On Tue 25-10-11 21:04:53, Kazuya Mio wrote: > Write systemcall calls balance_dirty_pages() for direct reclaim. > However, if ext4 is aborted because of the journal abort, ext4_da_writepages() > cannot reduce the number of dirty pages because EXT4_MF_FS_ABORTED is set to > s_mount_flag. banalce_dirty_pages() has a busy loop, and we can pass this loop > only if the number of dirty pages is less than the threshold. So this function > loops infinity. > > When write systemcall and kjournald ran at the same time and the disk > corruption happened, the problem occurred. The kernel version was 3.1-rc9. > I corrupted the disk on purpose by using dmsetup command. > > > process1 (write) process2 (kjournald) > > generic_perform_write > ext4_da_write_begin > ext4_da_write_end > > -------------- detect disk corruption -------------- > > jbd2_journal_commit_transaction > journal_submit_data_buffers > jbd2_journal_abort > > balance_dirty_pages > writeback_inodes_wb > ... > ext4_da_writepages <- do nothing if EXT4_MF_FS_ABORTED is set > ext4_journal_start > ext4_journal_start_sb <- detect journal abort > ext4_abort <- set EXT4_MF_FS_ABORTED Thanks for report! > One possible idea to fix this problem is that ext4_da_writepages() > invalidates the dirty pages if the filesystem has been aborted. Please no. Generally this boils down to what do we do with dirty data when there's error in writing them out. Currently we just throw them away (e.g. in media error case) but I don't think that's a generally good thing because e.g. admin may want to copy the data to other working storage or so. So I think we should rather keep the data and provide a mechanism for userspace to ask kernel to get rid of the data (so that we don't eventually run OOM). > Do you have any ideas? So the question is what would you like to achieve. If you just want to unblock a thread then a solution would be to make a thread at balance_dirty_pages() killable. If generally you want to get rid of dirty memory, then I don't have a really good answer but throwing dirty data away seems like a bad answer to me. Honza -- Jan Kara <jack@xxxxxxx> SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
