| Message ID | 171134496555.13576.1334297096866165638@noble.neil.brown.name (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | NFS: add atomic_open for NFSv3 to handle O_TRUNC correctly. | expand |
Hi, any thoughts about this patch and/or the problem it addresses? Thanks, NeilBrown On Mon, 25 Mar 2024, NeilBrown wrote: > With two clients, each with NFSv3 mounts of the same directory, the sequence: > > client1 client2 > ls -l afile > echo hello there > afile > echo HELLO > afile > cat afile > > will show > HELLO > there > > because the O_TRUNC requested in the final 'echo' doesn't take effect. > This is because the "Negative dentry, just create a file" section in > lookup_open() assumes that the file *does* get created since the dentry > was negative, so it sets FMODE_CREATED, and this causes do_open() to > clear O_TRUNC and so the file doesn't get truncated. > > Even mounting with -o lookupcache=none does not help as > nfs_neg_need_reval() always returns false if LOOKUP_CREATE is set. > > This patch fixes the problem by providing an atomic_open inode operation > for NFSv3 (and v2). The code is largely the code from the branch in > lookup_open() when atomic_open is not provided. The significant change > is that the O_TRUNC flag is passed a new nfs_do_create() which add > 'trunc' handling to nfs_create(). > > With this change we also optimise away an unnecessary LOOKUP before the > file is created. > > Signed-off-by: NeilBrown <neilb@suse.de> > --- > fs/nfs/dir.c | 54 +++++++++++++++++++++++++++++++++++++++--- > fs/nfs/nfs3proc.c | 1 + > fs/nfs/proc.c | 1 + > include/linux/nfs_fs.h | 3 +++ > 4 files changed, 56 insertions(+), 3 deletions(-) > > diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c > index ac505671efbd..342930996226 100644 > --- a/fs/nfs/dir.c > +++ b/fs/nfs/dir.c > @@ -56,6 +56,8 @@ static int nfs_readdir(struct file *, struct dir_context *); > static int nfs_fsync_dir(struct file *, loff_t, loff_t, int); > static loff_t nfs_llseek_dir(struct file *, loff_t, int); > static void nfs_readdir_clear_array(struct folio *); > +static int nfs_do_create(struct inode *dir, struct dentry *dentry, > + umode_t mode, int open_flags); > > const struct file_operations nfs_dir_operations = { > .llseek = nfs_llseek_dir, > @@ -2243,6 +2245,41 @@ static int nfs4_lookup_revalidate(struct dentry *dentry, unsigned int flags) > > #endif /* CONFIG_NFSV4 */ > > +int nfs_atomic_open_v23(struct inode *dir, struct dentry *dentry, > + struct file *file, unsigned int open_flags, > + umode_t mode) > +{ > + > + /* Same as look+open from lookup_open(), but with different O_TRUNC > + * handling. > + */ > + int error = 0; > + > + if (open_flags & O_CREAT) { > + file->f_mode |= FMODE_CREATED; > + error = nfs_do_create(dir, dentry, mode, open_flags); > + if (error) > + return error; > + return finish_open(file, dentry, NULL); > + } else if (d_in_lookup(dentry)) { > + /* The only flags nfs_lookup considers are > + * LOOKUP_EXCL and LOOKUP_RENAME_TARGET, and > + * we want those to be zero so the lookup isn't skipped. > + */ > + struct dentry *res = nfs_lookup(dir, dentry, 0); > + > + d_lookup_done(dentry); > + if (unlikely(res)) { > + if (IS_ERR(res)) > + return PTR_ERR(res); > + return finish_no_open(file, res); > + } > + } > + return finish_no_open(file, NULL); > + > +} > +EXPORT_SYMBOL_GPL(nfs_atomic_open_v23); > + > struct dentry * > nfs_add_or_obtain(struct dentry *dentry, struct nfs_fh *fhandle, > struct nfs_fattr *fattr) > @@ -2303,18 +2340,23 @@ EXPORT_SYMBOL_GPL(nfs_instantiate); > * that the operation succeeded on the server, but an error in the > * reply path made it appear to have failed. > */ > -int nfs_create(struct mnt_idmap *idmap, struct inode *dir, > - struct dentry *dentry, umode_t mode, bool excl) > +static int nfs_do_create(struct inode *dir, struct dentry *dentry, > + umode_t mode, int open_flags) > { > struct iattr attr; > - int open_flags = excl ? O_CREAT | O_EXCL : O_CREAT; > int error; > > + open_flags |= O_CREAT; > + > dfprintk(VFS, "NFS: create(%s/%lu), %pd\n", > dir->i_sb->s_id, dir->i_ino, dentry); > > attr.ia_mode = mode; > attr.ia_valid = ATTR_MODE; > + if (open_flags & O_TRUNC) { > + attr.ia_size = 0; > + attr.ia_valid |= ATTR_SIZE; > + } > > trace_nfs_create_enter(dir, dentry, open_flags); > error = NFS_PROTO(dir)->create(dir, dentry, &attr, open_flags); > @@ -2326,6 +2368,12 @@ int nfs_create(struct mnt_idmap *idmap, struct inode *dir, > d_drop(dentry); > return error; > } > + > +int nfs_create(struct mnt_idmap *idmap, struct inode *dir, > + struct dentry *dentry, umode_t mode, bool excl) > +{ > + return nfs_do_create(dir, dentry, mode, excl ? O_EXCL : 0); > +} > EXPORT_SYMBOL_GPL(nfs_create); > > /* > diff --git a/fs/nfs/nfs3proc.c b/fs/nfs/nfs3proc.c > index cbbe3f0193b8..74bda639a7cf 100644 > --- a/fs/nfs/nfs3proc.c > +++ b/fs/nfs/nfs3proc.c > @@ -986,6 +986,7 @@ static int nfs3_have_delegation(struct inode *inode, fmode_t flags) > > static const struct inode_operations nfs3_dir_inode_operations = { > .create = nfs_create, > + .atomic_open = nfs_atomic_open_v23, > .lookup = nfs_lookup, > .link = nfs_link, > .unlink = nfs_unlink, > diff --git a/fs/nfs/proc.c b/fs/nfs/proc.c > index ad3a321ae997..d105e5b2659d 100644 > --- a/fs/nfs/proc.c > +++ b/fs/nfs/proc.c > @@ -695,6 +695,7 @@ static int nfs_have_delegation(struct inode *inode, fmode_t flags) > static const struct inode_operations nfs_dir_inode_operations = { > .create = nfs_create, > .lookup = nfs_lookup, > + .atomic_open = nfs_atomic_open_v23, > .link = nfs_link, > .unlink = nfs_unlink, > .symlink = nfs_symlink, > diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h > index d59116ac8209..039898d70954 100644 > --- a/include/linux/nfs_fs.h > +++ b/include/linux/nfs_fs.h > @@ -561,6 +561,9 @@ extern int nfs_may_open(struct inode *inode, const struct cred *cred, int openfl > extern void nfs_access_zap_cache(struct inode *inode); > extern int nfs_access_get_cached(struct inode *inode, const struct cred *cred, > u32 *mask, bool may_block); > +extern int nfs_atomic_open_v23(struct inode *dir, struct dentry *dentry, > + struct file *file, unsigned int open_flags, > + umode_t mode); > > /* > * linux/fs/nfs/symlink.c > -- > 2.44.0 > > >
diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c index ac505671efbd..342930996226 100644 --- a/fs/nfs/dir.c +++ b/fs/nfs/dir.c @@ -56,6 +56,8 @@ static int nfs_readdir(struct file *, struct dir_context *); static int nfs_fsync_dir(struct file *, loff_t, loff_t, int); static loff_t nfs_llseek_dir(struct file *, loff_t, int); static void nfs_readdir_clear_array(struct folio *); +static int nfs_do_create(struct inode *dir, struct dentry *dentry, + umode_t mode, int open_flags); const struct file_operations nfs_dir_operations = { .llseek = nfs_llseek_dir, @@ -2243,6 +2245,41 @@ static int nfs4_lookup_revalidate(struct dentry *dentry, unsigned int flags) #endif /* CONFIG_NFSV4 */ +int nfs_atomic_open_v23(struct inode *dir, struct dentry *dentry, + struct file *file, unsigned int open_flags, + umode_t mode) +{ + + /* Same as look+open from lookup_open(), but with different O_TRUNC + * handling. + */ + int error = 0; + + if (open_flags & O_CREAT) { + file->f_mode |= FMODE_CREATED; + error = nfs_do_create(dir, dentry, mode, open_flags); + if (error) + return error; + return finish_open(file, dentry, NULL); + } else if (d_in_lookup(dentry)) { + /* The only flags nfs_lookup considers are + * LOOKUP_EXCL and LOOKUP_RENAME_TARGET, and + * we want those to be zero so the lookup isn't skipped. + */ + struct dentry *res = nfs_lookup(dir, dentry, 0); + + d_lookup_done(dentry); + if (unlikely(res)) { + if (IS_ERR(res)) + return PTR_ERR(res); + return finish_no_open(file, res); + } + } + return finish_no_open(file, NULL); + +} +EXPORT_SYMBOL_GPL(nfs_atomic_open_v23); + struct dentry * nfs_add_or_obtain(struct