrent readers to build the mapping
> data.
>
> Signed-off-by: Davidlohr Bueso <dbu...@suse.de>
Copying Oleg (since he should have been copied on this one)
Please see one comment below.
Acked-by: Srikar Dronamraju <sri...@linux.vnet.ibm.com>
> ---
> kernel/events/uprobes.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> index 045b649..7a9e620 100644
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -724,7 +724,7 @@ build_map_info(struct address_space *mapping, loff_t
> offset, bool is_register)
> int more = 0;
>
> again:
> - i_mmap_lock_write(mapping);
> + i_mmap_lock_read(mapping);
> vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
> if (!valid_vma(vma, is_register))
> continue;
Just after this, we have
if (!prev && !more) {
/*
* Needs GFP_NOWAIT to avoid i_mmap_mutex recursion through
* reclaim. This is optimistic, no harm done if it fails.
*/
prev = kmalloc(sizeof(struct map_info),
GFP_NOWAIT | __GFP_NOMEMALLOC | __GFP_NOWARN);
if (prev)
prev->next = NULL;
}
However in patch 02/10
I dont think the comment referring to i_mmap_mutex was modified to
refer i_mmap_lock_write.
When thats taken care off, this patch should change that part accordingly.
--
Thanks and Regards
Srikar Dronamraju
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