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ext4: abort the filesystem if failed to async write metadata buffer
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@huawei.com> Suggested-by: Jan Kara <jack@suse.cz> Link: https://lore.kernel.org/r/20200620025427.1756360-2-yi.zhang@huawei.com Signed-off-by: Theodore Ts'o <tytso@mit.edu>
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@ -1603,6 +1603,9 @@ struct ext4_sb_info {
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#ifdef CONFIG_EXT4_DEBUG
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unsigned long s_simulate_fail;
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#endif
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/* Record the errseq of the backing block device */
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errseq_t s_bdev_wb_err;
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spinlock_t s_bdev_wb_lock;
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};
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static inline struct ext4_sb_info *EXT4_SB(struct super_block *sb)
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@ -195,6 +195,28 @@ static void ext4_journal_abort_handle(const char *caller, unsigned int line,
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jbd2_journal_abort_handle(handle);
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}
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static void ext4_check_bdev_write_error(struct super_block *sb)
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{
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struct address_space *mapping = sb->s_bdev->bd_inode->i_mapping;
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struct ext4_sb_info *sbi = EXT4_SB(sb);
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int err;
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/*
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* If the block device has write error flag, it may have failed to
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* async write out metadata buffers in the background. In this case,
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* we could read old data from disk and write it out again, which
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* may lead to on-disk filesystem inconsistency.
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*/
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if (errseq_check(&mapping->wb_err, READ_ONCE(sbi->s_bdev_wb_err))) {
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spin_lock(&sbi->s_bdev_wb_lock);
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err = errseq_check_and_advance(&mapping->wb_err, &sbi->s_bdev_wb_err);
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spin_unlock(&sbi->s_bdev_wb_lock);
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if (err)
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ext4_error_err(sb, -err,
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"Error while async write back metadata");
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}
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}
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int __ext4_journal_get_write_access(const char *where, unsigned int line,
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handle_t *handle, struct buffer_head *bh)
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{
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@ -202,6 +224,9 @@ int __ext4_journal_get_write_access(const char *where, unsigned int line,
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might_sleep();
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if (bh->b_bdev->bd_super)
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ext4_check_bdev_write_error(bh->b_bdev->bd_super);
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if (ext4_handle_valid(handle)) {
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err = jbd2_journal_get_write_access(handle, bh);
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if (err)
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@ -4765,6 +4765,15 @@ no_journal:
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}
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#endif /* CONFIG_QUOTA */
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/*
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* Save the original bdev mapping's wb_err value which could be
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* used to detect the metadata async write error.
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*/
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spin_lock_init(&sbi->s_bdev_wb_lock);
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if (!sb_rdonly(sb))
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errseq_check_and_advance(&sb->s_bdev->bd_inode->i_mapping->wb_err,
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&sbi->s_bdev_wb_err);
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sb->s_bdev->bd_super = sb;
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EXT4_SB(sb)->s_mount_state |= EXT4_ORPHAN_FS;
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ext4_orphan_cleanup(sb, es);
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EXT4_SB(sb)->s_mount_state &= ~EXT4_ORPHAN_FS;
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@ -5654,6 +5663,14 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
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goto restore_opts;
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}
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/*
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* Update the original bdev mapping's wb_err value
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* which could be used to detect the metadata async
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* write error.
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*/
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errseq_check_and_advance(&sb->s_bdev->bd_inode->i_mapping->wb_err,
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&sbi->s_bdev_wb_err);
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/*
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* Mounting a RDONLY partition read-write, so reread
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* and store the current valid flag. (It may have
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