Re: [PATCH] btrfs: remove unnecessary btrfs_delalloc_release_metadata() call
From: Filipe Manana <hidden>
Date: 2016-05-19 10:29:49
On Thu, May 19, 2016 at 10:44 AM, Wang Xiaoguang [off-list ref] wrote:
In __btrfs_write_out_cache(), we don't call btrfs_delalloc_reserve_metadata() or btrfs_delalloc_reserve_space() to reserve metadata space, so we also should not call btrfs_delalloc_release_metadata(), in which BTRFS_I(inode)->outstanding_extents will be decreased, then WARN_ON(BTRFS_I(inode)->outstanding_extents) in btrfs_destroy_inode() will be triggered. To be honest, I do not see this WARNING in real, but I think we should fix it.
No, this is wrong. We do this call to release reserved metadata space at btrfs_save_ino_cache() through btrfs_delalloc_reserve_space(). And it's btrfs_save_ino_cache() that calls btrfs_write_out_ino_cache(). If what you said were true, then it would be trivial to write a test case (using the inode cache feature) to trigger the problem.
quoted hunk ↗ jump to hunk
Signed-off-by: Wang Xiaoguang <redacted> --- fs/btrfs/free-space-cache.c | 17 +++-------------- 1 file changed, 3 insertions(+), 14 deletions(-)diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c index 8f835bf..ababf56 100644 --- a/fs/btrfs/free-space-cache.c +++ b/fs/btrfs/free-space-cache.c@@ -3512,7 +3512,6 @@ int btrfs_write_out_ino_cache(struct btrfs_root *root, struct btrfs_free_space_ctl *ctl = root->free_ino_ctl; int ret; struct btrfs_io_ctl io_ctl; - bool release_metadata = true; if (!btrfs_test_opt(root, INODE_MAP_CACHE)) return 0;@@ -3520,26 +3519,16 @@ int btrfs_write_out_ino_cache(struct btrfs_root *root, memset(&io_ctl, 0, sizeof(io_ctl)); ret = __btrfs_write_out_cache(root, inode, ctl, NULL, &io_ctl, trans, path, 0); - if (!ret) { - /* - * At this point writepages() didn't error out, so our metadata - * reservation is released when the writeback finishes, at - * inode.c:btrfs_finish_ordered_io(), regardless of it finishing - * with or without an error. - */ - release_metadata = false; + if (!ret) ret = btrfs_wait_cache_io(root, trans, NULL, &io_ctl, path, 0); - } - if (ret) { - if (release_metadata) - btrfs_delalloc_release_metadata(inode, inode->i_size); #ifdef DEBUG + if (ret) { btrfs_err(root->fs_info, "failed to write free ino cache for root %llu", root->root_key.objectid); -#endif } +#endif return ret; } --1.8.3.1 -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
-- Filipe David Manana, "Reasonable men adapt themselves to the world. Unreasonable men adapt the world to themselves. That's why all progress depends on unreasonable men."