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cifs: Fix caching to try to do open O_WRONLY as rdwr on server
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[ Upstream commit e9e6224 ]

When we're engaged in local caching of a cifs filesystem, we cannot perform
caching of a partially written cache granule unless we can read the rest of
the granule.  This can result in unexpected access errors being reported to
the user.

Fix this by the following: if a file is opened O_WRONLY locally, but the
mount was given the "-o fsc" flag, try first opening the remote file with
GENERIC_READ|GENERIC_WRITE and if that returns -EACCES, try dropping the
GENERIC_READ and doing the open again.  If that last succeeds, invalidate
the cache for that file as for O_DIRECT.

Fixes: 70431bf ("cifs: Support fscache indexing rewrite")
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Steve French <sfrench@samba.org>
cc: Shyam Prasad N <nspmangalore@gmail.com>
cc: Rohith Surabattula <rohiths.msft@gmail.com>
cc: Jeff Layton <jlayton@kernel.org>
cc: linux-cifs@vger.kernel.org
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
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@dhowells @gregkh
dhowells authored and gregkh committed Apr 10, 2024
1 parent 0f28afe commit 0fdada1
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Showing 3 changed files with 59 additions and 10 deletions.
15 changes: 15 additions & 0 deletions fs/smb/client/dir.c
View file
Expand Up @@ -189,6 +189,7 @@ static int cifs_do_create(struct inode *inode, struct dentry *direntry, unsigned
int disposition;
struct TCP_Server_Info *server = tcon->ses->server;
struct cifs_open_parms oparms;
int rdwr_for_fscache = 0;

*oplock = 0;
if (tcon->ses->server->oplocks)
Expand All @@ -200,6 +201,10 @@ static int cifs_do_create(struct inode *inode, struct dentry *direntry, unsigned
return PTR_ERR(full_path);
}

/* If we're caching, we need to be able to fill in around partial writes. */
if (cifs_fscache_enabled(inode) && (oflags & O_ACCMODE) == O_WRONLY)
rdwr_for_fscache = 1;

#ifdef CONFIG_CIFS_ALLOW_INSECURE_LEGACY
if (tcon->unix_ext && cap_unix(tcon->ses) && !tcon->broken_posix_open &&
(CIFS_UNIX_POSIX_PATH_OPS_CAP &
Expand Down Expand Up @@ -276,6 +281,8 @@ static int cifs_do_create(struct inode *inode, struct dentry *direntry, unsigned
desired_access |= GENERIC_READ; /* is this too little? */
if (OPEN_FMODE(oflags) & FMODE_WRITE)
desired_access |= GENERIC_WRITE;
if (rdwr_for_fscache == 1)
desired_access |= GENERIC_READ;

disposition = FILE_OVERWRITE_IF;
if ((oflags & (O_CREAT | O_EXCL)) == (O_CREAT | O_EXCL))
Expand Down Expand Up @@ -304,6 +311,7 @@ static int cifs_do_create(struct inode *inode, struct dentry *direntry, unsigned
if (!tcon->unix_ext && (mode & S_IWUGO) == 0)
create_options |= CREATE_OPTION_READONLY;

retry_open:
oparms = (struct cifs_open_parms) {
.tcon = tcon,
.cifs_sb = cifs_sb,
Expand All @@ -317,8 +325,15 @@ static int cifs_do_create(struct inode *inode, struct dentry *direntry, unsigned
rc = server->ops->open(xid, &oparms, oplock, buf);
if (rc) {
cifs_dbg(FYI, "cifs_create returned 0x%x\n", rc);
if (rc == -EACCES && rdwr_for_fscache == 1) {
desired_access &= ~GENERIC_READ;
rdwr_for_fscache = 2;
goto retry_open;
}
goto out;
}
if (rdwr_for_fscache == 2)
cifs_invalidate_cache(inode, FSCACHE_INVAL_DIO_WRITE);

#ifdef CONFIG_CIFS_ALLOW_INSECURE_LEGACY
/*
Expand Down
48 changes: 38 additions & 10 deletions fs/smb/client/file.c
View file
Expand Up @@ -206,12 +206,12 @@ cifs_mark_open_files_invalid(struct cifs_tcon *tcon)
*/
}

static inline int cifs_convert_flags(unsigned int flags)
static inline int cifs_convert_flags(unsigned int flags, int rdwr_for_fscache)
{
if ((flags & O_ACCMODE) == O_RDONLY)
return GENERIC_READ;
else if ((flags & O_ACCMODE) == O_WRONLY)
return GENERIC_WRITE;
return rdwr_for_fscache == 1 ? (GENERIC_READ | GENERIC_WRITE) : GENERIC_WRITE;
else if ((flags & O_ACCMODE) == O_RDWR) {
/* GENERIC_ALL is too much permission to request
can cause unnecessary access denied on create */
Expand Down Expand Up @@ -348,11 +348,16 @@ static int cifs_nt_open(const char *full_path, struct inode *inode, struct cifs_
int create_options = CREATE_NOT_DIR;
struct TCP_Server_Info *server = tcon->ses->server;
struct cifs_open_parms oparms;
int rdwr_for_fscache = 0;

if (!server->ops->open)
return -ENOSYS;

desired_access = cifs_convert_flags(f_flags);
/* If we're caching, we need to be able to fill in around partial writes. */
if (cifs_fscache_enabled(inode) && (f_flags & O_ACCMODE) == O_WRONLY)
rdwr_for_fscache = 1;

desired_access = cifs_convert_flags(f_flags, rdwr_for_fscache);

