On Fri, Dec 11, 2020 at 1:39 PM Jeff Layton <jlayton@xxxxxxxxxx> wrote:
>
> Testing with the fscache overhaul has triggered some lockdep warnings
> about circular lock dependencies involving page_mkwrite and the
> mmap_lock. It'd be better to do the "real work" without the mmap lock
> being held.
>
> Change the skip_checking_caps parameter in __ceph_put_cap_refs to an
> enum, and use that to determine whether to queue check_caps, do it
> synchronously or not at all. Change ceph_page_mkwrite to do a
> ceph_put_cap_refs_async().
>
> Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
> ---
> fs/ceph/addr.c | 2 +-
> fs/ceph/caps.c | 28 ++++++++++++++++++++++++----
> fs/ceph/inode.c | 6 ++++++
> fs/ceph/super.h | 19 ++++++++++++++++---
> 4 files changed, 47 insertions(+), 8 deletions(-)
>
> diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
> index 950552944436..26e66436f005 100644
> --- a/fs/ceph/addr.c
> +++ b/fs/ceph/addr.c
> @@ -1662,7 +1662,7 @@ static vm_fault_t ceph_page_mkwrite(struct vm_fault *vmf)
>
> dout("page_mkwrite %p %llu~%zd dropping cap refs on %s ret %x\n",
> inode, off, len, ceph_cap_string(got), ret);
> - ceph_put_cap_refs(ci, got);
> + ceph_put_cap_refs_async(ci, got);
> out_free:
> ceph_restore_sigs(&oldset);
> sb_end_pagefault(inode->i_sb);
> diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
> index 336348e733b9..a95ab4c02056 100644
> --- a/fs/ceph/caps.c
> +++ b/fs/ceph/caps.c
> @@ -3026,6 +3026,12 @@ static int ceph_try_drop_cap_snap(struct ceph_inode_info *ci,
> return 0;
> }
>
> +enum PutCapRefsMode {
> + PutCapRefsModeSync = 0,
> + PutCapRefsModeSkip,
> + PutCapRefsModeAsync,
> +};
Hi Jeff,
A couple style nits, since mixed case stood out ;)
Let's avoid CamelCase. Page flags and existing protocol definitions
like SMB should be the only exception. I'd suggest PUT_CAP_REFS_SYNC,
etc.
> +
> /*
> * Release cap refs.
> *
> @@ -3036,7 +3042,7 @@ static int ceph_try_drop_cap_snap(struct ceph_inode_info *ci,
> * cap_snap, and wake up any waiters.
> */
> static void __ceph_put_cap_refs(struct ceph_inode_info *ci, int had,
> - bool skip_checking_caps)
> + enum PutCapRefsMode mode)
> {
> struct inode *inode = &ci->vfs_inode;
> int last = 0, put = 0, flushsnaps = 0, wake = 0;
> @@ -3092,11 +3098,20 @@ static void __ceph_put_cap_refs(struct ceph_inode_info *ci, int had,
> dout("put_cap_refs %p had %s%s%s\n", inode, ceph_cap_string(had),
> last ? " last" : "", put ? " put" : "");
>
> - if (!skip_checking_caps) {
> + switch(mode) {
> + default:
> + break;
> + case PutCapRefsModeSync:
> if (last)
> ceph_check_caps(ci, 0, NULL);
> else if (flushsnaps)
> ceph_flush_snaps(ci, NULL);
> + break;
> + case PutCapRefsModeAsync:
> + if (last)
> + ceph_queue_check_caps(inode);
> + else if (flushsnaps)
> + ceph_queue_flush_snaps(inode);
Add a break here. I'd also move the default clause to the end.
> }
> if (wake)
> wake_up_all(&ci->i_cap_wq);
> @@ -3106,12 +3121,17 @@ static void __ceph_put_cap_refs(struct ceph_inode_info *ci, int had,
>
> void ceph_put_cap_refs(struct ceph_inode_info *ci, int had)
> {
> - __ceph_put_cap_refs(ci, had, false);
> + __ceph_put_cap_refs(ci, had, PutCapRefsModeSync);
> +}
> +
> +void ceph_put_cap_refs_async(struct ceph_inode_info *ci, int had)
> +{
> + __ceph_put_cap_refs(ci, had, PutCapRefsModeAsync);
> }
>
> void ceph_put_cap_refs_no_check_caps(struct ceph_inode_info *ci, int had)
> {
> - __ceph_put_cap_refs(ci, had, true);
> + __ceph_put_cap_refs(ci, had, PutCapRefsModeSkip);
Perhaps name the enum member PUT_CAP_REFS_NO_CHECK to match the
exported function?
Thanks,
Ilya
