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Subject[PATCH 02/10] Introduce mm_has_pending_aio() helper
Date
From: Nathan Lynch <ntl@pobox.com>

Support for AIO is on the to-do list, but until that is implemented,
checkpoint will have to fail if a mm_struct has outstanding AIO
contexts. Add a mm_has_pending_aio() helper function for this
purpose.

Based on original "check_for_outstanding_aio" patch by Serge Hallyn.

Signed-off-by: Serge E. Hallyn <serge@hallyn.com>
[ntl: changed name and return type to clearly express semantics]
[ntl: added kerneldoc]
Signed-off-by: Nathan Lynch <ntl@pobox.com>
---
fs/aio.c | 27 +++++++++++++++++++++++++++
include/linux/aio.h | 2 ++
2 files changed, 29 insertions(+), 0 deletions(-)

diff --git a/fs/aio.c b/fs/aio.c
index 8c8f6c5..1acbc99 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -1847,3 +1847,30 @@ SYSCALL_DEFINE5(io_getevents, aio_context_t, ctx_id,
asmlinkage_protect(5, ret, ctx_id, min_nr, nr, events, timeout);
return ret;
}
+
+/**
+ * mm_has_pending_aio() - check for outstanding AIO operations
+ * @mm: The mm_struct to check.
+ *
+ * Returns true if there is at least one non-dead kioctx on
+ * @mm->ioctx_list. Note that the result of this function is
+ * unreliable unless the caller has ensured that new requests cannot
+ * be submitted against @mm (e.g. through freezing the associated
+ * tasks).
+ */
+bool mm_has_pending_aio(struct mm_struct *mm)
+{
+ struct kioctx *ctx;
+ struct hlist_node *n;
+ bool has_aio = false;
+
+ rcu_read_lock();
+ hlist_for_each_entry_rcu(ctx, n, &mm->ioctx_list, list) {
+ if (!ctx->dead) {
+ has_aio = true;
+ break;
+ }
+ }
+ rcu_read_unlock();
+ return has_aio;
+}
diff --git a/include/linux/aio.h b/include/linux/aio.h
index 7a8db41..39d9936 100644
--- a/include/linux/aio.h
+++ b/include/linux/aio.h
@@ -214,6 +214,7 @@ struct mm_struct;
extern void exit_aio(struct mm_struct *mm);
extern long do_io_submit(aio_context_t ctx_id, long nr,
struct iocb __user *__user *iocbpp, bool compat);
+extern bool mm_has_pending_aio(struct mm_struct *mm);
#else
static inline ssize_t wait_on_sync_kiocb(struct kiocb *iocb) { return 0; }
static inline int aio_put_req(struct kiocb *iocb) { return 0; }
@@ -224,6 +225,7 @@ static inline void exit_aio(struct mm_struct *mm) { }
static inline long do_io_submit(aio_context_t ctx_id, long nr,
struct iocb __user * __user *iocbpp,
bool compat) { return 0; }
+static inline bool mm_has_pending_aio(struct mm_struct *mm) { return false; }
#endif /* CONFIG_AIO */

static inline struct kiocb *list_kiocb(struct list_head *h)
--
1.7.4


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