dentry *dentry, struct nfs_fh *fhandle, struct nfs_fattr *fattr) @@ -2303,18 +2340,23 @@ EXPORT_SYMBOL_GPL(nfs_instantiate); * that the operation succeeded on the server, but an error in the * reply path made it appear to have failed. */ -int nfs_create(struct mnt_idmap *idmap, struct inode *dir, - struct dentry *dentry, umode_t mode, bool excl) +static int nfs_do_create(struct inode *dir, struct dentry *dentry, + umode_t mode, int open_flags) { struct iattr attr; - int open_flags = excl ? O_CREAT | O_EXCL : O_CREAT; int error; + open_flags |= O_CREAT; + dfprintk(VFS, "NFS: create(%s/%lu), %pd\n", dir->i_sb->s_id, dir->i_ino, dentry); attr.ia_mode = mode; attr.ia_valid = ATTR_MODE; + if (open_flags & O_TRUNC) { + attr.ia_size = 0; + attr.ia_valid |= ATTR_SIZE; + } trace_nfs_create_enter(dir, dentry, open_flags); error = NFS_PROTO(dir)->create(dir, dentry, &attr, open_flags); @@ -2326,6 +2368,12 @@ int nfs_create(struct mnt_idmap *idmap, struct inode *dir, d_drop(dentry); return error; } + +int nfs_create(struct mnt_idmap *idmap, struct inode *dir, + struct dentry *dentry, umode_t mode, bool excl) +{ + return nfs_do_create(dir, dentry, mode, excl ? O_EXCL : 0); +} EXPORT_SYMBOL_GPL(nfs_create); /* diff --git a/fs/nfs/nfs3proc.c b/fs/nfs/nfs3proc.c index cbbe3f0193b8..74bda639a7cf 100644 --- a/fs/nfs/nfs3proc.c +++ b/fs/nfs/nfs3proc.c @@ -986,6 +986,7 @@ static int nfs3_have_delegation(struct inode *inode, fmode_t flags) static const struct inode_operations nfs3_dir_inode_operations = { .create = nfs_create, + .atomic_open = nfs_atomic_open_v23, .lookup = nfs_lookup, .link = nfs_link, .unlink = nfs_unlink, diff --git a/fs/nfs/proc.c b/fs/nfs/proc.c index ad3a321ae997..d105e5b2659d 100644 --- a/fs/nfs/proc.c +++ b/fs/nfs/proc.c @@ -695,6 +695,7 @@ static int nfs_have_delegation(struct inode *inode, fmode_t flags) static const struct inode_operations nfs_dir_inode_operations = { .create = nfs_create, .lookup = nfs_lookup, + .atomic_open = nfs_atomic_open_v23, .link = nfs_link, .unlink = nfs_unlink, .symlink = nfs_symlink, diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h index d59116ac8209..039898d70954 100644 --- a/include/linux/nfs_fs.h +++ b/include/linux/nfs_fs.h @@ -561,6 +561,9 @@ extern int nfs_may_open(struct inode *inode, const struct cred *cred, int openfl extern void nfs_access_zap_cache(struct inode *inode); extern int nfs_access_get_cached(struct inode *inode, const struct cred *cred, u32 *mask, bool may_block); +extern int nfs_atomic_open_v23(struct inode *dir, struct dentry *dentry, + struct file *file, unsigned int open_flags, + umode_t mode); /* * linux/fs/nfs/symlink.c
With two clients, each with NFSv3 mounts of the same directory, the sequence: client1 client2 ls -l afile echo hello there > afile echo HELLO > afile cat afile will show HELLO there because the O_TRUNC requested in the final 'echo' doesn't take effect. This is because the "Negative dentry, just create a file" section in lookup_open() assumes that the file *does* get created since the dentry was negative, so it sets FMODE_CREATED, and this causes do_open() to clear O_TRUNC and so the file doesn't get truncated. Even mounting with -o lookupcache=none does not help as nfs_neg_need_reval() always returns false if LOOKUP_CREATE is set. This patch fixes the problem by providing an atomic_open inode operation for NFSv3 (and v2). The code is largely the code from the branch in lookup_open() when atomic_open is not provided. The significant change is that the O_TRUNC flag is passed a new nfs_do_create() which add 'trunc' handling to nfs_create(). With this change we also optimise away an unnecessary LOOKUP before the file is created. Signed-off-by: NeilBrown <neilb@suse.de> --- fs/nfs/dir.c | 54 +++++++++++++++++++++++++++++++++++++++--- fs/nfs/nfs3proc.c | 1 + fs/nfs/proc.c | 1 + include/linux/nfs_fs.h | 3 +++ 4 files changed, 56 insertions(+), 3 deletions(-)