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bh=u1MNFR1J8Qr84QGzW7VULoXALPQtETjnepSLKirSNE8=; b=nQbihhzH2uyTqwG0sLMhN94Fnpmbw4zWx2B2KV50UgyvDSCqiVBN73EcUvd+4xyxYiL3Q+ z9tS2XWKQdr9+dDQ== Received: from imap1.dmz-prg2.suse.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by imap1.dmz-prg2.suse.org (Postfix) with ESMTPS id 5C3C113A7B; Tue, 5 Mar 2024 02:10:23 +0000 (UTC) Received: from dovecot-director2.suse.de ([10.150.64.162]) by imap1.dmz-prg2.suse.org with ESMTPSA id Gm2JAA9/5mUTFgAAD6G6ig (envelope-from ); Tue, 05 Mar 2024 02:10:23 +0000 Precedence: bulk X-Mailing-List: linux-nfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 From: "NeilBrown" To: Trond Myklebust , Anna Schumaker Cc: linux-nfs@vger.kernel.org Subject: [PATCH/RFC] NFS: add atomic_open for NFSv3 to handle O_TRUNC correctly. Date: Tue, 05 Mar 2024 13:10:19 +1100 Message-id: <170960461960.24797.16435704587383279525@noble.neil.brown.name> Authentication-Results: smtp-out1.suse.de; dkim=pass header.d=suse.de header.s=susede2_rsa header.b=R1Z4txzX; dkim=pass header.d=suse.de header.s=susede2_ed25519 header.b=nQbihhzH X-Spamd-Result: default: False [-3.31 / 50.00]; ARC_NA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; R_DKIM_ALLOW(-0.20)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; SPAMHAUS_XBL(0.00)[2a07:de40:b281:104:10:150:64:97:from]; FROM_HAS_DN(0.00)[]; RCPT_COUNT_THREE(0.00)[3]; TO_DN_SOME(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; MIME_GOOD(-0.10)[text/plain]; RCVD_COUNT_THREE(0.00)[3]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; DKIM_TRACE(0.00)[suse.de:+]; MX_GOOD(-0.01)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:dkim,suse.de:email]; FUZZY_BLOCKED(0.00)[rspamd.com]; FROM_EQ_ENVFROM(0.00)[]; MIME_TRACE(0.00)[0:+]; RCVD_TLS_ALL(0.00)[]; BAYES_HAM(-3.00)[100.00%] X-Rspamd-Server: rspamd1.dmz-prg2.suse.org X-Rspamd-Queue-Id: D69EF229A4 X-Spam-Level: X-Spam-Score: -3.31 X-Spam-Flag: NO With two clients 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(). Signed-off-by: NeilBrown --- This is the first time I seriously looked at the atomic_lookup interface so I might have done something silly. Please expect to find something wrong :-) I've only done basic testing so far. I plan to run some test suites tomorrow, but thought I would post now to get initial feedback. Thanks. fs/nfs/dir.c | 55 ++++++++++++++++++++++++++++++++++++++++-- fs/nfs/nfs3proc.c | 1 + fs/nfs/proc.c | 1 + include/linux/nfs_fs.h | 3 +++ 4 files changed, 58 insertions(+), 2 deletions(-) diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c index ac505671efbd..48a3a3455f00 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 mnt_idmap *idmap, struct inode *dir, + struct dentry *dentry, umode_t mode, bool excl, bool trunc); const struct file_operations nfs_dir_operations = { .llseek = nfs_llseek_dir, @@ -2243,6 +2245,45 @@ 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 we different O_TRUNC + * handling. + */ + int error = 0; + unsigned int lookup_flags = 0; + + if (open_flags & O_DIRECTORY) + lookup_flags = LOOKUP_OPEN | LOOKUP_DIRECTORY; + if (open_flags & O_EXCL) + lookup_flags |= LOOKUP_EXCL; + + if (d_in_lookup(dentry)) { + struct dentry *res = nfs_lookup(dir, dentry, open_flags); + + d_lookup_done(dentry); + if (unlikely(res)) { + if (IS_ERR(res)) + return PTR_ERR(res); + return finish_no_open(file, res); + } + } + + /* Negative dentry, just create the file */ + if (!dentry->d_inode && (open_flags & O_CREAT)) { + file->f_mode |= FMODE_CREATED; + error = nfs_do_create(NULL, dir, dentry, mode, + open_flags & O_EXCL, open_flags & O_TRUNC); + if (error) + return error; + } + return finish_open(file, dentry, 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) @@ -2303,8 +2344,8 @@ 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 mnt_idmap *idmap, struct inode *dir, + struct dentry *dentry, umode_t mode, bool excl, bool trunc) { struct iattr attr; int open_flags = excl ? O_CREAT | O_EXCL : O_CREAT; @@ -2315,6 +2356,10 @@ int nfs_create(struct mnt_idmap *idmap, struct inode *dir, attr.ia_mode = mode; attr.ia_valid = ATTR_MODE; + if (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 +2371,12 @@ 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(idmap, dir, dentry, mode, excl, false); +} EXPORT_SYMBOL_GPL(nfs_create); /* diff --git a/fs/nfs/nfs3proc.c b/fs/nfs/nfs3proc.c index 2de66e4e8280..15ddf6755ede 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 f5ce7b101146..cacbeb397a58 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