exofs: Write sbi->s_nextid as part of the Create command

Before when creating a new inode, we'd set the sb->s_dirt flag,
and sometime later the system would write out s_nextid as part
of the sb_info. Also on inode sync we would force the sb sync
as well.

Define the s_nextid as a new partition attribute and set it
every time we create a new object.
At mount we read it from it's new place.

We now never set sb->s_dirt anywhere in exofs. write_super
is actually never called. The call to exofs_write_super from
exofs_put_super is also removed because the VFS always calls
->sync_fs before calling ->put_super twice.

To stay backward-and-forward compatible we also write the old
s_nextid in the super_block object at unmount, and support zero
length attribute on mount.

This also fixes a BUG where in layouts when group_width was not
a divisor of EXOFS_SUPER_ID (0x10000) the s_nextid was not read
from the device it was written to. Because of the sliding window
layout trick, and because the read was always done from the 0
device but the write was done via the raid engine that might slide
the device view. Now we read and write through the raid engine.

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

1 files changed, 119 insertions, 16 deletions

diff --git a/fs/exofs/super.c b/fs/exofs/super.c
index 474989eeb7d6..5eb0851e5481 100644
--- a/fs/exofs/super.c
+++ b/fs/exofs/super.c
@@ -213,6 +213,101 @@ static void destroy_inodecache(void)
 static const struct super_operations exofs_sops;
 static const struct export_operations exofs_export_ops;
 
+static const struct osd_attr g_attr_sb_stats = ATTR_DEF(
+        EXOFS_APAGE_SB_DATA,
+        EXOFS_ATTR_SB_STATS,
+        sizeof(struct exofs_sb_stats));
+
+static int __sbi_read_stats(struct exofs_sb_info *sbi)
+{
+        struct osd_attr attrs[] = {
+                [0] = g_attr_sb_stats,
+        };
+        struct exofs_io_state *ios;
+        int ret;
+
+        ret = exofs_get_io_state(&sbi->layout, &ios);
+        if (unlikely(ret)) {
+                EXOFS_ERR("%s: exofs_get_io_state failed.\n", __func__);
+                return ret;
+        }
+
+        ios->cred = sbi->s_cred;
+
+        ios->in_attr = attrs;
+        ios->in_attr_len = ARRAY_SIZE(attrs);
+
+        ret = exofs_sbi_read(ios);
+        if (unlikely(ret)) {
+                EXOFS_ERR("Error reading super_block stats => %d\n", ret);
+                goto out;
+        }
+
+        ret = extract_attr_from_ios(ios, &attrs[0]);
+        if (ret) {
+                EXOFS_ERR("%s: extract_attr of sb_stats failed\n", __func__);
+                goto out;
+        }
+        if (attrs[0].len) {
+                struct exofs_sb_stats *ess;
+
+                if (unlikely(attrs[0].len != sizeof(*ess))) {
+                        EXOFS_ERR("%s: Wrong version of exofs_sb_stats "
+                                  "size(%d) != expected(%zd)\n",
+                                  __func__, attrs[0].len, sizeof(*ess));
+                        goto out;
+                }
+
+                ess = attrs[0].val_ptr;
+                sbi->s_nextid = le64_to_cpu(ess->s_nextid);
+                sbi->s_numfiles = le32_to_cpu(ess->s_numfiles);
+        }
+
+out:
+        exofs_put_io_state(ios);
+        return ret;
+}
+
+static void stats_done(struct exofs_io_state *ios, void *p)
+{
+        exofs_put_io_state(ios);
+        /* Good thanks nothing to do anymore */
+}
+
+/* Asynchronously write the stats attribute */
+int exofs_sbi_write_stats(struct exofs_sb_info *sbi)
+{
+        struct osd_attr attrs[] = {
+                [0] = g_attr_sb_stats,
+        };
+        struct exofs_io_state *ios;
+        int ret;
+
+        ret = exofs_get_io_state(&sbi->layout, &ios);
+        if (unlikely(ret)) {
+                EXOFS_ERR("%s: exofs_get_io_state failed.\n", __func__);
+                return ret;
+        }
+
+        sbi->s_ess.s_nextid   = cpu_to_le64(sbi->s_nextid);
+        sbi->s_ess.s_numfiles = cpu_to_le64(sbi->s_numfiles);
+        attrs[0].val_ptr = &sbi->s_ess;
+
+        ios->cred = sbi->s_cred;
+        ios->done = stats_done;
+        ios->private = sbi;
+        ios->out_attr = attrs;
+        ios->out_attr_len = ARRAY_SIZE(attrs);
+
+        ret = exofs_sbi_write(ios);
+        if (unlikely(ret)) {
+                EXOFS_ERR("%s: exofs_sbi_write failed.\n", __func__);
+                exofs_put_io_state(ios);
+        }
+
+        return ret;
+}
+
 /*
  * Write the superblock to the OSD
  */
@@ -223,18 +318,25 @@ int exofs_sync_fs(struct super_block *sb, int wait)
         struct exofs_io_state *ios;
         int ret = -ENOMEM;
 
