Message ID | 1324134422-16642-1-git-send-email-levinsasha928@gmail.com |
---|---|
State | Not Applicable, archived |
Delegated to: | David Miller |
Headers | show |
On Sat, Dec 17, 2011 at 05:07:02PM +0200, Sasha Levin wrote: > struct p9_iattr_dotl is userspace facing, but the 'valid' field is documented > as follows: > > * @valid: bitfield specifying which fields are valid > * same as in struct iattr > > Which means that the user has to know about kernel internal ATTR_* values. > > On Fri, 2011-12-16 at 23:30 +0000, Al Viro wrote: > > They *are* kernel internal values and 9P is asking for trouble exposing > > them. Translation: tomorrow we might reassign those as we bloody wish > > and any userland code that happens to rely on their values will break. > > At which point we'll handle complaints by pointing and laughing. > > > > It's a 9P bug; fix it there. Turning random internal constants into a part > > of ABI is not going to work. > > Signed-off-by: Sasha Levin <levinsasha928@gmail.com> > --- > fs/9p/vfs_inode_dotl.c | 31 ++++++++++++++++++++++++++++++- > include/net/9p/9p.h | 18 ++++++++++++++++++ > 2 files changed, 48 insertions(+), 1 deletions(-) > > diff --git a/fs/9p/vfs_inode_dotl.c b/fs/9p/vfs_inode_dotl.c > index 0b5745e..a948214 100644 > --- a/fs/9p/vfs_inode_dotl.c > +++ b/fs/9p/vfs_inode_dotl.c > @@ -523,6 +523,35 @@ v9fs_vfs_getattr_dotl(struct vfsmount *mnt, struct dentry *dentry, > return 0; > } > > +int v9fs_vfs_iattr_to_9p_valid(u32 ia_valid) > +{ > + u32 valid = 0, i; > + static u32 attr_map[][2] = { > + {ATTR_MODE, P9_ATTR_MODE}, > + {ATTR_UID, P9_ATTR_UID}, > + {ATTR_SIZE, P9_ATTR_SIZE}, > + {ATTR_ATIME, P9_ATTR_ATIME}, > + {ATTR_MTIME, P9_ATTR_MTIME}, > + {ATTR_CTIME, P9_ATTR_CTIME}, > + {ATTR_ATIME_SET, P9_ATTR_ATIME_SET}, > + {ATTR_MTIME_SET, P9_ATTR_MTIME_SET}, > + {ATTR_FORCE, P9_ATTR_FORCE}, > + {ATTR_ATTR_FLAG, P9_ATTR_ATTR_FLAG}, > + {ATTR_KILL_SUID, P9_ATTR_KILL_SUID}, > + {ATTR_KILL_SGID, P9_ATTR_KILL_SGID}, > + {ATTR_FILE, P9_ATTR_FILE}, > + {ATTR_KILL_PRIV, P9_ATTR_KILL_PRIV}, > + {ATTR_OPEN, P9_ATTR_OPEN}, > + {ATTR_TIMES_SET, P9_ATTR_TIMES_SET}, > + }; a) ATTR_GID is lost b) passing ATTR_FILE is bloody pointless; look at what it does and realize that 9p doesn't as much as look at ia_file. c) ATTR_KILL_PRIV is very dubious; what's the legitimate use of that puppy in fs code? Look, that's the problem with exposing this stuff to protocol; you don't get clear semantics and are you seriously asking for trouble on kernel changes. Suppose tomorrow we get rid of e.g. ATTR_KILL_PRIV; what are you guys going to do? Hope that no 9p server has behaviour dependent on that flag being set or cleared? Don't turn the kernel internals into a part of ABI. And blind bulk remapping of constants is exactly that... -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Sat, 2011-12-17 at 17:47 +0000, Al Viro wrote: > Look, that's the problem with exposing this stuff to protocol; you don't > get clear semantics and are you seriously asking for trouble on kernel > changes. Suppose tomorrow we get rid of e.g. ATTR_KILL_PRIV; what are you > guys going to do? Hope that no 9p server has behaviour dependent on that > flag being set or cleared? > > Don't turn the kernel internals into a part of ABI. And blind bulk remapping > of constants is exactly that... I went with Aneesh's suggestion and did something similar to something 9p already has done before. This is probably a good opportunity to open it up for discussion, since I currently have a block of code containing those ATTR_* defines copy-pasted from linux/fs.h in my userspace code, and thats obviously a serious wtf.
