linux/fs/nfsd/filecache.h
Jeff Layton 0b3a551fa5 nfsd: fix handling of cached open files in nfsd4_open codepath
Commit fb70bf124b ("NFSD: Instantiate a struct file when creating a
regular NFSv4 file") added the ability to cache an open fd over a
compound. There are a couple of problems with the way this currently
works:

It's racy, as a newly-created nfsd_file can end up with its PENDING bit
cleared while the nf is hashed, and the nf_file pointer is still zeroed
out. Other tasks can find it in this state and they expect to see a
valid nf_file, and can oops if nf_file is NULL.

Also, there is no guarantee that we'll end up creating a new nfsd_file
if one is already in the hash. If an extant entry is in the hash with a
valid nf_file, nfs4_get_vfs_file will clobber its nf_file pointer with
the value of op_file and the old nf_file will leak.

Fix both issues by making a new nfsd_file_acquirei_opened variant that
takes an optional file pointer. If one is present when this is called,
we'll take a new reference to it instead of trying to open the file. If
the nfsd_file already has a valid nf_file, we'll just ignore the
optional file and pass the nfsd_file back as-is.

Also rework the tracepoints a bit to allow for an "opened" variant and
don't try to avoid counting acquisitions in the case where we already
have a cached open file.

Fixes: fb70bf124b ("NFSD: Instantiate a struct file when creating a regular NFSv4 file")
Cc: Trond Myklebust <trondmy@hammerspace.com>
Reported-by: Stanislav Saner <ssaner@redhat.com>
Reported-and-Tested-by: Ruben Vestergaard <rubenv@drcmr.dk>
Reported-and-Tested-by: Torkil Svensgaard <torkil@drcmr.dk>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
2023-01-06 13:17:06 -05:00

68 lines
2.6 KiB
C

#ifndef _FS_NFSD_FILECACHE_H
#define _FS_NFSD_FILECACHE_H
#include <linux/fsnotify_backend.h>
/*
* This is the fsnotify_mark container that nfsd attaches to the files that it
* is holding open. Note that we have a separate refcount here aside from the
* one in the fsnotify_mark. We only want a single fsnotify_mark attached to
* the inode, and for each nfsd_file to hold a reference to it.
*
* The fsnotify_mark is itself refcounted, but that's not sufficient to tell us
* how to put that reference. If there are still outstanding nfsd_files that
* reference the mark, then we would want to call fsnotify_put_mark on it.
* If there were not, then we'd need to call fsnotify_destroy_mark. Since we
* can't really tell the difference, we use the nfm_mark to keep track of how
* many nfsd_files hold references to the mark. When that counter goes to zero
* then we know to call fsnotify_destroy_mark on it.
*/
struct nfsd_file_mark {
struct fsnotify_mark nfm_mark;
refcount_t nfm_ref;
};
/*
* A representation of a file that has been opened by knfsd. These are hashed
* in the hashtable by inode pointer value. Note that this object doesn't
* hold a reference to the inode by itself, so the nf_inode pointer should
* never be dereferenced, only used for comparison.
*/
struct nfsd_file {
struct rhash_head nf_rhash;
struct list_head nf_lru;
struct rcu_head nf_rcu;
struct file *nf_file;
const struct cred *nf_cred;
struct net *nf_net;
#define NFSD_FILE_HASHED (0)
#define NFSD_FILE_PENDING (1)
#define NFSD_FILE_REFERENCED (2)
#define NFSD_FILE_GC (3)
unsigned long nf_flags;
struct inode *nf_inode; /* don't deref */
refcount_t nf_ref;
unsigned char nf_may;
struct nfsd_file_mark *nf_mark;
ktime_t nf_birthtime;
};
int nfsd_file_cache_init(void);
void nfsd_file_cache_purge(struct net *);
void nfsd_file_cache_shutdown(void);
int nfsd_file_cache_start_net(struct net *net);
void nfsd_file_cache_shutdown_net(struct net *net);
void nfsd_file_put(struct nfsd_file *nf);
struct nfsd_file *nfsd_file_get(struct nfsd_file *nf);
void nfsd_file_close_inode_sync(struct inode *inode);
bool nfsd_file_is_cached(struct inode *inode);
__be32 nfsd_file_acquire_gc(struct svc_rqst *rqstp, struct svc_fh *fhp,
unsigned int may_flags, struct nfsd_file **nfp);
__be32 nfsd_file_acquire(struct svc_rqst *rqstp, struct svc_fh *fhp,
unsigned int may_flags, struct nfsd_file **nfp);
__be32 nfsd_file_acquire_opened(struct svc_rqst *rqstp, struct svc_fh *fhp,
unsigned int may_flags, struct file *file,
struct nfsd_file **nfp);
int nfsd_file_cache_stats_show(struct seq_file *m, void *v);
#endif /* _FS_NFSD_FILECACHE_H */