exofs: Define on-disk per-inode optional layout attribute

* Layouts describe the way a file is spread on multiple devices.
  The layout information is stored in the objects attribute introduced
  in this patch.

* There can be multiple generating function for the layout.
  Currently defined:
    - No attribute present - use below moving-window on global
      device table, all devices.
      (This is the only one currently used in exofs)
    - an obj_id generated moving window - the obj_id is a randomizing
      factor in the otherwise global map layout.
    - An explicit layout stored, including a data_map and a device
      index list.
    - More might be defined in future ...

* There are two attributes defined of the same structure:
  A-data-files-layout - This layout is used by data-files. If present
                        at a directory, all files of that directory will
                        be created with this layout.
  A-meta-data-layout - This layout is used by a directory and other
                       meta-data information. Also inherited at creation
                       of subdirectories.

* At creation time inodes are created with the layout specified above.
  A usermode utility may change the creation layout on a give directory
  or file. Which in the case of directories, will also apply to newly
  created files/subdirectories, children of that directory.
  In the simple unaltered case of a newly created exofs, no layout
  attributes are present, and all layouts adhere to the layout specified
  at the device-table.

* In case of a future file system loaded in an old exofs-driver.
  At iget(), the generating_function is inspected and if not supported
  will return an IO error to the application and the inode will not
  be loaded. So not to damage any data.
  Note: After this patch we do not yet support any type of layout
        only the RAID0 patch that enables striping at the super-block
        level will add support for RAID0 layouts above. This way we
        are past and future compatible and fully bisectable.

* Access to the device table is done by an accessor since
  it will change according to above information.

Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>

4 files changed, 114 insertions, 10 deletions

diff --git a/fs/exofs/common.h b/fs/exofs/common.h
index b1b178e61718..f0d520312d8b 100644
--- a/fs/exofs/common.h
+++ b/fs/exofs/common.h
@@ -55,6 +55,8 @@
 /* exofs Application specific page/attribute */
 # define EXOFS_APAGE_FS_DATA    (OSD_APAGE_APP_DEFINED_FIRST + 3)
 # define EXOFS_ATTR_INODE_DATA  1
+# define EXOFS_ATTR_INODE_FILE_LAYOUT   2
+# define EXOFS_ATTR_INODE_DIR_LAYOUT    3
 
 /*
  * The maximum number of files we can have is limited by the size of the
@@ -206,4 +208,41 @@ enum {
         (((name_len) + offsetof(struct exofs_dir_entry, name)  + \
           EXOFS_DIR_ROUND) & ~EXOFS_DIR_ROUND)
 
+/*
+ * The on-disk (optional) layout structure.
+ * sits in an EXOFS_ATTR_INODE_FILE_LAYOUT or EXOFS_ATTR_INODE_DIR_LAYOUT
+ * attribute, attached to any inode, usually to a directory.
+ */
+
+enum exofs_inode_layout_gen_functions {
+        LAYOUT_MOVING_WINDOW = 0,
+        LAYOUT_IMPLICT = 1,
+};
+
+struct exofs_on_disk_inode_layout {
+        __le16 gen_func; /* One of enum exofs_inode_layout_gen_functions */
+        __le16 pad;
+        union {
+                /* gen_func == LAYOUT_MOVING_WINDOW (default) */
+                struct exofs_layout_sliding_window {
+                        __le32 num_devices; /* first n devices in global-table*/
+                } sliding_window __packed;
+
+                /* gen_func == LAYOUT_IMPLICT */
+                struct exofs_layout_implict_list {
+                        struct exofs_dt_data_map data_map;
+                        /* Variable array of size data_map.cb_num_comps. These
+                         * are device indexes of the devices in the global table
+                         */
+                        __le32 dev_indexes[];
+                } implict __packed;
+        };
+} __packed;
+
+static inline size_t exofs_on_disk_inode_layout_size(unsigned max_devs)
+{
+        return sizeof(struct exofs_on_disk_inode_layout) +
+                max_devs * sizeof(__le32);
+}
+
 #endif /*ifndef __EXOFS_COM_H__*/
diff --git a/fs/exofs/exofs.h b/fs/exofs/exofs.h
index 33c68568b338..09e331935514 100644
--- a/fs/exofs/exofs.h
+++ b/fs/exofs/exofs.h
@@ -186,6 +186,12 @@ static inline struct exofs_i_info *exofs_i(struct inode *inode)
 }
 
