On Tue 03-08-21 21:03:43, Amir Goldstein wrote:
> Rename s_fsnotify_inode_refs to s_fsnotify_conectors and count all
> objects with attached connectors, not only inodes with attached
> connectors.
>
> This will be used to optimize fsnotify() calls on sb without any
> type of marks.
>
> Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
> ---
> fs/notify/fsnotify.c | 6 +++---
> fs/notify/mark.c | 45 +++++++++++++++++++++++++++++++++++++++++---
> include/linux/fs.h | 4 ++--
> 3 files changed, 47 insertions(+), 8 deletions(-)
>
> diff --git a/fs/notify/fsnotify.c b/fs/notify/fsnotify.c
> index 30d422b8c0fc..a5de7f32c493 100644
> --- a/fs/notify/fsnotify.c
> +++ b/fs/notify/fsnotify.c
> @@ -87,9 +87,9 @@ static void fsnotify_unmount_inodes(struct super_block *sb)
>
> if (iput_inode)
> iput(iput_inode);
> - /* Wait for outstanding inode references from connectors */
> - wait_var_event(&sb->s_fsnotify_inode_refs,
> - !atomic_long_read(&sb->s_fsnotify_inode_refs));
> + /* Wait for outstanding object references from connectors */
> + wait_var_event(&sb->s_fsnotify_connectors,
> + !atomic_long_read(&sb->s_fsnotify_connectors));
> }
I think this is wrong and will deadlock unmount if there's pending sb mark
because s_fsnotify_connectors won't drop to 0. I think you need to move
this wait to fsnotify_sb_delete() after fsnotify_clear_marks_by_sb().
Otherwise the patch looks good to me.
Honza
>
> void fsnotify_sb_delete(struct super_block *sb)
> diff --git a/fs/notify/mark.c b/fs/notify/mark.c
> index 2d8c46e1167d..622bcbface4f 100644
> --- a/fs/notify/mark.c
> +++ b/fs/notify/mark.c
> @@ -172,7 +172,7 @@ static void fsnotify_connector_destroy_workfn(struct work_struct *work)
> static void fsnotify_get_inode_ref(struct inode *inode)
> {
> ihold(inode);
> - atomic_long_inc(&inode->i_sb->s_fsnotify_inode_refs);
> + atomic_long_inc(&inode->i_sb->s_fsnotify_connectors);
> }
>
> static void fsnotify_put_inode_ref(struct inode *inode)
> @@ -180,8 +180,45 @@ static void fsnotify_put_inode_ref(struct inode *inode)
> struct super_block *sb = inode->i_sb;
>
> iput(inode);
> - if (atomic_long_dec_and_test(&sb->s_fsnotify_inode_refs))
> - wake_up_var(&sb->s_fsnotify_inode_refs);
> + if (atomic_long_dec_and_test(&sb->s_fsnotify_connectors))
> + wake_up_var(&sb->s_fsnotify_connectors);
> +}
> +
> +static void fsnotify_get_sb_connectors(struct fsnotify_mark_connector *conn)
> +{
> + struct super_block *sb;
> +
> + if (conn->type == FSNOTIFY_OBJ_TYPE_DETACHED)
> + return;
> +
> + if (conn->type == FSNOTIFY_OBJ_TYPE_INODE)
> + sb = fsnotify_conn_inode(conn)->i_sb;
> + else if (conn->type == FSNOTIFY_OBJ_TYPE_VFSMOUNT)
> + sb = fsnotify_conn_mount(conn)->mnt.mnt_sb;
> + else if (conn->type == FSNOTIFY_OBJ_TYPE_SB)
> + sb = fsnotify_conn_sb(conn);
> +
> + atomic_long_inc(&sb->s_fsnotify_connectors);
> +}
> +
> +static void fsnotify_put_sb_connectors(struct fsnotify_mark_connector *conn)
> +{
> + struct super_block *sb;
> +
> + if (conn->type == FSNOTIFY_OBJ_TYPE_DETACHED)
> + return;
> +
> + if (conn->type == FSNOTIFY_OBJ_TYPE_INODE)
> + sb = fsnotify_conn_inode(conn)->i_sb;
> + else if (conn->type == FSNOTIFY_OBJ_TYPE_VFSMOUNT)
> + sb = fsnotify_conn_mount(conn)->mnt.mnt_sb;
> + else if (conn->type == FSNOTIFY_OBJ_TYPE_SB)
> + sb = fsnotify_conn_sb(conn);
> + else
> + return;
> +
> + if (atomic_long_dec_and_test(&sb->s_fsnotify_connectors))
> + wake_up_var(&sb->s_fsnotify_connectors);
> }
>
> static void *fsnotify_detach_connector_from_object(
> @@ -203,6 +240,7 @@ static void *fsnotify_detach_connector_from_object(
> fsnotify_conn_sb(conn)->s_fsnotify_mask = 0;
> }
>
> + fsnotify_put_sb_connectors(conn);
> rcu_assign_pointer(*(conn->obj), NULL);
> conn->obj = NULL;
> conn->type = FSNOTIFY_OBJ_TYPE_DETACHED;
> @@ -504,6 +542,7 @@ static int fsnotify_attach_connector_to_object(fsnotify_connp_t *connp,
> inode = fsnotify_conn_inode(conn);
> fsnotify_get_inode_ref(inode);
> }
> + fsnotify_get_sb_connectors(conn);
>
> /*
> * cmpxchg() provides the barrier so that readers of *connp can see
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 640574294216..d48d2018dfa4 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -1507,8 +1507,8 @@ struct super_block {
> /* Number of inodes with nlink == 0 but still referenced */
> atomic_long_t s_remove_count;
>
> - /* Pending fsnotify inode refs */
> - atomic_long_t s_fsnotify_inode_refs;
> + /* Number of inode/mount/sb objects that are being watched */
> + atomic_long_t s_fsnotify_connectors;
>
> /* Being remounted read-only */
> int s_readonly_remount;
> --
> 2.25.1
>
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
