There is a risk of filesystem inconsistency if we failed to async write
back metadata buffer in the background. Because of current buffer's end
io procedure is handled by end_buffer_async_write() in the block layer,
and it only clear the buffer's uptodate flag and mark the write_io_error
flag, so ext4 cannot detect such failure immediately. In most cases of
getting metadata buffer (e.g. ext4_read_inode_bitmap()), although the
buffer's data is actually uptodate, it may still read data from disk
because the buffer's uptodate flag has been cleared. Finally, it may
lead to on-disk filesystem inconsistency if reading old data from the
disk successfully and write them out again.
This patch detect bdev mapping->wb_err when getting journal's write
access and mark the filesystem error if bdev's mapping->wb_err was
increased, this could prevent further writing and potential
inconsistency.
Signed-off-by: zhangyi (F) <yi.zhang@xxxxxxxxxx>
Suggested-by: Jan Kara <jack@xxxxxxx>
---
fs/ext4/ext4.h | 3 +++
fs/ext4/ext4_jbd2.c | 25 +++++++++++++++++++++++++
fs/ext4/super.c | 17 +++++++++++++++++
3 files changed, 45 insertions(+)
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index b08841f70b69..60374eda1f51 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1573,6 +1573,9 @@ struct ext4_sb_info {
#ifdef CONFIG_EXT4_DEBUG
unsigned long s_simulate_fail;
#endif
+ /* Record the errseq of the backing block device */
+ errseq_t s_bdev_wb_err;
+ spinlock_t s_bdev_wb_lock;
};
static inline struct ext4_sb_info *EXT4_SB(struct super_block *sb)
diff --git a/fs/ext4/ext4_jbd2.c b/fs/ext4/ext4_jbd2.c
index 0c76cdd44d90..760b9ee49dc0 100644
--- a/fs/ext4/ext4_jbd2.c
+++ b/fs/ext4/ext4_jbd2.c
@@ -195,6 +195,28 @@ static void ext4_journal_abort_handle(const char *caller, unsigned int line,
jbd2_journal_abort_handle(handle);
}
+static void ext4_check_bdev_write_error(struct super_block *sb)
+{
+ struct address_space *mapping = sb->s_bdev->bd_inode->i_mapping;
+ struct ext4_sb_info *sbi = EXT4_SB(sb);
+ int err;
+
+ /*
+ * If the block device has write error flag, it may have failed to
+ * async write out metadata buffers in the background. In this case,
+ * we could read old data from disk and write it out again, which
+ * may lead to on-disk filesystem inconsistency.
+ */
+ if (errseq_check(&mapping->wb_err, READ_ONCE(sbi->s_bdev_wb_err))) {
+ spin_lock(&sbi->s_bdev_wb_lock);
+ err = errseq_check_and_advance(&mapping->wb_err, &sbi->s_bdev_wb_err);
+ spin_unlock(&sbi->s_bdev_wb_lock);
+ if (err)
+ ext4_error_err(sb, -err,
+ "Error while async write back metadata");
+ }
+}
+
int __ext4_journal_get_write_access(const char *where, unsigned int line,
handle_t *handle, struct buffer_head *bh)
{
@@ -202,6 +224,9 @@ int __ext4_journal_get_write_access(const char *where, unsigned int line,
might_sleep();
+ if (bh->b_bdev->bd_super)
+ ext4_check_bdev_write_error(bh->b_bdev->bd_super);
+
if (ext4_handle_valid(handle)) {
err = jbd2_journal_get_write_access(handle, bh);
if (err)
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index c668f6b42374..8d3925c31b8a 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -4699,6 +4699,15 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
}
#endif /* CONFIG_QUOTA */
+ /*
+ * Save the original bdev mapping's wb_err value which could be
+ * used to detect the metadata async write error.
+ */
+ spin_lock_init(&sbi->s_bdev_wb_lock);
+ if (!sb_rdonly(sb))
+ errseq_check_and_advance(&sb->s_bdev->bd_inode->i_mapping->wb_err,
+ &sbi->s_bdev_wb_err);
+ sb->s_bdev->bd_super = sb;
EXT4_SB(sb)->s_mount_state |= EXT4_ORPHAN_FS;
ext4_orphan_cleanup(sb, es);
EXT4_SB(sb)->s_mount_state &= ~EXT4_ORPHAN_FS;
@@ -5562,6 +5571,14 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
goto restore_opts;
}
+ /*
+ * Update the original bdev mapping's wb_err value
+ * which could be used to detect the metadata async
+ * write error.
+ */
+ errseq_check_and_advance(&sb->s_bdev->bd_inode->i_mapping->wb_err,
+ &sbi->s_bdev_wb_err);
+
/*
* Mounting a RDONLY partition read-write, so reread
* and store the current valid flag. (It may have
--
2.25.4
