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Date: Fri, 20 Nov 2015 08:50:22 -0800 From: Casey Schaufler <casey@...aufler-ca.com> To: David Howells <dhowells@...hat.com>, arnd@...db.de Cc: linux-afs@...r.kernel.org, linux-nfs@...r.kernel.org, linux-cifs@...r.kernel.org, samba-technical@...ts.samba.org, linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org Subject: Re: [RFC][PATCH 00/12] Enhanced file stat system call On 11/20/2015 6:54 AM, David Howells wrote: > Implement new system calls to provide enhanced file stats and enhanced > filesystem stats. The patches can be found here: > > http://git.kernel.org/cgit/linux/kernel/git/dhowells/linux-fs.git/log/?h=xstat > > > =========== > DESCRIPTION > =========== > > The third patch provides this new system call: > > long ret = statx(int dfd, > const char *filename, > unsigned atflag, > unsigned mask, > struct statx *buffer); > > This is an enhanced file stat function that provides a number of useful > features, in summary: > > (1) More information: creation time, data version number, > flags/attributes. A subset of these is available through a number of > filesystems (such as CIFS, NFS, AFS, Ext4 and BTRFS). > > (2) Lightweight stat (AT_NO_ATTR_SYNC): Ask for just those details of > interest, and allow a network fs to approximate anything not of > interest, without going to the server. > > (3) Heavyweight stat (AT_FORCE_ATTR_SYNC): Force a network fs to flush > buffers and go to the server, even if it thinks its cached attributes > are up to date. > > (4) Allow the filesystem to indicate what it can/cannot provide: A > filesystem can now say it doesn't support a standard stat feature if > that isn't available. > > (5) Make the fields a consistent size on all arches, and make them large. > > (6) Can be extended by using more request flags and using up the padding > space in the statx struct. How about relevant xattrs? SELinux context, ACL, that sort of thing. The fact that these are optional should be taken care of by (4). > > Note that no lstat() equivalent is required as that can be implemented > through statx() with atflag == 0. There is also no fstat() equivalent as > that can be implemented through statx() with filename == NULL and the > relevant fd passed as dfd. > > > The seventh patch provides another new system call: > > long ret = fsinfo(int dfd, > const char *filename, > unsigned atflag, > unsigned request, > void *buffer); > > This is an enhanced filesystem stat and information retrieval function that > provides more information, in summary: > > (1) All the information provided by statfs() and more. The fields are > made large. > > (2) Provides information about timestamp range and resolution to > complement statx(). > > (3) Provides information about IOC flags supported in statx()'s return. > > (4) Provides volume binary IDs and UUIDs. > > (5) Provides the filesystem name according to the kernel as a string > (eg. "ext4" or "nfs3") in addition to the magic number. > > (6) Provides information obtained from network filesystems, such as volume > and domain names. > > (7) Has lots of spare space that can be used for future extenstions and a > bit mask indicating what was provided. > > Note that I've added a 'request' identifier. This is to select the set of > data to be returned. The idea is that 'buffer' points to a fixed-size > struct selected by request. Currently only 0 is available and this refers > to 'struct fsinfo'. However, I could split up the buffer into say 3: > > (0) statfs-type information > > (1) Timestamp and IOC flags info. > > (2) Network fs strings. > > However, some of this might be better retrieved through getxattr(). > > > ======= > TESTING > ======= > > Test programs are added into samples/statx/ by the appropriate patches. > > David > --- > David Howells (12): > Ext4: Fix extended timestamp encoding and decoding > statx: Provide IOC flags for Windows fs attributes > statx: Add a system call to make enhanced file info available > statx: AFS: Return enhanced file attributes > statx: Ext4: Return enhanced file attributes > statx: NFS: Return enhanced file attributes > statx: CIFS: Return enhanced attributes > fsinfo: Add a system call to make enhanced filesystem info available > fsinfo: Ext4: Return information through the filesystem info syscall > fsinfo: AFS: Return information through the filesystem info syscall > fsinfo: NFS: Return information through the filesystem info syscall > fsinfo: CIFS: Return information through the filesystem info syscall > > > arch/x86/entry/syscalls/syscall_32.tbl | 2 > arch/x86/entry/syscalls/syscall_64.tbl | 2 > fs/afs/inode.c | 23 ++ > fs/afs/super.c | 39 ++++ > fs/cifs/cifsfs.c | 25 +++ > fs/cifs/cifsfs.h | 4 > fs/cifs/cifsglob.h | 8 + > fs/cifs/dir.c | 2 > fs/cifs/inode.c | 124 ++++++++++--- > fs/cifs/netmisc.c | 4 > fs/exportfs/expfs.c | 4 > fs/ext4/ext4.h | 24 ++- > fs/ext4/file.c | 2 > fs/ext4/inode.c | 31 +++ > fs/ext4/namei.c | 2 > fs/ext4/super.c | 39 ++++ > fs/ext4/symlink.c | 2 > fs/nfs/inode.c | 45 ++++- > fs/nfs/internal.h | 1 > fs/nfs/nfs4super.c | 1 > fs/nfs/super.c | 58 ++++++ > fs/ntfs/time.h | 2 > fs/stat.c | 305 +++++++++++++++++++++++++++++--- > fs/statfs.c | 218 +++++++++++++++++++++++ > include/linux/fs.h | 7 + > include/linux/stat.h | 14 + > include/linux/syscalls.h | 6 + > include/linux/time64.h | 2 > include/uapi/linux/fcntl.h | 2 > include/uapi/linux/fs.h | 7 + > include/uapi/linux/stat.h | 185 +++++++++++++++++++ > samples/Makefile | 3 > samples/statx/Makefile | 13 + > samples/statx/test-fsinfo.c | 179 +++++++++++++++++++ > samples/statx/test-statx.c | 273 +++++++++++++++++++++++++++++ > 35 files changed, 1558 insertions(+), 100 deletions(-) > create mode 100644 samples/statx/Makefile > create mode 100644 samples/statx/test-fsinfo.c > create mode 100644 samples/statx/test-statx.c > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@...r.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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