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NFS: Fix the resolution problem with nfs_inode_attrs_need_update()

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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
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14
fs/nfs/dir.c
View File

@ -156,6 +156,7 @@ typedef struct {
decode_dirent_t decode;
int plus;
unsigned long timestamp;
unsigned long gencount;
int timestamp_valid;
} nfs_readdir_descriptor_t;
@ -177,7 +178,7 @@ int nfs_readdir_filler(nfs_readdir_descriptor_t *desc, struct page *page)
struct file *file = desc->file;
struct inode *inode = file->f_path.dentry->d_inode;
struct rpc_cred *cred = nfs_file_cred(file);
unsigned long timestamp;
unsigned long timestamp, gencount;
int error;
dfprintk(DIRCACHE, "NFS: %s: reading cookie %Lu into page %lu\n",
@ -186,6 +187,7 @@ int nfs_readdir_filler(nfs_readdir_descriptor_t *desc, struct page *page)
again:
timestamp = jiffies;
gencount = nfs_inc_attr_generation_counter();
error = NFS_PROTO(inode)->readdir(file->f_path.dentry, cred, desc->entry->cookie, page,
NFS_SERVER(inode)->dtsize, desc->plus);
if (error < 0) {
@ -199,6 +201,7 @@ int nfs_readdir_filler(nfs_readdir_descriptor_t *desc, struct page *page)
goto error;
}
desc->timestamp = timestamp;
desc->gencount = gencount;
desc->timestamp_valid = 1;
SetPageUptodate(page);
/* Ensure consistent page alignment of the data.
@ -224,9 +227,10 @@ int dir_decode(nfs_readdir_descriptor_t *desc)
if (IS_ERR(p))
return PTR_ERR(p);
desc->ptr = p;
if (desc->timestamp_valid)
if (desc->timestamp_valid) {
desc->entry->fattr->time_start = desc->timestamp;
else
desc->entry->fattr->gencount = desc->gencount;
} else
desc->entry->fattr->valid &= ~NFS_ATTR_FATTR;
return 0;
}
@ -471,7 +475,7 @@ int uncached_readdir(nfs_readdir_descriptor_t *desc, void *dirent,
struct rpc_cred *cred = nfs_file_cred(file);
struct page *page = NULL;
int status;
unsigned long timestamp;
unsigned long timestamp, gencount;
dfprintk(DIRCACHE, "NFS: uncached_readdir() searching for cookie %Lu\n",
(unsigned long long)*desc->dir_cookie);
@ -482,6 +486,7 @@ int uncached_readdir(nfs_readdir_descriptor_t *desc, void *dirent,
goto out;
}
timestamp = jiffies;
gencount = nfs_inc_attr_generation_counter();
status = NFS_PROTO(inode)->readdir(file->f_path.dentry, cred,
*desc->dir_cookie, page,
NFS_SERVER(inode)->dtsize,
@ -490,6 +495,7 @@ int uncached_readdir(nfs_readdir_descriptor_t *desc, void *dirent,
desc->ptr = kmap(page); /* matching kunmap in nfs_do_filldir */
if (status >= 0) {
desc->timestamp = timestamp;
desc->gencount = gencount;
desc->timestamp_valid = 1;
if ((status = dir_decode(desc)) == 0)
desc->entry->prev_cookie = *desc->dir_cookie;

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))

10
include/linux/nfs_fs.h
View File

@ -137,7 +137,7 @@ struct nfs_inode {
unsigned long attrtimeo_timestamp;
__u64 change_attr; /* v4 only */
unsigned long last_updated;
unsigned long attr_gencount;
/* "Generation counter" for the attribute cache. This is
* bumped whenever we update the metadata on the
* server.
@ -344,15 +344,11 @@ extern struct nfs_open_context *get_nfs_open_context(struct nfs_open_context *ct
extern void put_nfs_open_context(struct nfs_open_context *ctx);
extern struct nfs_open_context *nfs_find_open_context(struct inode *inode, struct rpc_cred *cred, int mode);
extern u64 nfs_compat_user_ino64(u64 fileid);
extern void nfs_fattr_init(struct nfs_fattr *fattr);
/* linux/net/ipv4/ipconfig.c: trims ip addr off front of name, too. */
extern __be32 root_nfs_parse_addr(char *name); /*__init*/
static inline void nfs_fattr_init(struct nfs_fattr *fattr)
{
fattr->valid = 0;
fattr->time_start = jiffies;
}
extern unsigned long nfs_inc_attr_generation_counter(void);
/*
* linux/fs/nfs/file.c

1
include/linux/nfs_xdr.h
View File

@ -56,6 +56,7 @@ struct nfs_fattr {
__u64 change_attr; /* NFSv4 change attribute */
__u64 pre_change_attr;/* pre-op NFSv4 change attribute */
unsigned long time_start;
unsigned long gencount;
};
#define NFS_ATTR_WCC 0x0001 /* pre-op WCC data */