From 02dbfc99b424dde3cf0a492ed3bec4f222441754 Mon Sep 17 00:00:00 2001 From: Omar Sandoval Date: Fri, 20 May 2016 13:50:33 -0700 Subject: Btrfs: fix ->iterate_shared() by upgrading i_rwsem for delayed nodes Commit fe742fd4f90f ("Revert "btrfs: switch to ->iterate_shared()"") backed out the conversion to ->iterate_shared() for Btrfs because the delayed inode handling in btrfs_real_readdir() is racy. However, we can still do readdir in parallel if there are no delayed nodes. This is a temporary fix which upgrades the shared inode lock to an exclusive lock only when we have delayed items until we come up with a more complete solution. While we're here, rename the btrfs_{get,put}_delayed_items functions to make it very clear that they're just for readdir. Tested with xfstests and by doing a parallel kernel build: while make tinyconfig && make -j4 && git clean dqfx; do : done along with a bunch of parallel finds in another shell: while true; do for ((i=0; i<4; i++)); do find . >/dev/null & done wait done Signed-off-by: Omar Sandoval Signed-off-by: David Sterba Signed-off-by: Chris Mason --- fs/btrfs/inode.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) (limited to 'fs/btrfs/inode.c') diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index d2be95c..969a25c 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -5757,6 +5757,7 @@ static int btrfs_real_readdir(struct file *file, struct dir_context *ctx) int name_len; int is_curr = 0; /* ctx->pos points to the current index? */ bool emitted; + bool put = false; /* FIXME, use a real flag for deciding about the key type */ if (root->fs_info->tree_root == root) @@ -5774,7 +5775,8 @@ static int btrfs_real_readdir(struct file *file, struct dir_context *ctx) if (key_type == BTRFS_DIR_INDEX_KEY) { INIT_LIST_HEAD(&ins_list); INIT_LIST_HEAD(&del_list); - btrfs_get_delayed_items(inode, &ins_list, &del_list); + put = btrfs_readdir_get_delayed_items(inode, &ins_list, + &del_list); } key.type = key_type; @@ -5921,8 +5923,8 @@ next: nopos: ret = 0; err: - if (key_type == BTRFS_DIR_INDEX_KEY) - btrfs_put_delayed_items(&ins_list, &del_list); + if (put) + btrfs_readdir_put_delayed_items(inode, &ins_list, &del_list); btrfs_free_path(path); return ret; } @@ -10534,7 +10536,7 @@ static const struct inode_operations btrfs_dir_ro_inode_operations = { static const struct file_operations btrfs_dir_file_operations = { .llseek = generic_file_llseek, .read = generic_read_dir, - .iterate = btrfs_real_readdir, + .iterate_shared = btrfs_real_readdir, .unlocked_ioctl = btrfs_ioctl, #ifdef CONFIG_COMPAT .compat_ioctl = btrfs_compat_ioctl, -- cgit v1.1