 /*
+ * Given a layout, object_number and stripe_index return the associated global
+ * dev_index
+ */
+unsigned exofs_layout_od_id(struct exofs_layout *layout,
+                            osd_id obj_no, unsigned layout_index);
+/*
  * Maximum count of links to a file
  */
 #define EXOFS_LINK_MAX           32000
diff --git a/fs/exofs/inode.c b/fs/exofs/inode.c
index 03189a958b33..0163546ba05a 100644
--- a/fs/exofs/inode.c
+++ b/fs/exofs/inode.c
@@ -859,6 +859,15 @@ int exofs_setattr(struct dentry *dentry, struct iattr *iattr)
         return error;
 }
 
+static const struct osd_attr g_attr_inode_file_layout = ATTR_DEF(
+        EXOFS_APAGE_FS_DATA,
+        EXOFS_ATTR_INODE_FILE_LAYOUT,
+        0);
+static const struct osd_attr g_attr_inode_dir_layout = ATTR_DEF(
+        EXOFS_APAGE_FS_DATA,
+        EXOFS_ATTR_INODE_DIR_LAYOUT,
+        0);
+
 /*
  * Read an inode from the OSD, and return it as is.  We also return the size
  * attribute in the 'obj_size' argument.
@@ -867,11 +876,16 @@ static int exofs_get_inode(struct super_block *sb, struct exofs_i_info *oi,
                     struct exofs_fcb *inode, uint64_t *obj_size)
 {
         struct exofs_sb_info *sbi = sb->s_fs_info;
-        struct osd_attr attrs[2];
+        struct osd_attr attrs[] = {
+                [0] = g_attr_inode_data,
+                [1] = g_attr_inode_file_layout,
+                [2] = g_attr_inode_dir_layout,
+                [3] = g_attr_logical_length,
+        };
         struct exofs_io_state *ios;
+        struct exofs_on_disk_inode_layout *layout;
         int ret;
 
-        *obj_size = ~0;
         ret = exofs_get_io_state(&sbi->layout, &ios);
         if (unlikely(ret)) {
                 EXOFS_ERR("%s: exofs_get_io_state failed.\n", __func__);
@@ -882,8 +896,9 @@ static int exofs_get_inode(struct super_block *sb, struct exofs_i_info *oi,
         exofs_make_credential(oi->i_cred, &ios->obj);
         ios->cred = oi->i_cred;
 
-        attrs[0] = g_attr_inode_data;
-        attrs[1] = g_attr_logical_length;
+        attrs[1].len = exofs_on_disk_inode_layout_size(sbi->layout.s_numdevs);
+        attrs[2].len = exofs_on_disk_inode_layout_size(sbi->layout.s_numdevs);
+
         ios->in_attr = attrs;
         ios->in_attr_len = ARRAY_SIZE(attrs);
 
@@ -901,11 +916,42 @@ static int exofs_get_inode(struct super_block *sb, struct exofs_i_info *oi,
 
         ret = extract_attr_from_ios(ios, &attrs[1]);
         if (ret) {
+                EXOFS_ERR("%s: extract_attr of inode_data failed\n", __func__);
+                goto out;
+        }
+        if (attrs[1].len) {
+                layout = attrs[1].val_ptr;
+                if (layout->gen_func != cpu_to_le16(LAYOUT_MOVING_WINDOW)) {
+                        EXOFS_ERR("%s: unsupported files layout %d\n",
+                                __func__, layout->gen_func);
+                        ret = -ENOTSUPP;
+                        goto out;
+                }
+        }
+
+        ret = extract_attr_from_ios(ios, &attrs[2]);
+        if (ret) {
+                EXOFS_ERR("%s: extract_attr of inode_data failed\n", __func__);
+                goto out;
+        }
+        if (attrs[2].len) {
+                layout = attrs[2].val_ptr;
+                if (layout->gen_func != cpu_to_le16(LAYOUT_MOVING_WINDOW)) {
+                        EXOFS_ERR("%s: unsupported meta-data layout %d\n",
+                                __func__, layout->gen_func);
+                        ret = -ENOTSUPP;
+                        goto out;
+                }
+        }
+
+        *obj_size = ~0;
+        ret = extract_attr_from_ios(ios, &attrs[3]);
+        if (ret) {
                 EXOFS_ERR("%s: extract_attr of logical_length failed\n",
                           __func__);
                 goto out;
         }
-        *obj_size = get_unaligned_be64(attrs[1].val_ptr);
+        *obj_size = get_unaligned_be64(attrs[3].val_ptr);
 
