Add the FS_WB_ERRSEQ flag to indicate to other subsystems that errseq_t
based error reporting for data writeback is in effect, and to opt-in to
reporting those errors in call_fsync.

ext4 uses the blockdev mapping for tracking metadata stored in the
pagecache. Sample its wb_err when opening a file and store that in
the f_md_wb_err field. Ensure that we check and advance the metadata
before returning in fsync.

Note that because metadata writeback errors are only tracked on a
per-device level, this does mean that we'll end up reporting an error on
all open file descriptors on this fs when there is a metadata writeback
failure.  That's not ideal, but we can possibly improve upon it in the
future.

ext4 also has several calls to filemap_fdatawait and
filemap_write_and_wait. Those will also be changed in a later patch to
versions that use errseq_t based reporting.

Signed-off-by: Jeff Layton <jlay...@redhat.com>
---
 fs/ext4/dir.c   |  8 ++++++--
 fs/ext4/file.c  |  5 ++++-
 fs/ext4/fsync.c | 23 +++++++++++++++++++----
 fs/ext4/super.c |  6 +++---
 4 files changed, 32 insertions(+), 10 deletions(-)

diff --git a/fs/ext4/dir.c b/fs/ext4/dir.c
index e8b365000d73..6bbb19510f74 100644
--- a/fs/ext4/dir.c
+++ b/fs/ext4/dir.c
@@ -611,9 +611,13 @@ static int ext4_dx_readdir(struct file *file, struct 
dir_context *ctx)
 
 static int ext4_dir_open(struct inode * inode, struct file * filp)
 {
+       int ret = 0;
+
        if (ext4_encrypted_inode(inode))
-               return fscrypt_get_encryption_info(inode) ? -EACCES : 0;
-       return 0;
+               ret = fscrypt_get_encryption_info(inode) ? -EACCES : 0;
+       if (!ret)
+               filp->f_md_wb_err = 
filemap_sample_wb_err(inode->i_sb->s_bdev->bd_inode->i_mapping);
+       return ret;
 }
 
 static int ext4_release_dir(struct inode *inode, struct file *filp)
diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 02ce7e7bbdf5..6e505269132c 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -435,7 +435,10 @@ static int ext4_file_open(struct inode * inode, struct 
file * filp)
                if (ret < 0)
                        return ret;
        }
-       return dquot_file_open(inode, filp);
+       ret = dquot_file_open(inode, filp);
+       if (!ret)
+               filp->f_md_wb_err = 
filemap_sample_wb_err(sb->s_bdev->bd_inode->i_mapping);
+       return ret;
 }
 
 /*
diff --git a/fs/ext4/fsync.c b/fs/ext4/fsync.c
index 9d549608fd30..09e28b7fd3f6 100644
--- a/fs/ext4/fsync.c
+++ b/fs/ext4/fsync.c
@@ -100,8 +100,10 @@ int ext4_sync_file(struct file *file, loff_t start, loff_t 
end, int datasync)
        tid_t commit_tid;
        bool needs_barrier = false;
 
-       if (unlikely(ext4_forced_shutdown(EXT4_SB(inode->i_sb))))
-               return -EIO;
+       if (unlikely(ext4_forced_shutdown(EXT4_SB(inode->i_sb)))) {
+               ret = -EIO;
+               goto out;
+       }
 
        J_ASSERT(ext4_journal_current_handle() == NULL);
 
@@ -126,7 +128,8 @@ int ext4_sync_file(struct file *file, loff_t start, loff_t 
end, int datasync)
 
        ret = filemap_write_and_wait_range(inode->i_mapping, start, end);
        if (ret)
-               return ret;
+               goto out;
+
        /*
         * data=writeback,ordered:
         *  The caller's filemap_fdatawrite()/wait will sync the data.
@@ -152,12 +155,24 @@ int ext4_sync_file(struct file *file, loff_t start, 
loff_t end, int datasync)
                needs_barrier = true;
        ret = jbd2_complete_transaction(journal, commit_tid);
        if (needs_barrier) {
-       issue_flush:
+issue_flush:
                err = blkdev_issue_flush(inode->i_sb->s_bdev, GFP_KERNEL, NULL);
                if (!ret)
                        ret = err;
        }
 out:
+       /*
+        * Was there a metadata writeback error since last fsync?
+        *
+        * FIXME: ext4 tracks metadata with a whole-block device mapping. So,
+        * if there is any sort of metadata writeback error, we'll report an
+        * error on all open fds, even ones not associated with the inode
+        */
+       err = filemap_report_md_wb_err(file,
+                               inode->i_sb->s_bdev->bd_inode->i_mapping);
+       if (!ret)
+               ret = err;
+
        trace_ext4_sync_file_exit(inode, ret);
        return ret;
 }
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index d37c81f327e7..e98791ebee6f 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -119,7 +119,7 @@ static struct file_system_type ext2_fs_type = {
        .name           = "ext2",
        .mount          = ext4_mount,
        .kill_sb        = kill_block_super,
-       .fs_flags       = FS_REQUIRES_DEV,
+       .fs_flags       = FS_REQUIRES_DEV|FS_WB_ERRSEQ,
 };
 MODULE_ALIAS_FS("ext2");
 MODULE_ALIAS("ext2");
@@ -134,7 +134,7 @@ static struct file_system_type ext3_fs_type = {
        .name           = "ext3",
        .mount          = ext4_mount,
        .kill_sb        = kill_block_super,
-       .fs_flags       = FS_REQUIRES_DEV,
+       .fs_flags       = FS_REQUIRES_DEV|FS_WB_ERRSEQ,
 };
 MODULE_ALIAS_FS("ext3");
 MODULE_ALIAS("ext3");
@@ -5689,7 +5689,7 @@ static struct file_system_type ext4_fs_type = {
        .name           = "ext4",
        .mount          = ext4_mount,
        .kill_sb        = kill_block_super,
-       .fs_flags       = FS_REQUIRES_DEV,
+       .fs_flags       = FS_REQUIRES_DEV|FS_WB_ERRSEQ,
 };
 MODULE_ALIAS_FS("ext4");
 
-- 
2.13.0

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