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Message-ID: <AANLkTilJVYGllPB5I2lG_MPWgxYSJmHh4dproHx563kT@mail.gmail.com>
Date: Sun, 4 Jul 2010 06:27:30 +0200
From: Michael Kerrisk <mtk.manpages@...il.com>
To: David Howells <dhowells@...hat.com>
Cc: linux-fsdevel@...r.kernel.org, linux-cifs@...r.kernel.org,
linux-kernel@...r.kernel.org, samba-technical@...ts.samba.org,
linux-ext4@...r.kernel.org, linux-api@...r.kernel.org
Subject: Re: [PATCH 3/3] xstat: Implement a requestable extra result to
procure some inode flags [ver #4]
[CC+=linux-api]
On Fri, Jul 2, 2010 at 1:57 AM, David Howells <dhowells@...hat.com> wrote:
> [This is, for the moment, to be considered an example. Do we actually want to
> export these flags? Should they be a full member of struct xstat?]
Since I suggested the idea, obviously I'm inclined to think they should ;-).
Cheers,
Michael
> Allow an extra result to be requested that makes available some inode flags,
> along the lines of BSD's st_flags and Ext2/3/4's inode flags. This is
> requested by setting XSTAT_REQUEST_INODE_FLAGS in the request_mask. If the
> filesystem supports it for that file, then this will be set in result_mask and
> 16 bytes of information will be appended to the xstat buffer, if sufficient
> buffer space is available.
>
> The extra result is laid out according to the following structure:
>
> struct xstat_inode_flags {
> unsigned long long st_flags;
> unsigned long long st_supported_flags;
> };
>
> where the filesystem indicates the flags it supports for that file and the
> flags that are set on that file. The structure is of length:
>
> XSTAT_LENGTH_INODE_FLAGS
>
> The flags come in three sets:
>
> (1) User settable flags (to be consistent with the BSD st_flags field):
>
> UF_NODUMP Do not dump this file.
> UF_IMMUTABLE This file is immutable.
> UF_APPEND This file is append-only.
> UF_OPAQUE This directory is opaque (unionfs).
> UF_NOUNLINK This file can't be removed or renamed.
> UF_COMPRESSED This file is compressed.
> UF_HIDDEN This file shouldn't be displayed in a GUI.
>
> The UF_SETTABLE constant is the union of the above flags.
>
> (2) Superuser settable flags (to be consistent with the BSD st_flags field):
>
> SF_ARCHIVED This file has been archived.
> SF_IMMUTABLE This file is immutable.
> SF_APPEND This file is append-only.
> SF_NOUNLINK This file can't be removed or renamed.
> SF_HIDDEN This file is a snapshot inode.
>
> The SF_SETTABLE constant is the union of the above flags.
>
> (3) Linux-specific flags:
>
> XSTAT_LF_MAGIC_FILE Magic file, such as found in procfs and sysfs.
> XSTAT_LF_SYNC File is written synchronously.
> XSTAT_LF_NOATIME Atime is not updated on this file.
> XSTAT_LF_JOURNALLED_DATA Data modifications to this file are journalled.
> XSTAT_LF_ENCRYPTED This file is encrypted.
> XSTAT_LF_SYSTEM This file is a system file (FAT/NTFS/CIFS).
> XSTAT_LF_TEMPORARY This file is a temporary file (NTFS/CIFS).
> XSTAT_LF_OFFLINE file is currently unavailable (CIFS).
