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-rw-r--r--fs/cifs/cifssmb.c30
1 files changed, 30 insertions, 0 deletions
diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c
index 6b79efd7d75f..3a75ee5a6b33 100644
--- a/fs/cifs/cifssmb.c
+++ b/fs/cifs/cifssmb.c
@@ -89,6 +89,32 @@ static struct {
/* Forward declarations */
static void cifs_readv_complete(struct work_struct *work);
+#ifdef CONFIG_HIGHMEM
+/*
+ * On arches that have high memory, kmap address space is limited. By
+ * serializing the kmap operations on those arches, we ensure that we don't
+ * end up with a bunch of threads in writeback with partially mapped page
+ * arrays, stuck waiting for kmap to come back. That situation prevents
+ * progress and can deadlock.
+ */
+static DEFINE_MUTEX(cifs_kmap_mutex);
+
+static inline void
+cifs_kmap_lock(void)
+{
+ mutex_lock(&cifs_kmap_mutex);
+}
+
+static inline void
+cifs_kmap_unlock(void)
+{
+ mutex_unlock(&cifs_kmap_mutex);
+}
+#else /* !CONFIG_HIGHMEM */
+#define cifs_kmap_lock() do { ; } while(0)
+#define cifs_kmap_unlock() do { ; } while(0)
+#endif /* CONFIG_HIGHMEM */
+
/* Mark as invalid, all open files on tree connections since they
were closed when session to server was lost */
static void mark_open_files_invalid(struct cifs_tcon *pTcon)
@@ -1557,6 +1583,7 @@ cifs_readv_receive(struct TCP_Server_Info *server, struct mid_q_entry *mid)
eof_index = eof ? (eof - 1) >> PAGE_CACHE_SHIFT : 0;
cFYI(1, "eof=%llu eof_index=%lu", eof, eof_index);
+ cifs_kmap_lock();
list_for_each_entry_safe(page, tpage, &rdata->pages, lru) {
if (remaining >= PAGE_CACHE_SIZE) {
/* enough data to fill the page */
@@ -1606,6 +1633,7 @@ cifs_readv_receive(struct TCP_Server_Info *server, struct mid_q_entry *mid)
page_cache_release(page);
}
}
+ cifs_kmap_unlock();
/* issue the read if we have any iovecs left to fill */
if (rdata->nr_iov > 1) {
@@ -2194,7 +2222,9 @@ cifs_async_writev(struct cifs_writedata *wdata)
* and set the iov_len properly for each one. It may also set
* wdata->bytes too.
*/
+ cifs_kmap_lock();
wdata->marshal_iov(iov, wdata);
+ cifs_kmap_unlock();
cFYI(1, "async write at %llu %u bytes", wdata->offset, wdata->bytes);