 out:
         exofs_put_io_state(ios);
diff --git a/fs/exofs/ios.c b/fs/exofs/ios.c
index 4f679317ca54..2b81f99fd62c 100644
--- a/fs/exofs/ios.c
+++ b/fs/exofs/ios.c
@@ -107,6 +107,19 @@ void exofs_put_io_state(struct exofs_io_state *ios)
         }
 }
 
+unsigned exofs_layout_od_id(struct exofs_layout *layout,
+                            osd_id obj_no, unsigned layout_index)
+{
+        return layout_index;
+}
+
+static inline struct osd_dev *exofs_ios_od(struct exofs_io_state *ios,
+                                           unsigned layout_index)
+{
+        return ios->layout->s_ods[
+                exofs_layout_od_id(ios->layout, ios->obj.id, layout_index)];
+}
+
 static void _sync_done(struct exofs_io_state *ios, void *p)
 {
         struct completion *waiting = p;
@@ -242,7 +255,7 @@ int exofs_sbi_create(struct exofs_io_state *ios)
         for (i = 0; i < ios->layout->s_numdevs; i++) {
                 struct osd_request *or;
 
-                or = osd_start_request(ios->layout->s_ods[i], GFP_KERNEL);
+                or = osd_start_request(exofs_ios_od(ios, i), GFP_KERNEL);
                 if (unlikely(!or)) {
                         EXOFS_ERR("%s: osd_start_request failed\n", __func__);
                         ret = -ENOMEM;
@@ -266,7 +279,7 @@ int exofs_sbi_remove(struct exofs_io_state *ios)
         for (i = 0; i < ios->layout->s_numdevs; i++) {
                 struct osd_request *or;
 
-                or = osd_start_request(ios->layout->s_ods[i], GFP_KERNEL);
+                or = osd_start_request(exofs_ios_od(ios, i), GFP_KERNEL);
                 if (unlikely(!or)) {
                         EXOFS_ERR("%s: osd_start_request failed\n", __func__);
                         ret = -ENOMEM;
@@ -290,7 +303,7 @@ int exofs_sbi_write(struct exofs_io_state *ios)
         for (i = 0; i < ios->layout->s_numdevs; i++) {
                 struct osd_request *or;
 
-                or = osd_start_request(ios->layout->s_ods[i], GFP_KERNEL);
+                or = osd_start_request(exofs_ios_od(ios, i), GFP_KERNEL);
                 if (unlikely(!or)) {
                         EXOFS_ERR("%s: osd_start_request failed\n", __func__);
                         ret = -ENOMEM;
@@ -361,7 +374,7 @@ int exofs_sbi_read(struct exofs_io_state *ios)
         unsigned first_dev = (unsigned)ios->obj.id;
 
         first_dev %= ios->layout->s_numdevs;
-        or = osd_start_request(ios->layout->s_ods[first_dev], GFP_KERNEL);
+        or = osd_start_request(exofs_ios_od(ios, first_dev), GFP_KERNEL);
         if (unlikely(!or)) {
                 EXOFS_ERR("%s: osd_start_request failed\n", __func__);
                 return -ENOMEM;
@@ -442,7 +455,7 @@ int exofs_oi_truncate(struct exofs_i_info *oi, u64 size)
         for (i = 0; i < sbi->layout.s_numdevs; i++) {
                 struct osd_request *or;
 
-                or = osd_start_request(sbi->layout.s_ods[i], GFP_KERNEL);
+                or = osd_start_request(exofs_ios_od(ios, i), GFP_KERNEL);
                 if (unlikely(!or)) {
                         EXOFS_ERR("%s: osd_start_request failed\n", __func__);
                         ret = -ENOMEM;