[Qemu-devel] [PATCH v2 1/7] md: add support for simultaneous disk failure on the same node

[Liu Yuan]

From: Liu Yuan <address@hidden>

Don't panic out, instead we simply remove this disk for this nested disk
failures.

Signed-off-by: Liu Yuan <address@hidden>
---
 sheep/md.c |   66 +++++++++++++++++++++++++++++++++++++++++++-----------------
 1 file changed, 48 insertions(+), 18 deletions(-)

diff --git a/sheep/md.c b/sheep/md.c
index ed474c8..821a391 100644
--- a/sheep/md.c
+++ b/sheep/md.c
@@ -154,40 +154,77 @@ static inline void calculate_vdisks(struct disk *disks, 
int nr_disks,
 #define MDNAME "user.md.size"
 #define MDSIZE sizeof(uint64_t)
 
+/*
+ * If path is broken during initilization or not support xattr return 0. We can
+ * safely use 0 to represent failure case  because 0 space path can be
+ * considered as broken path.
+ */
 static uint64_t init_path_space(char *path)
 {
        struct statvfs fs;
        uint64_t size;
 
+       if (!is_xattr_enabled(path)) {
+               sd_iprintf("multi-disk support need xattr feature");
+               goto broken_path;
+       }
+
        if (getxattr(path, MDNAME, &size, MDSIZE) < 0) {
-               if (errno == ENODATA)
+               if (errno == ENODATA) {
                        goto create;
-               else
-                       panic("%s, %m", path);
+               } else {
+                       sd_eprintf("%s, %m", path);
+                       goto broken_path;
+               }
        }
 
        return size;
 create:
-       if (statvfs(path, &fs) < 0)
-               panic("get disk %s space failed %m", path);
+       if (statvfs(path, &fs) < 0) {
+               sd_eprintf("get disk %s space failed %m", path);
+               goto broken_path;
+       }
        size = (int64_t)fs.f_frsize * fs.f_bfree;
-       if (setxattr(path, MDNAME, &size, MDSIZE, 0) < 0)
-               panic("%s, %m", path);
+       if (setxattr(path, MDNAME, &size, MDSIZE, 0) < 0) {
+               sd_eprintf("%s, %m", path);
+               goto broken_path;
+       }
        return size;
+broken_path:
+       return 0;
+}
+
+static inline void remove_disk(int idx)
+{
+       int i;
+
+       sd_iprintf("%s from multi-disk array", md_disks[idx].path);
+       /*
+        * We need to keep last disk path to generate EIO when all disks are
+        * broken
+        */
+       for (i = idx; i < md_nr_disks - 1; i++)
+               md_disks[i] = md_disks[i + 1];
+
+       md_nr_disks--;
 }
 
 uint64_t md_init_space(void)
 {
-       uint64_t total = 0;
+       uint64_t total;
        int i;
 
+reinit:
        if (!md_nr_disks)
                return 0;
+       total = 0;
 
        for (i = 0; i < md_nr_disks; i++) {
-               if (!is_xattr_enabled(md_disks[i].path))
-                       panic("multi-disk support need xattr feature");
                md_disks[i].space = init_path_space(md_disks[i].path);
+               if (!md_disks[i].space) {
+                       remove_disk(i);
+                       goto reinit;
+               }
                total += md_disks[i].space;
        }
        calculate_vdisks(md_disks, md_nr_disks, total);
@@ -329,15 +366,8 @@ static inline void kick_recover(void)
 
 static void unplug_disk(int idx)
 {
-       int i;
 
-       /*
-        * We need to keep last disk path to generate EIO when all disks are
-        * broken
-        */
-       for (i = idx; i < md_nr_disks - 1; i++)
-               md_disks[i] = md_disks[i + 1];
-       md_nr_disks--;
+       remove_disk(idx);
        sys->disk_space = md_init_space();
        if (md_nr_disks > 0)
                kick_recover();
-- 
1.7.9.5