Re: [PATCH 3/3] writeback: introduce super_operations->write_metadata
From: Jan Kara <jack@suse.cz>
Date: 2016-09-09 08:29:29
Also in:
linux-fsdevel, linux-mm
On Mon 22-08-16 13:35:02, Josef Bacik wrote:
Now that we have metadata counters in the VM, we need to provide a way to kick writeback on dirty metadata. Introduce super_operations->write_metadata. This allows file systems to deal with writing back any dirty metadata we need based on the writeback needs of the system. Since there is no inode to key off of we need a list in the bdi for dirty super blocks to be added. From there we can find any dirty sb's on the bdi we are currently doing writeback on and call into their ->write_metadata callback. Signed-off-by: Josef Bacik <redacted>
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quoted hunk ↗ jump to hunk
@@ -1639,11 +1664,38 @@ static long __writeback_inodes_wb(struct bdi_writeback *wb, /* refer to the same tests at the end of writeback_sb_inodes */ if (wrote) { - if (time_is_before_jiffies(start_time + HZ / 10UL)) - break; - if (work->nr_pages <= 0) + if (time_is_before_jiffies(start_time + HZ / 10UL) || + work->nr_pages <= 0) { + done = true; break; + } + } + } + + if (!done && wb_stat(wb, WB_METADATA_DIRTY)) { + LIST_HEAD(list); + + spin_unlock(&wb->list_lock); + spin_lock(&wb->bdi->sb_list_lock); + list_splice_init(&wb->bdi->dirty_sb_list, &list); + while (!list_empty(&list)) { + struct super_block *sb; + + sb = list_first_entry(&list, struct super_block, + s_bdi_list); + list_move_tail(&sb->s_bdi_list, + &wb->bdi->dirty_sb_list); + if (!sb->s_op->write_metadata) + continue; + if (!trylock_super(sb)) + continue; + spin_unlock(&wb->bdi->sb_list_lock); + wrote += writeback_sb_metadata(sb, wb, work); + spin_lock(&wb->bdi->sb_list_lock); + up_read(&sb->s_umount); } + spin_unlock(&wb->bdi->sb_list_lock); + spin_lock(&wb->list_lock); } /* Leave any unwritten inodes on b_io */ return wrote;
So this will hook metadata writeback into the periodic writeback but when work->sb is set, metadata won't be written because in that case we call writeback_sb_inodes() directly. So you need to call writeback_sb_metadata() from wb_writeback() in that case as well. ...
quoted hunk ↗ jump to hunk
diff --git a/include/linux/fs.h b/include/linux/fs.h index f3f0b4c8..c063ac6 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h@@ -1430,6 +1430,8 @@ struct super_block { spinlock_t s_inode_wblist_lock; struct list_head s_inodes_wb; /* writeback inodes */ + + struct list_head s_bdi_list;
Maybe call this s_bdi_dirty_list? Honza -- Jan Kara [off-list ref] SUSE Labs, CR