| Message ID | 1362065133-9490-2-git-send-email-piastry@etersoft.ru (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Thu, Feb 28, 2013 at 7:25 AM, Pavel Shilovsky <piastry@etersoft.ru> wrote: > This patch adds 4 flags: > 1) O_DENYREAD that doesn't permit read access, > 2) O_DENYWRITE that doesn't permit write access, > 3) O_DENYDELETE that doesn't permit delete or rename, > 4) O_DENYMAND that enables O_DENY* flags checks. > > Network filesystems CIFS, SMB2.0, SMB3.0 and NFSv4 have such flags - > this change can benefit cifs and nfs modules as well as Samba and > NFS file servers. These flags are only take affect for opens with > O_DENYMAND flags - there is no impact on native Linux opens. Isn't there a problem of races here? What if another person already has the file open for WRITE and the CIFS server needs to open it with DENY WRITE? What happens if the CIFS server opens the file, but before it can issue the DENY WRITE someone else opens it for write?
2013/2/28 Richard Sharpe <realrichardsharpe@gmail.com>: > On Thu, Feb 28, 2013 at 7:25 AM, Pavel Shilovsky <piastry@etersoft.ru> wrote: >> This patch adds 4 flags: >> 1) O_DENYREAD that doesn't permit read access, >> 2) O_DENYWRITE that doesn't permit write access, >> 3) O_DENYDELETE that doesn't permit delete or rename, >> 4) O_DENYMAND that enables O_DENY* flags checks. >> >> Network filesystems CIFS, SMB2.0, SMB3.0 and NFSv4 have such flags - >> this change can benefit cifs and nfs modules as well as Samba and >> NFS file servers. These flags are only take affect for opens with >> O_DENYMAND flags - there is no impact on native Linux opens. > > Isn't there a problem of races here? What if another person already > has the file open for WRITE and the CIFS server needs to open it with > DENY WRITE? If another person already has the file open for WRITE, CIFS server can successfully open it with DENYWRITE, because this DENY* behavior affects only DENYMAND opens. > > What happens if the CIFS server opens the file, but before it can > issue the DENY WRITE someone else opens it for write? The same things - CIFS server will open and lock the file without problems.
diff --git a/fs/fcntl.c b/fs/fcntl.c index 71a600a..d88a548 100644 --- a/fs/fcntl.c +++ b/fs/fcntl.c @@ -730,14 +730,15 @@ static int __init fcntl_init(void) * Exceptions: O_NONBLOCK is a two bit define on parisc; O_NDELAY * is defined as O_NONBLOCK on some platforms and not on others. */ - BUILD_BUG_ON(19 - 1 /* for O_RDONLY being 0 */ != HWEIGHT32( + BUILD_BUG_ON(23 - 1 /* for O_RDONLY being 0 */ != HWEIGHT32( O_RDONLY | O_WRONLY | O_RDWR | O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC | O_APPEND | /* O_NONBLOCK | */ __O_SYNC | O_DSYNC | FASYNC | O_DIRECT | O_LARGEFILE | O_DIRECTORY | O_NOFOLLOW | O_NOATIME | O_CLOEXEC | - __FMODE_EXEC | O_PATH + __FMODE_EXEC | O_PATH | O_DENYREAD | + O_DENYWRITE | O_DENYDELETE | O_DENYMAND )); fasync_cache = kmem_cache_create("fasync_cache", diff --git a/include/uapi/asm-generic/fcntl.h b/include/uapi/asm-generic/fcntl.h index a48937d..6e4e979 100644 --- a/include/uapi/asm-generic/fcntl.h +++ b/include/uapi/asm-generic/fcntl.h @@ -84,6 +84,20 @@ #define O_PATH 010000000 #endif +#ifndef O_DENYREAD +#define O_DENYREAD 020000000 /* Do not permit read access */ +#endif +#ifndef O_DENYWRITE +#define O_DENYWRITE 040000000 /* Do not permit write access */ +#endif +/* FMODE_NONOTIFY 0100000000 */ +#ifndef O_DENYDELETE +#define O_DENYDELETE 0200000000 /* Do not permit delete or rename */ +#endif +#ifndef O_DENYMAND +#define O_DENYMAND 0400000000 /* Enable O_DENY flags checks */ +#endif + #ifndef O_NDELAY #define O_NDELAY O_NONBLOCK #endif
This patch adds 4 flags: 1) O_DENYREAD that doesn't permit read access, 2) O_DENYWRITE that doesn't permit write access, 3) O_DENYDELETE that doesn't permit delete or rename, 4) O_DENYMAND that enables O_DENY* flags checks. Network filesystems CIFS, SMB2.0, SMB3.0 and NFSv4 have such flags - this change can benefit cifs and nfs modules as well as Samba and NFS file servers. These flags are only take affect for opens with O_DENYMAND flags - there is no impact on native Linux opens. Signed-off-by: Pavel Shilovsky <piastry@etersoft.ru> --- fs/fcntl.c | 5 +++-- include/uapi/asm-generic/fcntl.h | 14 ++++++++++++++ 2 files changed, 17 insertions(+), 2 deletions(-)