fs: new infrastructure for writeback error handling and reporting

[mirror_ubuntu-artful-kernel.git] / include / linux / fs.h

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 8ac8df1b3550196be5067f62293cbca3cbde3e67..78b5c2901712ff07abbd549ca7c18d2183ac418e 100644 (file)
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -30,7 +30,7 @@
 #include <linux/percpu-rwsem.h>
 #include <linux/workqueue.h>
 #include <linux/delayed_call.h>
-
+#include <linux/errseq.h>
 #include <asm/byteorder.h>
 #include <uapi/linux/fs.h>
 
@@ -392,6 +392,7 @@ struct address_space {
        gfp_t                   gfp_mask;       /* implicit gfp mask for allocations */
        struct list_head        private_list;   /* ditto */
        void                    *private_data;  /* ditto */
+       errseq_t                wb_err;
 } __attribute__((aligned(sizeof(long))));
        /*
         * On most architectures that alignment is already the case; but
@@ -868,6 +869,7 @@ struct file {
        struct list_head        f_tfile_llink;
 #endif /* #ifdef CONFIG_EPOLL */
        struct address_space    *f_mapping;
+       errseq_t                f_wb_err;
 } __attribute__((aligned(4))); /* lest something weird decides that 2 is OK */
 
 struct file_handle {
@@ -2526,6 +2528,62 @@ extern int filemap_fdatawrite_range(struct address_space *mapping,
                                loff_t start, loff_t end);
 extern int filemap_check_errors(struct address_space *mapping);
 
+extern void __filemap_set_wb_err(struct address_space *mapping, int err);
+extern int __must_check file_check_and_advance_wb_err(struct file *file);
+extern int __must_check file_write_and_wait_range(struct file *file,
+                                               loff_t start, loff_t end);
+
+/**
+ * filemap_set_wb_err - set a writeback error on an address_space
+ * @mapping: mapping in which to set writeback error
+ * @err: error to be set in mapping
+ *
+ * When writeback fails in some way, we must record that error so that
+ * userspace can be informed when fsync and the like are called.  We endeavor
+ * to report errors on any file that was open at the time of the error.  Some
+ * internal callers also need to know when writeback errors have occurred.
+ *
+ * When a writeback error occurs, most filesystems will want to call
+ * filemap_set_wb_err to record the error in the mapping so that it will be
+ * automatically reported whenever fsync is called on the file.
+ *
+ * FIXME: mention FS_* flag here?
+ */
+static inline void filemap_set_wb_err(struct address_space *mapping, int err)
+{
+       /* Fastpath for common case of no error */
+       if (unlikely(err))
+               __filemap_set_wb_err(mapping, err);
+}
+
+/**
+ * filemap_check_wb_error - has an error occurred since the mark was sampled?
+ * @mapping: mapping to check for writeback errors
+ * @since: previously-sampled errseq_t
+ *
+ * Grab the errseq_t value from the mapping, and see if it has changed "since"
+ * the given value was sampled.
+ *
+ * If it has then report the latest error set, otherwise return 0.
+ */
+static inline int filemap_check_wb_err(struct address_space *mapping,
+                                       errseq_t since)
+{
+       return errseq_check(&mapping->wb_err, since);
+}
+
+/**
+ * filemap_sample_wb_err - sample the current errseq_t to test for later errors
+ * @mapping: mapping to be sampled
+ *
+ * Writeback errors are always reported relative to a particular sample point
+ * in the past. This function provides those sample points.
+ */
+static inline errseq_t filemap_sample_wb_err(struct address_space *mapping)
+{
+       return errseq_sample(&mapping->wb_err);
+}
+
 extern int vfs_fsync_range(struct file *file, loff_t start, loff_t end,
                           int datasync);
 extern int vfs_fsync(struct file *file, int datasync);