lk/linux-kernel-test
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

NFS: Fix the resolution problem with nfs_inode_attrs_need_update()

Browse Source 
It appears that 'jiffies' timestamps do not have high enough resolution for
nfs_inode_attrs_need_update(). One problem is that a GETATTR can be
launched within < 1 jiffy of the last operation that updated the attribute.
Another problem is that RPC calls can take < 1 jiffy to execute.

We can fix this by switching the variables to use a simple global counter
that gets incremented every time we start another GETATTR call.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
This commit is contained in:
Trond Myklebust
2008-10-14 19:16:07 -04:00
parent 921615f111
commit 4704f0e274
4 changed files with 44 additions and 18 deletions
Download Patch File Download Diff File Expand all files Collapse all files

37
fs/nfs/inode.c
View File

@ -305,7 +305,7 @@ nfs_fhget(struct super_block *sb, struct nfs_fh *fh, struct nfs_fattr *fattr)
init_special_inode(inode, inode->i_mode, fattr->rdev);
nfsi->read_cache_jiffies = fattr->time_start;
nfsi->last_updated = now;
nfsi->attr_gencount = fattr->gencount;
nfsi->cache_change_attribute = now;
inode->i_atime = fattr->atime;
inode->i_mtime = fattr->mtime;
@ -909,6 +909,30 @@ static int nfs_size_need_update(const struct inode *inode, const struct nfs_fatt
return nfs_size_to_loff_t(fattr->size) > i_size_read(inode);
}
static unsigned long nfs_attr_generation_counter;
static unsigned long nfs_read_attr_generation_counter(void)
{
smp_rmb();
return nfs_attr_generation_counter;
}
unsigned long nfs_inc_attr_generation_counter(void)
{
unsigned long ret;
smp_rmb();
ret = ++nfs_attr_generation_counter;
smp_wmb();
return ret;
}
void nfs_fattr_init(struct nfs_fattr *fattr)
{
fattr->valid = 0;
fattr->time_start = jiffies;
fattr->gencount = nfs_inc_attr_generation_counter();
}
/**
* nfs_inode_attrs_need_update - check if the inode attributes need updating
* @inode - pointer to inode
@ -922,8 +946,7 @@ static int nfs_size_need_update(const struct inode *inode, const struct nfs_fatt
* catch the case where ctime either didn't change, or went backwards
* (if someone reset the clock on the server) by looking at whether
* or not this RPC call was started after the inode was last updated.
* Note also the check for jiffy wraparound if the last_updated timestamp
* is later than 'jiffies'.
* Note also the check for wraparound of 'attr_gencount'
*
* The function returns 'true' if it thinks the attributes in 'fattr' are
* more recent than the ones cached in the inode.
@ -933,10 +956,10 @@ static int nfs_inode_attrs_need_update(const struct inode *inode, const struct n
{
const struct nfs_inode *nfsi = NFS_I(inode);
return time_after(fattr->time_start, nfsi->last_updated) ||
return ((long)fattr->gencount - (long)nfsi->attr_gencount) > 0 ||
nfs_ctime_need_update(inode, fattr) ||
nfs_size_need_update(inode, fattr) ||
time_after(nfsi->last_updated, jiffies);
((long)nfsi->attr_gencount - (long)nfs_read_attr_generation_counter() > 0);
}
static int nfs_refresh_inode_locked(struct inode *inode, struct nfs_fattr *fattr)
@ -1107,7 +1130,7 @@ static int nfs_update_inode(struct inode *inode, struct nfs_fattr *fattr)
}
/* If ctime has changed we should definitely clear access+acl caches */
if (!timespec_equal(&inode->i_ctime, &fattr->ctime))
invalid |= NFS_INO_INVALID_ACCESS|NFS_INO_INVALID_ACL;
invalid |= NFS_INO_INVALID_ATTR|NFS_INO_INVALID_ACCESS|NFS_INO_INVALID_ACL;
} else if (nfsi->change_attr != fattr->change_attr) {
dprintk("NFS: change_attr change on server for file %s/%ld\n",
inode->i_sb->s_id, inode->i_ino);
@ -1163,7 +1186,7 @@ static int nfs_update_inode(struct inode *inode, struct nfs_fattr *fattr)
nfs_inc_stats(inode, NFSIOS_ATTRINVALIDATE);
nfsi->attrtimeo = NFS_MINATTRTIMEO(inode);
nfsi->attrtimeo_timestamp = now;
nfsi->last_updated = now;
nfsi->attr_gencount = nfs_inc_attr_generation_counter();
} else {
if (!time_in_range(now, nfsi->attrtimeo_timestamp, nfsi->attrtimeo_timestamp + nfsi->attrtimeo)) {
if ((nfsi->attrtimeo <<= 1) > NFS_MAXATTRTIMEO(inode))