-        lock_super(sb);
+        fscb = kmalloc(sizeof(*fscb), GFP_KERNEL);
+        if (unlikely(!fscb))
+                return -ENOMEM;
+
         sbi = sb->s_fs_info;
-        fscb = &sbi->s_fscb;
 
+        /* NOTE: We no longer dirty the super_block anywhere in exofs. The
+         * reason we write the fscb here on unmount is so we can stay backwards
+         * compatible with fscb->s_version == 1. (What we are not compatible
+         * with is if a new version FS crashed and then we try to mount an old
+         * version). Otherwise the exofs_fscb is read-only from mkfs time. All
+         * the writeable info is set in exofs_sbi_write_stats() above.
+         */
         ret = exofs_get_io_state(&sbi->layout, &ios);
-        if (ret)
+        if (unlikely(ret))
                 goto out;
 
-        /* Note: We only write the changing part of the fscb. .i.e upto the
-         *       the fscb->s_dev_table_oid member. There is no read-modify-write
-         *       here.
-         */
+        lock_super(sb);
+
         ios->length = offsetof(struct exofs_fscb, s_dev_table_oid);
         memset(fscb, 0, ios->length);
         fscb->s_nextid = cpu_to_le64(sbi->s_nextid);
@@ -249,16 +351,17 @@ int exofs_sync_fs(struct super_block *sb, int wait)
         ios->cred = sbi->s_cred;
 
         ret = exofs_sbi_write(ios);
-        if (unlikely(ret)) {
+        if (unlikely(ret))
                 EXOFS_ERR("%s: exofs_sbi_write failed.\n", __func__);
-                goto out;
-        }
-        sb->s_dirt = 0;
+        else
+                sb->s_dirt = 0;
 
+
+        unlock_super(sb);
 out:
         EXOFS_DBGMSG("s_nextid=0x%llx ret=%d\n", _LLU(sbi->s_nextid), ret);
         exofs_put_io_state(ios);
-        unlock_super(sb);
+        kfree(fscb);
         return ret;
 }
 
@@ -302,9 +405,6 @@ static void exofs_put_super(struct super_block *sb)
         int num_pend;
         struct exofs_sb_info *sbi = sb->s_fs_info;
 
-        if (sb->s_dirt)
-                exofs_write_super(sb);
-
         /* make sure there are no pending commands */
         for (num_pend = atomic_read(&sbi->s_curr_pending); num_pend > 0;
              num_pend = atomic_read(&sbi->s_curr_pending)) {
@@ -629,6 +729,7 @@ static int exofs_fill_super(struct super_block *sb, void *data, int silent)
                 goto free_sbi;
 
         sb->s_magic = le16_to_cpu(fscb.s_magic);
+        /* NOTE: we read below to be backward compatible with old versions */
         sbi->s_nextid = le64_to_cpu(fscb.s_nextid);
         sbi->s_numfiles = le32_to_cpu(fscb.s_numfiles);
 
@@ -639,7 +740,7 @@ static int exofs_fill_super(struct super_block *sb, void *data, int silent)
                 ret = -EINVAL;
                 goto free_sbi;
         }
-        if (le32_to_cpu(fscb.s_version) != EXOFS_FSCB_VER) {
+        if (le32_to_cpu(fscb.s_version) > EXOFS_FSCB_VER) {
                 EXOFS_ERR("ERROR: Bad FSCB version expected-%d got-%d\n",
                           EXOFS_FSCB_VER, le32_to_cpu(fscb.s_version));
                 ret = -EINVAL;
@@ -657,6 +758,8 @@ static int exofs_fill_super(struct super_block *sb, void *data, int silent)
                         goto free_sbi;
         }
 
+        __sbi_read_stats(sbi);
+
         /* set up operation vectors */
         sbi->bdi.ra_pages = __ra_pages(&sbi->layout);
         sb->s_bdi = &sbi->bdi;