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Date: Sat, 1 Sep 2007 22:46:53 -0400
From: Matthew Wilcox <matthew@....cx>
To: akpm@...l.org, torvalds@...l.org
Cc: linux-kernel@...r.kernel.org, Matthew Wilcox <matthew@....cx>
Subject: [PATCH 4/5] Add lock_page_killable
and associated infrastructure such as sync_page_killable and
fatal_signal_pending. Use lock_page_killable in do_generic_mapping_read()
to allow us to kill `cat' of a file on an NFS-mounted filesystem.
Signed-off-by: Matthew Wilcox <matthew@....cx>
---
include/linux/pagemap.h | 14 ++++++++++++++
include/linux/sched.h | 9 ++++++++-
kernel/signal.c | 5 +++++
mm/filemap.c | 25 +++++++++++++++++++++----
4 files changed, 48 insertions(+), 5 deletions(-)
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 8a83537..8b4f533 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -154,6 +154,7 @@ static inline pgoff_t linear_page_index(struct vm_area_struct *vma,
}
extern void FASTCALL(__lock_page(struct page *page));
+extern int FASTCALL(__lock_page_killable(struct page *page));
extern void FASTCALL(__lock_page_nosync(struct page *page));
extern void FASTCALL(unlock_page(struct page *page));
@@ -168,6 +169,19 @@ static inline void lock_page(struct page *page)
}
/*
+ * lock_page_killable is like lock_page but can be interrupted by fatal
+ * signals. It returns 0 if it locked the page and -EINTR if it was
+ * killed while waiting.
+ */
+static inline int lock_page_killable(struct page *page)
+{
+ might_sleep();
+ if (TestSetPageLocked(page))
+ return __lock_page_killable(page);
+ return 0;
+}
+
+/*
* lock_page_nosync should only be used if we can't pin the page's inode.
* Doesn't play quite so well with block device plugging.
*/
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 6769179..e6f20da 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1769,7 +1769,14 @@ static inline int signal_pending(struct task_struct *p)
{
return unlikely(test_tsk_thread_flag(p,TIF_SIGPENDING));
}
-
+
+extern int FASTCALL(__fatal_signal_pending(struct task_struct *p));
+
+static inline int fatal_signal_pending(struct task_struct *p)
+{
+ return signal_pending(p) && __fatal_signal_pending(p);
+}
+
static inline int need_resched(void)
{
return unlikely(test_thread_flag(TIF_NEED_RESCHED));
diff --git a/kernel/signal.c b/kernel/signal.c
index 986ba10..2b4fe29 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1003,6 +1003,11 @@ void zap_other_threads(struct task_struct *p)
}
}
+int fastcall __fatal_signal_pending(struct task_struct *tsk)
+{
+ return sigismember(&tsk->pending.signal, SIGKILL);
+}
+
/*
* Must be called under rcu_read_lock() or with tasklist_lock read-held.
*/
diff --git a/mm/filemap.c b/mm/filemap.c
index 90b657b..235f092 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -170,6 +170,12 @@ static int sync_page(void *word)
return 0;
}
+static int sync_page_killable(void *word)
+{
+ sync_page(word);
+ return fatal_signal_pending(current) ? -EINTR : 0;
+}
+
/**
* __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
* @mapping: address space structure to write
@@ -574,6 +580,14 @@ void fastcall __lock_page(struct page *page)
}
EXPORT_SYMBOL(__lock_page);
+int fastcall __lock_page_killable(struct page *page)
+{
+ DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
+
+ return __wait_on_bit_lock(page_waitqueue(page), &wait,
+ sync_page_killable, TASK_KILLABLE);
+}
+
/*
* Variant of lock_page that does not require the caller to hold a reference
* on the page's mapping.
@@ -975,7 +989,8 @@ page_ok:
page_not_up_to_date:
/* Get exclusive access to the page ... */
- lock_page(page);
+ if (lock_page_killable(page))
+ goto readpage_eio;
/* Did it get truncated before we got the lock? */
if (!page->mapping) {
@@ -1003,7 +1018,8 @@ readpage:
}
if (!PageUptodate(page)) {
- lock_page(page);
+ if (lock_page_killable(page))
+ goto readpage_eio;
if (!PageUptodate(page)) {
if (page->mapping == NULL) {
/*
@@ -1014,15 +1030,16 @@ readpage:
goto find_page;
}
unlock_page(page);
- error = -EIO;
shrink_readahead_size_eio(filp, &ra);
- goto readpage_error;
+ goto readpage_eio;
}
unlock_page(page);
}
goto page_ok;
+readpage_eio:
+ error = -EIO;
readpage_error:
/* UHHUH! A synchronous read error occurred. Report it */
desc->error = error;
--
1.4.4.2
-
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