On 11/30/2010 07:38 PM, Jeff Layton wrote:
> 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?
We use this to store the actimeo value in jiffies as we parse the mount
options in cifs_parse_mount_options() below in this patch.
Did you mean this could be avoided?
>> 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;
>>
>
--
Suresh Jayaraman
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