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    SubjectRe: [Ocfs2-devel] [PATCH 1/3] ocfs2: add ocfs2_try_rw_lock and ocfs2_try_inode_lock
    Date
    Hi Gang,

    On 2017/11/27 17:48, Gang He wrote:
    > Add ocfs2_try_rw_lock and ocfs2_try_inode_lock functions, which
    > will be used in non-block IO scenarios.
    >
    > Signed-off-by: Gang He <ghe@suse.com>
    > ---
    > fs/ocfs2/dlmglue.c | 22 ++++++++++++++++++++++
    > fs/ocfs2/dlmglue.h | 4 ++++
    > 2 files changed, 26 insertions(+)
    >
    > diff --git a/fs/ocfs2/dlmglue.c b/fs/ocfs2/dlmglue.c
    > index 4689940..5cfbd04 100644
    > --- a/fs/ocfs2/dlmglue.c
    > +++ b/fs/ocfs2/dlmglue.c
    > @@ -1742,6 +1742,28 @@ int ocfs2_rw_lock(struct inode *inode, int write)
    > return status;
    > }
    >
    > +int ocfs2_try_rw_lock(struct inode *inode, int write)
    > +{
    > + int status, level;
    > + struct ocfs2_lock_res *lockres;
    > + struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
    > +
    > + mlog(0, "inode %llu try to take %s RW lock\n",
    > + (unsigned long long)OCFS2_I(inode)->ip_blkno,
    > + write ? "EXMODE" : "PRMODE");
    > +
    > + if (ocfs2_mount_local(osb))
    > + return 0;
    > +
    > + lockres = &OCFS2_I(inode)->ip_rw_lockres;
    > +
    > + level = write ? DLM_LOCK_EX : DLM_LOCK_PR;
    > +
    > + status = ocfs2_cluster_lock(OCFS2_SB(inode->i_sb), lockres, level,
    > + DLM_LKF_NOQUEUE, 0);
    > + return status;
    > +}

    The newly added function ocfs2_try_rw_lock almost has the same logic
    with ocfs2_rw_lock.Is it possible to combine them into an unique one?
    That will be more elegant.

    Moreover, can you elaborate further why we need a *NOQUEUE* lock for
    supporting non-block aio?

    Why can't we wait for a while to grant a lock request? Is this necessary?

    Thanks,
    Changwei

    > +
    > void ocfs2_rw_unlock(struct inode *inode, int write)
    > {
    > int level = write ? DLM_LOCK_EX : DLM_LOCK_PR;
    > diff --git a/fs/ocfs2/dlmglue.h b/fs/ocfs2/dlmglue.h
    > index a7fc18b..05910fc 100644
    > --- a/fs/ocfs2/dlmglue.h
    > +++ b/fs/ocfs2/dlmglue.h
    > @@ -116,6 +116,7 @@ void ocfs2_refcount_lock_res_init(struct ocfs2_lock_res *lockres,
    > int ocfs2_create_new_inode_locks(struct inode *inode);
    > int ocfs2_drop_inode_locks(struct inode *inode);
    > int ocfs2_rw_lock(struct inode *inode, int write);
    > +int ocfs2_try_rw_lock(struct inode *inode, int write);
    > void ocfs2_rw_unlock(struct inode *inode, int write);
    > int ocfs2_open_lock(struct inode *inode);
    > int ocfs2_try_open_lock(struct inode *inode, int write);
    > @@ -140,6 +141,9 @@ int ocfs2_inode_lock_with_page(struct inode *inode,
    > /* 99% of the time we don't want to supply any additional flags --
    > * those are for very specific cases only. */
    > #define ocfs2_inode_lock(i, b, e) ocfs2_inode_lock_full_nested(i, b, e, 0, OI_LS_NORMAL)
    > +#define ocfs2_try_inode_lock(i, b, e)\
    > + ocfs2_inode_lock_full_nested(i, b, e, OCFS2_META_LOCK_NOQUEUE,\
    > + OI_LS_NORMAL)
    > void ocfs2_inode_unlock(struct inode *inode,
    > int ex);
    > int ocfs2_super_lock(struct ocfs2_super *osb,
    >

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