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| author | Ross Lagerwall <ross.lagerwall@citrix.com> | 2018-01-11 09:36:37 +0000 |
|---|---|---|
| committer | Juergen Gross <jgross@suse.com> | 2018-02-06 09:55:37 +0100 |
| commit | 3ac7292a25db1c607a50752055a18aba32ac2176 (patch) | |
| tree | fc61e3f29d937cff55bb19eb953cb64f8190e018 /drivers/xen/grant-table.c | |
| parent | 4f277295e54c5b7340e48efea3fc5cc21a2872b7 (diff) | |
| download | lwn-3ac7292a25db1c607a50752055a18aba32ac2176.tar.gz lwn-3ac7292a25db1c607a50752055a18aba32ac2176.zip | |
xen/grant-table: Use put_page instead of free_page
The page given to gnttab_end_foreign_access() to free could be a
compound page so use put_page() instead of free_page() since it can
handle both compound and single pages correctly.
This bug was discovered when migrating a Xen VM with several VIFs and
CONFIG_DEBUG_VM enabled. It hits a BUG usually after fewer than 10
iterations. All netfront devices disconnect from the backend during a
suspend/resume and this will call gnttab_end_foreign_access() if a
netfront queue has an outstanding skb. The mismatch between calling
get_page() and free_page() on a compound page causes a reference
counting error which is detected when DEBUG_VM is enabled.
Signed-off-by: Ross Lagerwall <ross.lagerwall@citrix.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Diffstat (limited to 'drivers/xen/grant-table.c')
| -rw-r--r-- | drivers/xen/grant-table.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c index f45114fd8e1e..27be107d6480 100644 --- a/drivers/xen/grant-table.c +++ b/drivers/xen/grant-table.c @@ -382,7 +382,7 @@ static void gnttab_handle_deferred(struct timer_list *unused) if (entry->page) { pr_debug("freeing g.e. %#x (pfn %#lx)\n", entry->ref, page_to_pfn(entry->page)); - __free_page(entry->page); + put_page(entry->page); } else pr_info("freeing g.e. %#x\n", entry->ref); kfree(entry); @@ -438,7 +438,7 @@ void gnttab_end_foreign_access(grant_ref_t ref, int readonly, if (gnttab_end_foreign_access_ref(ref, readonly)) { put_free_entry(ref); if (page != 0) - free_page(page); + put_page(virt_to_page(page)); } else gnttab_add_deferred(ref, readonly, page ? virt_to_page(page) : NULL); |