On Wed, 28 Nov 2012 18:23:44 +0400
Pavel Shilovsky <piastry@xxxxxxxxxxx> wrote:
> We don't need to permit a write to the area locked with a read lock
> by any process including the process that issues the write.
>
> Signed-off-by: Pavel Shilovsky <piastry@xxxxxxxxxxx>
> ---
> fs/cifs/cifsproto.h | 2 +-
> fs/cifs/file.c | 27 ++++++++++++++++++---------
> 2 files changed, 19 insertions(+), 10 deletions(-)
>
> diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h
> index 7e1562d..4883f95 100644
> --- a/fs/cifs/cifsproto.h
> +++ b/fs/cifs/cifsproto.h
> @@ -187,7 +187,7 @@ extern void cifs_mark_open_files_invalid(struct cifs_tcon *tcon);
> extern bool cifs_find_lock_conflict(struct cifsFileInfo *cfile, __u64 offset,
> __u64 length, __u8 type,
> struct cifsLockInfo **conf_lock,
> - bool rw_check);
> + int rw_check);
> extern void cifs_add_pending_open(struct cifs_fid *fid,
> struct tcon_link *tlink,
> struct cifs_pending_open *open);
> diff --git a/fs/cifs/file.c b/fs/cifs/file.c
> index f8fe1bd..e7fc39c 100644
> --- a/fs/cifs/file.c
> +++ b/fs/cifs/file.c
> @@ -765,10 +765,15 @@ cifs_del_lock_waiters(struct cifsLockInfo *lock)
> }
> }
>
> +#define CIFS_LOCK_OP 0
> +#define CIFS_READ_OP 1
> +#define CIFS_WRITE_OP 2
> +
> +/* @rw_check : 0 - no op, 1 - read, 2 - write */
> static bool
> cifs_find_fid_lock_conflict(struct cifs_fid_locks *fdlocks, __u64 offset,
> __u64 length, __u8 type, struct cifsFileInfo *cfile,
> - struct cifsLockInfo **conf_lock, bool rw_check)
> + struct cifsLockInfo **conf_lock, int rw_check)
> {
> struct cifsLockInfo *li;
> struct cifsFileInfo *cur_cfile = fdlocks->cfile;
> @@ -778,9 +783,13 @@ cifs_find_fid_lock_conflict(struct cifs_fid_locks *fdlocks, __u64 offset,
> if (offset + length <= li->offset ||
> offset >= li->offset + li->length)
> continue;
> - if (rw_check && server->ops->compare_fids(cfile, cur_cfile) &&
> - current->tgid == li->pid)
> - continue;
> + if (rw_check != CIFS_LOCK_OP && current->tgid == li->pid &&
> + server->ops->compare_fids(cfile, cur_cfile)) {
> + /* shared lock prevents write op through the same fid */
> + if (!(li->type & server->vals->shared_lock_type) ||
> + rw_check != CIFS_WRITE_OP)
> + continue;
> + }
> if ((type & server->vals->shared_lock_type) &&
> ((server->ops->compare_fids(cfile, cur_cfile) &&
> current->tgid == li->pid) || type == li->type))
> @@ -795,7 +804,7 @@ cifs_find_fid_lock_conflict(struct cifs_fid_locks *fdlocks, __u64 offset,
> bool
> cifs_find_lock_conflict(struct cifsFileInfo *cfile, __u64 offset, __u64 length,
> __u8 type, struct cifsLockInfo **conf_lock,
> - bool rw_check)
> + int rw_check)
> {
> bool rc = false;
> struct cifs_fid_locks *cur;
> @@ -831,7 +840,7 @@ cifs_lock_test(struct cifsFileInfo *cfile, __u64 offset, __u64 length,
> down_read(&cinode->lock_sem);
>
> exist = cifs_find_lock_conflict(cfile, offset, length, type,
> - &conf_lock, false);
> + &conf_lock, CIFS_LOCK_OP);
> if (exist) {
> flock->fl_start = conf_lock->offset;
> flock->fl_end = conf_lock->offset + conf_lock->length - 1;
> @@ -878,7 +887,7 @@ try_again:
> down_write(&cinode->lock_sem);
>
> exist = cifs_find_lock_conflict(cfile, lock->offset, lock->length,
> - lock->type, &conf_lock, false);
> + lock->type, &conf_lock, CIFS_LOCK_OP);
> if (!exist && cinode->can_cache_brlcks) {
> list_add_tail(&lock->llist, &cfile->llist->locks);
> up_write(&cinode->lock_sem);
> @@ -2472,7 +2481,7 @@ cifs_writev(struct kiocb *iocb, const struct iovec *iov,
> down_read(&cinode->lock_sem);
> if (!cifs_find_lock_conflict(cfile, pos, iov_length(iov, nr_segs),
> server->vals->exclusive_lock_type, NULL,
> - true)) {
> + CIFS_WRITE_OP)) {
> mutex_lock(&inode->i_mutex);
> rc = __generic_file_aio_write(iocb, iov, nr_segs,
> &iocb->ki_pos);
> @@ -2907,7 +2916,7 @@ cifs_strict_readv(struct kiocb *iocb, const struct iovec *iov,
> down_read(&cinode->lock_sem);
> if (!cifs_find_lock_conflict(cfile, pos, iov_length(iov, nr_segs),
> tcon->ses->server->vals->shared_lock_type,
> - NULL, true))
> + NULL, CIFS_READ_OP))
> rc = generic_file_aio_read(iocb, iov, nr_segs, pos);
> up_read(&cinode->lock_sem);
> return rc;
Code looks ok I guess. I'll have to take your word for it that the
windows locking semantics here are correct though...
Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
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