>
>
> The Ext4 filesystem has been modified to map certain Ext4 inode flags to the
> above:
>
> EXT4 FLAG MAPPED TO
> ======================= =======================================
> EXT4_COMPR_FL UF_COMPRESSED
> EXT4_SYNC_FL XSTAT_LF_SYNC
> EXT4_IMMUTABLE_FL UF_IMMUTABLE and SF_IMMUTABLE
> EXT4_APPEND_FL UF_APPEND and SF_APPEND
> EXT4_NODUMP_FL UF_NODUMP
> EXT4_NOATIME_FL XSTAT_LF_NOATIME
> EXT4_JOURNAL_DATA_FL XSTAT_LF_JOURNALLED_DATA
> EXT4_DIRSYNC_FL XSTAT_LF_SYNC (directories only)
>
> With this patch applied, the test program given in the patch that introduced
> the xstat() syscalls now does this:
>
> [root@...romeda ~]# chattr +ia /var/cache/fscache/cull_atimes
> [root@...romeda ~]# lsattr /var/cache/fscache/cull_atimes
> ----ia-------e- /var/cache/fscache/cull_atimes
> [root@...romeda ~]# /tmp/xstat /var/cache/fscache/cull_atimes
> xstat(/var/cache/fscache/cull_atimes) = 168
> results=5fef
> Size: 78088 Blocks: 168 IO Block: 4096 regular file
> Device: 08:06 Inode: 13 Links: 1
> Access: (0600/-rw-------) Uid: 0
> Gid: 0
> Access: 2010-06-29 18:17:41.092290108+0100
> Modify: 2010-06-25 17:25:53.320261493+0100
> Change: 2010-07-02 00:46:51.278803967+0100
> Create: 2010-06-25 15:17:39.711172889+0100
> Inode version: f585ab73h
> 0098: 0000000000060006 0000000e00060027
>
> The extra results are hex dumped at the end in 64-bit chunks. As can be seen
> above, st_flags=0x0000000000060006 and st_supported_flags=0000000e00060027.
> That's showing that the file now has [SU]F_IMMUTABLE and [SU]F_APPEND enabled.
>
> Note also that XSTAT_REQUEST_INODE_FLAGS (0x4000) is present in the result_mask
> value (0x5fef) returned to userspace, and the amount of data returned by
> xstat() has increased from 152 to 168 as appropriate for 16 bytes of extra
> data.
>
> Signed-off-by: David Howells <dhowells@...hat.com>
> ---
>
> fs/ext4/ext4.h | 2 ++
> fs/ext4/file.c | 1 +
> fs/ext4/inode.c | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++
> fs/ext4/namei.c | 2 ++
> fs/ext4/symlink.c | 2 ++
> include/linux/stat.h | 47 ++++++++++++++++++++++++++++++++++++++++++++++-
> 6 files changed, 103 insertions(+), 1 deletions(-)
>
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index 96823f3..26b8dd6 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -1573,6 +1573,8 @@ extern int ext4_getattr(struct vfsmount *mnt, struct dentry *dentry,
> struct kstat *stat);
> extern int ext4_file_getattr(struct vfsmount *mnt, struct dentry *dentry,
> struct kstat *stat);
> +extern int ext4_getattr_extra(struct vfsmount *, struct dentry *,
> + struct xstat_extra_result *);
> extern void ext4_delete_inode(struct inode *);
> extern int ext4_sync_inode(handle_t *, struct inode *);
> extern void ext4_dirty_inode(struct inode *);
> diff --git a/fs/ext4/file.c b/fs/ext4/file.c
> index 18c29ab..657ffa0 100644
> --- a/fs/ext4/file.c
> +++ b/fs/ext4/file.c
> @@ -151,6 +151,7 @@ const struct inode_operations ext4_file_inode_operations = {
> .truncate = ext4_truncate,
> .setattr = ext4_setattr,
> .getattr = ext4_file_getattr,
> + .getattr_extra = ext4_getattr_extra,
> #ifdef CONFIG_EXT4_FS_XATTR
> .setxattr = generic_setxattr,
> .getxattr = generic_getxattr,
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index f9a730a..efa17d6 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -5595,6 +5595,56 @@ int ext4_file_getattr(struct vfsmount *mnt, struct dentry *dentry,
> return 0;
> }
>
