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NFS: Fix a potential busy wait in nfs_page_group_lock

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We cannot allow nfs_page_group_lock to use TASK_KILLABLE here, since
the loop would cause a busy wait if somebody kills the task.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
This commit is contained in:
Trond Myklebust 2014-05-29 11:45:57 -04:00
parent c1109558ae
commit f868089b09
1 changed files with 9 additions and 10 deletions
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19
fs/nfs/pagelist.c
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@ -138,6 +138,12 @@ nfs_iocounter_wait(struct nfs_io_counter *c)
return __nfs_iocounter_wait(c);
}
static int nfs_wait_bit_uninterruptible(void *word)
{
io_schedule();
return 0;
}
/*
* nfs_page_group_lock - lock the head of the page group
* @req - request in group that is to be locked
@ -148,13 +154,12 @@ void
nfs_page_group_lock(struct nfs_page *req)
{
struct nfs_page *head = req->wb_head;
int err = -EAGAIN;
WARN_ON_ONCE(head != head->wb_head);
while (err)
err = wait_on_bit_lock(&head->wb_flags, PG_HEADLOCK,
nfs_wait_bit_killable, TASK_KILLABLE);
wait_on_bit_lock(&head->wb_flags, PG_HEADLOCK,
nfs_wait_bit_uninterruptible,
TASK_UNINTERRUPTIBLE);
}
/*
@ -410,12 +415,6 @@ void nfs_release_request(struct nfs_page *req)
kref_put(&req->wb_kref, nfs_page_group_destroy);
}
static int nfs_wait_bit_uninterruptible(void *word)
{
io_schedule();
return 0;
}
/**
* nfs_wait_on_request - Wait for a request to complete.
* @req: request to wait upon.