diff --git a/fs/9p/vfs_inode_dotl.c b/fs/9p/vfs_inode_dotl.c index 0b5745e..a948214 100644 --- a/fs/9p/vfs_inode_dotl.c +++ b/fs/9p/vfs_inode_dotl.c @@ -523,6 +523,35 @@ v9fs_vfs_getattr_dotl(struct vfsmount *mnt, struct dentry *dentry, return 0; } +int v9fs_vfs_iattr_to_9p_valid(u32 ia_valid) +{ + u32 valid = 0, i; + static u32 attr_map[][2] = { + {ATTR_MODE, P9_ATTR_MODE}, + {ATTR_UID, P9_ATTR_UID}, + {ATTR_SIZE, P9_ATTR_SIZE}, + {ATTR_ATIME, P9_ATTR_ATIME}, + {ATTR_MTIME, P9_ATTR_MTIME}, + {ATTR_CTIME, P9_ATTR_CTIME}, + {ATTR_ATIME_SET, P9_ATTR_ATIME_SET}, + {ATTR_MTIME_SET, P9_ATTR_MTIME_SET}, + {ATTR_FORCE, P9_ATTR_FORCE}, + {ATTR_ATTR_FLAG, P9_ATTR_ATTR_FLAG}, + {ATTR_KILL_SUID, P9_ATTR_KILL_SUID}, + {ATTR_KILL_SGID, P9_ATTR_KILL_SGID}, + {ATTR_FILE, P9_ATTR_FILE}, + {ATTR_KILL_PRIV, P9_ATTR_KILL_PRIV}, + {ATTR_OPEN, P9_ATTR_OPEN}, + {ATTR_TIMES_SET, P9_ATTR_TIMES_SET}, + }; + + for (i = 0; i < ARRAY_SIZE(attr_map); i++) + if (ia_valid & attr_map[i][0]) + valid |= attr_map[i][1]; + + return valid; +} + /** * v9fs_vfs_setattr_dotl - set file metadata * @dentry: file whose metadata to set @@ -543,7 +572,7 @@ int v9fs_vfs_setattr_dotl(struct dentry *dentry, struct iattr *iattr) if (retval) return retval; - p9attr.valid = iattr->ia_valid; + p9attr.valid = v9fs_vfs_iattr_to_9p_valid(iattr->ia_valid); p9attr.mode = iattr->ia_mode; p9attr.uid = iattr->ia_uid; p9attr.gid = iattr->ia_gid; diff --git a/include/net/9p/9p.h b/include/net/9p/9p.h index 2d70b95..98b3f71 100644 --- a/include/net/9p/9p.h +++ b/include/net/9p/9p.h @@ -468,6 +468,24 @@ struct p9_stat_dotl { #define P9_STATS_BASIC 0x000007ffULL /* Mask for fields up to BLOCKS */ #define P9_STATS_ALL 0x00003fffULL /* Mask for All fields above */ +#define P9_ATTR_MODE (1 << 0) +#define P9_ATTR_UID (1 << 1) +#define P9_ATTR_GID (1 << 2) +#define P9_ATTR_SIZE (1 << 3) +#define P9_ATTR_ATIME (1 << 4) +#define P9_ATTR_MTIME (1 << 5) +#define P9_ATTR_CTIME (1 << 6) +#define P9_ATTR_ATIME_SET (1 << 7) +#define P9_ATTR_MTIME_SET (1 << 8) +#define P9_ATTR_FORCE (1 << 9) /* Not a change, but a change it */ +#define P9_ATTR_ATTR_FLAG (1 << 10) +#define P9_ATTR_KILL_SUID (1 << 11) +#define P9_ATTR_KILL_SGID (1 << 12) +#define P9_ATTR_FILE (1 << 13) +#define P9_ATTR_KILL_PRIV (1 << 14) +#define P9_ATTR_OPEN (1 << 15) /* Truncating from open(O_TRUNC) */ +#define P9_ATTR_TIMES_SET (1 << 16) + /** * struct p9_iattr_dotl - P9 inode attribute for setattr * @valid: bitfield specifying which fields are valid