| Message ID | 1526406728-109055-6-git-send-email-bo.liu@linux.alibaba.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 15.05.2018 20:52, Liu Bo wrote: > In case of (cow && (p->keep_locks || p->lowest_level)), write_lock_level > is the max level, and we should grab write lock of root node from the very > beginning. THis needs to be expanded to explain what are the adverse effects (if any) without this commit. And then explain how this commit actually improve things. > > Signed-off-by: Liu Bo <bo.liu@linux.alibaba.com> > --- > fs/btrfs/ctree.c | 29 ++++++++++++++++------------- > 1 file changed, 16 insertions(+), 13 deletions(-) > > diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c > index cf34eca41d4e..f7c3f581f647 100644 > --- a/fs/btrfs/ctree.c > +++ b/fs/btrfs/ctree.c > @@ -2633,20 +2633,23 @@ static struct extent_buffer *btrfs_search_slot_get_root(struct btrfs_root *root, > goto out; > } > > - /* > - * we don't know the level of the root node until we actually > - * have it read locked > - */ > - b = btrfs_read_lock_root_node(root); > - level = btrfs_header_level(b); > - if (level > write_lock_level) > - goto out; > + if (write_lock_level < BTRFS_MAX_LEVEL) { > + /* > + * we don't know the level of the root node until we actually > + * have it read locked > + */ > + b = btrfs_read_lock_root_node(root); > + level = btrfs_header_level(b); > + if (level > write_lock_level) > + goto out; > + > + /* > + * whoops, must trade for write lock > + */ > + btrfs_tree_read_unlock(b); > + free_extent_buffer(b); > + } Here just seems you are adding 1 extra branch so more context please. > > - /* > - * whoops, must trade for write lock > - */ > - btrfs_tree_read_unlock(b); > - free_extent_buffer(b); > b = btrfs_lock_root_node(root); > root_lock = BTRFS_WRITE_LOCK; > /* > -- 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
diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c index cf34eca41d4e..f7c3f581f647 100644 --- a/fs/btrfs/ctree.c +++ b/fs/btrfs/ctree.c @@ -2633,20 +2633,23 @@ static struct extent_buffer *btrfs_search_slot_get_root(struct btrfs_root *root, goto out; } - /* - * we don't know the level of the root node until we actually - * have it read locked - */ - b = btrfs_read_lock_root_node(root); - level = btrfs_header_level(b); - if (level > write_lock_level) - goto out; + if (write_lock_level < BTRFS_MAX_LEVEL) { + /* + * we don't know the level of the root node until we actually + * have it read locked + */ + b = btrfs_read_lock_root_node(root); + level = btrfs_header_level(b); + if (level > write_lock_level) + goto out; + + /* + * whoops, must trade for write lock + */ + btrfs_tree_read_unlock(b); + free_extent_buffer(b); + } - /* - * whoops, must trade for write lock - */ - btrfs_tree_read_unlock(b); - free_extent_buffer(b); b = btrfs_lock_root_node(root); root_lock = BTRFS_WRITE_LOCK; /*
In case of (cow && (p->keep_locks || p->lowest_level)), write_lock_level is the max level, and we should grab write lock of root node from the very beginning. Signed-off-by: Liu Bo <bo.liu@linux.alibaba.com> --- fs/btrfs/ctree.c | 29 ++++++++++++++++------------- 1 file changed, 16 insertions(+), 13 deletions(-)