/*********************************************************************
* open flag mapping table:
Expand Down Expand Up @@ -389,6 +394,7 @@ static int cifs_nt_open(const char *full_path, struct inode *inode, struct cifs_
if (f_flags & O_DIRECT)
create_options |= CREATE_NO_BUFFER;

retry_open:
oparms = (struct cifs_open_parms) {
.tcon = tcon,
.cifs_sb = cifs_sb,
Expand All @@ -400,8 +406,16 @@ static int cifs_nt_open(const char *full_path, struct inode *inode, struct cifs_
};

rc = server->ops->open(xid, &oparms, oplock, buf);
if (rc)
if (rc) {
if (rc == -EACCES && rdwr_for_fscache == 1) {
desired_access = cifs_convert_flags(f_flags, 0);
rdwr_for_fscache = 2;
goto retry_open;
}
return rc;
}
if (rdwr_for_fscache == 2)
cifs_invalidate_cache(inode, FSCACHE_INVAL_DIO_WRITE);

/* TODO: Add support for calling posix query info but with passing in fid */
if (tcon->unix_ext)
Expand Down Expand Up @@ -834,11 +848,11 @@ int cifs_open(struct inode *inode, struct file *file)
use_cache:
fscache_use_cookie(cifs_inode_cookie(file_inode(file)),
file->f_mode & FMODE_WRITE);
if (file->f_flags & O_DIRECT &&
(!((file->f_flags & O_ACCMODE) != O_RDONLY) ||
file->f_flags & O_APPEND))
cifs_invalidate_cache(file_inode(file),
FSCACHE_INVAL_DIO_WRITE);
if (!(file->f_flags & O_DIRECT))
goto out;
if ((file->f_flags & (O_ACCMODE | O_APPEND)) == O_RDONLY)
goto out;
cifs_invalidate_cache(file_inode(file), FSCACHE_INVAL_DIO_WRITE);

out:
free_dentry_path(page);
Expand Down Expand Up @@ -903,6 +917,7 @@ cifs_reopen_file(struct cifsFileInfo *cfile, bool can_flush)
int disposition = FILE_OPEN;
int create_options = CREATE_NOT_DIR;
struct cifs_open_parms oparms;
int rdwr_for_fscache = 0;

xid = get_xid();
mutex_lock(&cfile->fh_mutex);
Expand Down Expand Up @@ -966,7 +981,11 @@ cifs_reopen_file(struct cifsFileInfo *cfile, bool can_flush)
}
#endif /* CONFIG_CIFS_ALLOW_INSECURE_LEGACY */

desired_access = cifs_convert_flags(cfile->f_flags);
/* If we're caching, we need to be able to fill in around partial writes. */
if (cifs_fscache_enabled(inode) && (cfile->f_flags & O_ACCMODE) == O_WRONLY)
rdwr_for_fscache = 1;

desired_access = cifs_convert_flags(cfile->f_flags, rdwr_for_fscache);

/* O_SYNC also has bit for O_DSYNC so following check picks up either */
if (cfile->f_flags & O_SYNC)
Expand All @@ -978,6 +997,7 @@ cifs_reopen_file(struct cifsFileInfo *cfile, bool can_flush)
if (server->ops->get_lease_key)
server->ops->get_lease_key(inode, &cfile->fid);

retry_open:
oparms = (struct cifs_open_parms) {
.tcon = tcon,
.cifs_sb = cifs_sb,
Expand All @@ -1003,6 +1023,11 @@ cifs_reopen_file(struct cifsFileInfo *cfile, bool can_flush)
/* indicate that we need to relock the file */
oparms.reconnect = true;
}
if (rc == -EACCES && rdwr_for_fscache == 1) {
desired_access = cifs_convert_flags(cfile->f_flags, 0);
rdwr_for_fscache = 2;
goto retry_open;
}

if (rc) {
mutex_unlock(&cfile->fh_mutex);
Expand All @@ -1011,6 +1036,9 @@ cifs_reopen_file(struct cifsFileInfo *cfile, bool can_flush)
goto reopen_error_exit;
}

if (rdwr_for_fscache == 2)
cifs_invalidate_cache(inode, FSCACHE_INVAL_DIO_WRITE);

#ifdef CONFIG_CIFS_ALLOW_INSECURE_LEGACY
reopen_success:
#endif /* CONFIG_CIFS_ALLOW_INSECURE_LEGACY */
Expand Down
6 changes: 6 additions & 0 deletions fs/smb/client/fscache.h
View file
Expand Up @@ -109,6 +109,11 @@ static inline void cifs_readahead_to_fscache(struct inode *inode,
__cifs_readahead_to_fscache(inode, pos, len);
}

static inline bool cifs_fscache_enabled(struct inode *inode)
{
return fscache_cookie_enabled(cifs_inode_cookie(inode));
}

#else /* CONFIG_CIFS_FSCACHE */
static inline
void cifs_fscache_fill_coherency(struct inode *inode,
Expand All @@ -124,6 +129,7 @@ static inline void cifs_fscache_release_inode_cookie(struct inode *inode) {}
static inline void cifs_fscache_unuse_inode_cookie(struct inode *inode, bool update) {}
static inline struct fscache_cookie *cifs_inode_cookie(struct inode *inode) { return NULL; }
static inline void cifs_invalidate_cache(struct inode *inode, unsigned int flags) {}
static inline bool cifs_fscache_enabled(struct inode *inode) { return false; }

static inline int cifs_fscache_query_occupancy(struct inode *inode,
pgoff_t first, unsigned int nr_pages,
Expand Down

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