From: NeilBrown <neilb@suse.de> mainline inclusion from mainline-v6.10-rc1 commit 7c6c5249f061b64fc6b5b90bc147169a048691bf category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/IBCU3L Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... ---------------------------------------------------------------------- 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> Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com> Signed-off-by: Li Lingfeng <lilingfeng3@huawei.com> --- 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 d770fd24952b..78e5ff5b5a26 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, @@ -2273,6 +2275,41 @@ 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) @@ -2333,18 +2370,23 @@ 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); @@ -2356,6 +2398,12 @@ 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 4bf208a0a8e9..3f212223cd73 100644 --- a/fs/nfs/nfs3proc.c +++ b/fs/nfs/nfs3proc.c @@ -985,6 +985,7 @@ 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 e3570c656b0f..3bcc009c217b 100644 --- a/fs/nfs/proc.c +++ b/fs/nfs/proc.c @@ -694,6 +694,7 @@ 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 832b7e354b4e..aef98dd1b9e1 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 -- 2.31.1