On Wed, 17 Nov 2010 23:53:34 +0530
Suresh Jayaraman <sjayaraman@xxxxxxx> wrote:
> Currently, the attribute cache timeout for CIFS is hardcoded to 1 second. This
> means that the client might have to issue a QPATHINFO/QFILEINFO call every 1
> second to verify if something has changes, which seems too expensive. On the
> other hand, if the timeout is hardcoded to a higher value, workloads that
> expect strict cache coherency might see unexpected results.
>
> Making attribute cache timeout as a tunable will allow us to make a tradeoff
> between performance and cache metadata correctness depending on the
> application/workload needs.
>
> Add 'actimeo' tunable that can be used to tune the attribute cache timeout.
> The default timeout is set to 1 second.
>
> Also, display actimeo option value in /proc/mounts.
>
> Cc: Jeff Layton <jlayton@xxxxxxxxxx>
> Signed-off-by: Suresh Jayaraman <sjayaraman@xxxxxxx>
> ---
> fs/cifs/cifs_fs_sb.h | 1 +
> fs/cifs/cifsfs.c | 1 +
> fs/cifs/cifsglob.h | 5 +++++
> fs/cifs/connect.c | 10 ++++++++++
> fs/cifs/inode.c | 6 +++---
> 5 files changed, 20 insertions(+), 3 deletions(-)
>
> diff --git a/fs/cifs/cifs_fs_sb.h b/fs/cifs/cifs_fs_sb.h
> index e9a393c..efd2d73 100644
> --- a/fs/cifs/cifs_fs_sb.h
> +++ b/fs/cifs/cifs_fs_sb.h
> @@ -48,6 +48,7 @@ struct cifs_sb_info {
> struct nls_table *local_nls;
> unsigned int rsize;
> unsigned int wsize;
> + unsigned int actimeo;
> atomic_t active;
> uid_t mnt_uid;
> gid_t mnt_gid;
> diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
> index 9c37897..13be23d 100644
> --- a/fs/cifs/cifsfs.c
> +++ b/fs/cifs/cifsfs.c
> @@ -461,6 +461,7 @@ cifs_show_options(struct seq_file *s, struct vfsmount *m)
>
> seq_printf(s, ",rsize=%d", cifs_sb->rsize);
> seq_printf(s, ",wsize=%d", cifs_sb->wsize);
> + seq_printf(s, ",actimeo=%d", cifs_sb->actimeo);
>
> return 0;
> }
> diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
> index b577bf0..037f793 100644
> --- a/fs/cifs/cifsglob.h
> +++ b/fs/cifs/cifsglob.h
> @@ -45,6 +45,11 @@
> #define CIFS_MIN_RCV_POOL 4
>
> /*
> + * default attribute cache timeout (seconds)
> + */
> +#define CIFS_DEF_ACTIMEO (1)
> +
> +/*
> * MAX_REQ is the maximum number of requests that WE will send
> * on one socket concurrently. It also matches the most common
> * value of max multiplex returned by servers. We may
> diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
> index 251a17c..7f92328 100644
> --- a/fs/cifs/connect.c
> +++ b/fs/cifs/connect.c
> @@ -103,6 +103,7 @@ struct smb_vol {
> bool multiuser:1;
> unsigned int rsize;
> unsigned int wsize;
> + unsigned int actimeo; /* attribute cache timeout */
> bool sockopt_tcp_nodelay:1;
> unsigned short int port;
> char *prepath;
> @@ -1214,6 +1215,10 @@ cifs_parse_mount_options(char *options, const char *devname,
> printk(KERN_WARNING "CIFS: server net"
> "biosname longer than 15 truncated.\n");
> }
> + } else if (strnicmp(data, "actimeo", 7) == 0) {
> + if (value && *value)
> + vol->actimeo =
> + simple_strtoul(value, &value, 0);
> } else if (strnicmp(data, "credentials", 4) == 0) {
> /* ignore */
> } else if (strnicmp(data, "version", 3) == 0) {
> @@ -2566,6 +2571,11 @@ static void setup_cifs_sb(struct smb_vol *pvolume_info,
> cFYI(1, "file mode: 0x%x dir mode: 0x%x",
> cifs_sb->mnt_file_mode, cifs_sb->mnt_dir_mode);
>
> + if (pvolume_info->actimeo)
> + cifs_sb->actimeo = pvolume_info->actimeo;
> + else /* default */
> + cifs_sb->actimeo = CIFS_DEF_ACTIMEO;
> +
> if (pvolume_info->noperm)
> cifs_sb->mnt_cifs_flags |= CIFS_MOUNT_NO_PERM;
> if (pvolume_info->setuids)
> diff --git a/fs/cifs/inode.c b/fs/cifs/inode.c
> index ff7d299..f30700d 100644
> --- a/fs/cifs/inode.c
> +++ b/fs/cifs/inode.c
> @@ -1648,6 +1648,7 @@ static bool
> cifs_inode_needs_reval(struct inode *inode)
> {
> struct cifsInodeInfo *cifs_i = CIFS_I(inode);
> + struct cifs_sb_info *cifs_sb = CIFS_SB(inode->i_sb);
>
> if (cifs_i->clientCanCacheRead)
> return false;
> @@ -1658,12 +1659,11 @@ cifs_inode_needs_reval(struct inode *inode)
> if (cifs_i->time == 0)
> return true;
>
> - /* FIXME: the actimeo should be tunable */
> - if (time_after_eq(jiffies, cifs_i->time + HZ))
> + if (time_after_eq(jiffies, cifs_i->time + (cifs_sb->actimeo * HZ)))
Problem:
Suppose (cifs_i->time + (cifs_sb->actimeo * HZ)) carries you
past two sign bit changes. At that point, it may look like
the resulting time is in the past, not the future.
You actually do need to impose a limit here. I suggest looking
very closely at time_before/time_after macros. It'll also be
easier to deal storing actimeo in terms of jiffies instead of
seconds.
Finally, this value needs to be displayed in /proc/mounts.
> return true;
>
> /* hardlinked files w/ noserverino get "special" treatment */
> - if (!(CIFS_SB(inode->i_sb)->mnt_cifs_flags & CIFS_MOUNT_SERVER_INUM) &&
> + if (!(cifs_sb->mnt_cifs_flags & CIFS_MOUNT_SERVER_INUM) &&
> S_ISREG(inode->i_mode) && inode->i_nlink != 1)
> return true;
>
--
Jeff Layton <jlayton@xxxxxxxxxx>
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