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NFS: Ensure we always dereference the page head last

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This fixes a race with nfs_page_group_sync_on_bit() whereby the
call to wake_up_bit() in nfs_page_group_unlock() could occur after
the page header had been freed.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
This commit is contained in:
Trond Myklebust 2017-07-18 19:31:10 -04:00
parent 1403390d83
commit 08fead2ae5
1 changed files with 6 additions and 5 deletions
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11
fs/nfs/pagelist.c
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@ -306,14 +306,11 @@ static void
nfs_page_group_destroy(struct kref *kref)
{
struct nfs_page *req = container_of(kref, struct nfs_page, wb_kref);
struct nfs_page *head = req->wb_head;
struct nfs_page *tmp, *next;
/* subrequests must release the ref on the head request */
if (req->wb_head != req)
nfs_release_request(req->wb_head);
if (!nfs_page_group_sync_on_bit(req, PG_TEARDOWN))
return;
goto out;
tmp = req;
do {
@ -324,6 +321,10 @@ nfs_page_group_destroy(struct kref *kref)
nfs_free_request(tmp);
tmp = next;
} while (tmp != req);
out:
/* subrequests must release the ref on the head request */
if (head != req)
nfs_release_request(head);
}
/**