On Tue, 30 Nov 2010 19:20:10 +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.
>
> It appears to me that 'actimeo' and the proposed (but not yet merged)
> 'strictcache' option cannot coexist, so care must be taken that we reset the
> other option if one of them is set.
>
> Changes since last post:
> - guard against wraparound issues with a max timeout value (25 days)
> - handle actimeo=0 condition correctly
>
> Cc: Jeff Layton <jlayton@xxxxxxxxxx>
> Signed-off-by: Suresh Jayaraman <sjayaraman@xxxxxxx>
> ---
> fs/cifs/README | 9 +++++++++
> fs/cifs/cifs_fs_sb.h | 1 +
> fs/cifs/cifsfs.c | 2 ++
> fs/cifs/cifsglob.h | 12 ++++++++++++
> fs/cifs/connect.c | 18 ++++++++++++++++++
> fs/cifs/inode.c | 7 ++++---
> 6 files changed, 46 insertions(+), 3 deletions(-)
>
> diff --git a/fs/cifs/README b/fs/cifs/README
> index ee68d10..46af99a 100644
> --- a/fs/cifs/README
> +++ b/fs/cifs/README
> @@ -337,6 +337,15 @@ A partial list of the supported mount options follows:
> wsize default write size (default 57344)
> maximum wsize currently allowed by CIFS is 57344 (fourteen
> 4096 byte pages)
> + actimeo=n attribute cache timeout in seconds (default 1 second).
> + After this timeout, the cifs client requests fresh attribute
> + information from the server. This option allows to tune the
> + attribute cache timeout to suit the workload needs. Shorter
> + timeouts mean better the cache coherency, but increased number
> + of calls to the server. Longer timeouts mean reduced number
> + of calls to the server at the expense of less stricter cache
> + coherency checks (i.e. incorrect attribute cache for a short
> + period of time).
> rw mount the network share read-write (note that the
> server may still consider the share read-only)
> ro mount network share read-only
> diff --git a/fs/cifs/cifs_fs_sb.h b/fs/cifs/cifs_fs_sb.h
> index e9a393c..7852cd6 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 long actimeo; /* attribute cache timeout (jiffies) */
> atomic_t active;
> uid_t mnt_uid;
> gid_t mnt_gid;
> diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
> index 76c8a90..56a4b75 100644
> --- a/fs/cifs/cifsfs.c
> +++ b/fs/cifs/cifsfs.c
> @@ -463,6 +463,8 @@ 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);
> + /* convert actimeo and display it in seconds */
> + seq_printf(s, ",actimeo=%lu", cifs_sb->actimeo / HZ);
>
> return 0;
> }
> diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
> index b577bf0..1c9363c 100644
> --- a/fs/cifs/cifsglob.h
> +++ b/fs/cifs/cifsglob.h
> @@ -45,6 +45,18 @@
> #define CIFS_MIN_RCV_POOL 4
>
> /*
> + * default attribute cache timeout (jiffies)
> + */
> +#define CIFS_DEF_ACTIMEO (1 * HZ)
> +
> +#define SECS_PER_DAY (24 * 60 * 60)
> +/*
> + * max attribute cache timeout (jiffies)
> + * set to 25 days which should be long enough
> + */
> +#define CIFS_MAX_ACTIMEO (SECS_PER_DAY * 25 * HZ)
> +
You're making an assumption here that HZ is not going to be bigger than
~1000. This is probably correct in most cases, but it's hard to be
certain without knowing for sure. What if someone makes an arch in a
year or so that generally uses HZ == 10000? This will still go wrong in
that case. My recommendation would be to just check that the actimeo
doesn't go over 2^30 or so after it has been converted to jiffies. That
will be simplest, I think...
> +/*
> * 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 32fa4d9..ee7cb11 100644
> --- a/fs/cifs/connect.c
> +++ b/fs/cifs/connect.c
> @@ -105,6 +105,7 @@ struct smb_vol {
> unsigned int wsize;
> bool sockopt_tcp_nodelay:1;
> unsigned short int port;
> + unsigned long actimeo; /* attribute cache timeout (jiffies) */
^^^ unused variable?
> char *prepath;
> struct sockaddr_storage srcaddr; /* allow binding to a local IP */
> struct nls_table *local_nls;
> @@ -1214,6 +1215,15 @@ 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) {
> + if (*value)
> + vol->actimeo =
> + simple_strtoul(value,
> + &value, 0) * HZ;
> + else
> + vol->actimeo = 0;
> + }
> } else if (strnicmp(data, "credentials", 4) == 0) {
> /* ignore */
> } else if (strnicmp(data, "version", 3) == 0) {
> @@ -2571,6 +2581,14 @@ 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 >= 0) {
> + if (pvolume_info->actimeo < CIFS_MAX_ACTIMEO)
> + cifs_sb->actimeo = pvolume_info->actimeo;
> + else
> + cifs_sb->actimeo = CIFS_MAX_ACTIMEO;
> + } else /* default */
> + cifs_sb->actimeo = CIFS_DEF_ACTIMEO;
> +
On NFS, actimeo=0 means to never cache attributes. Here, actime=0 will
be equivalent to the default (actimeo=1). I think it would be best to
treat actimeo=0 in a similar way to how NFS does.
Also, I wouldn't cap the actimeo to the max if someone goes over it. It
would be better to return an error instead I think.
> 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 28cb6e7..6040679 100644
> --- a/fs/cifs/inode.c
> +++ b/fs/cifs/inode.c
> @@ -1653,6 +1653,7 @@ 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;
> @@ -1663,12 +1664,12 @@ 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_in_range_open(jiffies, cifs_i->time,
> + cifs_i->time + cifs_sb->actimeo))
Good idea to use time_in_range_open for this. Might as well bound both
sides of the check.
> 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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