> +int ext4_getattr_inode_flags(struct inode *inode,
> + struct xstat_extra_result *extra)
> +{
> + struct ext4_inode_info *ei = EXT4_I(inode);
> + struct xstat_inode_flags xif = { 0, 0 };
> +
> +#define _(FL, ST) \
> + xif.st_supported_flags |= ST; \
> + if (ei->i_flags & FL) \
> + xif.st_flags |= ST;
> +
> + _(EXT4_COMPR_FL, UF_COMPRESSED);
> + _(EXT4_SYNC_FL, XSTAT_LF_SYNC);
> + _(EXT4_IMMUTABLE_FL, UF_IMMUTABLE | SF_IMMUTABLE);
> + _(EXT4_APPEND_FL, UF_APPEND | SF_APPEND);
> + _(EXT4_NODUMP_FL, UF_NODUMP);
> + _(EXT4_NOATIME_FL, XSTAT_LF_NOATIME);
> + _(EXT4_JOURNAL_DATA_FL, XSTAT_LF_JOURNALLED_DATA);
> +
> + if (S_ISDIR(ei->vfs_inode.i_mode))
> + _(EXT4_DIRSYNC_FL, XSTAT_LF_SYNC);
> +
> + return extra->pass_result(extra, ilog2(XSTAT_REQUEST_INODE_FLAGS),
> + &xif, sizeof(xif));
> +}
> +
> +int ext4_getattr_extra(struct vfsmount *mnt, struct dentry *dentry,
> + struct xstat_extra_result *extra)
> +{
> + struct inode *inode = dentry->d_inode;
> + u64 request_mask = extra->request_mask;
> + int request, ret;
> +
> + do {
> + request = __ffs64(request_mask);
> + request_mask &= ~(1ULL << request);
> +
> + switch (request) {
> + case ilog2(XSTAT_REQUEST_INODE_FLAGS):
> + ret = ext4_getattr_inode_flags(inode, extra);
> + break;
> + default:
> + ret = 0;
> + break;
> + }
> +
> + } while (ret == 0 && request_mask);
> + return ret;
> +}
> +
> static int ext4_indirect_trans_blocks(struct inode *inode, int nrblocks,
> int chunk)
> {
> diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
> index 0f776c7..3c37b3f 100644
> --- a/fs/ext4/namei.c
> +++ b/fs/ext4/namei.c
> @@ -2543,6 +2543,7 @@ const struct inode_operations ext4_dir_inode_operations = {
> .rename = ext4_rename,
> .setattr = ext4_setattr,
> .getattr = ext4_getattr,
> + .getattr_extra = ext4_getattr_extra,
> #ifdef CONFIG_EXT4_FS_XATTR
> .setxattr = generic_setxattr,
> .getxattr = generic_getxattr,
> @@ -2556,6 +2557,7 @@ const struct inode_operations ext4_dir_inode_operations = {
> const struct inode_operations ext4_special_inode_operations = {
> .setattr = ext4_setattr,
> .getattr = ext4_getattr,
> + .getattr_extra = ext4_getattr_extra,
> #ifdef CONFIG_EXT4_FS_XATTR
> .setxattr = generic_setxattr,
> .getxattr = generic_getxattr,
> diff --git a/fs/ext4/symlink.c b/fs/ext4/symlink.c
> index d8fe7fb..8c206b2 100644
> --- a/fs/ext4/symlink.c
> +++ b/fs/ext4/symlink.c
> @@ -36,6 +36,7 @@ const struct inode_operations ext4_symlink_inode_operations = {
> .put_link = page_put_link,
> .setattr = ext4_setattr,
> .getattr = ext4_getattr,
> + .getattr_extra = ext4_getattr_extra,
> #ifdef CONFIG_EXT4_FS_XATTR
> .setxattr = generic_setxattr,
> .getxattr = generic_getxattr,
> @@ -49,6 +50,7 @@ const struct inode_operations ext4_fast_symlink_inode_operations = {
> .follow_link = ext4_follow_link,
> .setattr = ext4_setattr,
> .getattr = ext4_getattr,
> + .getattr_extra = ext4_getattr_extra,
> #ifdef CONFIG_EXT4_FS_XATTR
> .setxattr = generic_setxattr,
> .getxattr = generic_getxattr,
> diff --git a/include/linux/stat.h b/include/linux/stat.h
> index 9e27f88..4c87878 100644
> --- a/include/linux/stat.h
> +++ b/include/linux/stat.h
> @@ -107,7 +107,8 @@ struct xstat_parameters {
> #define XSTAT_REQUEST_GEN 0x00001000ULL /* want/got st_gen */
> #define XSTAT_REQUEST_DATA_VERSION 0x00002000ULL /* want/got st_data_version */
> #define XSTAT_REQUEST__EXTENDED_STATS 0x00003fffULL /* the stuff in the xstat struct */
> -#define XSTAT_REQUEST__ALL_STATS 0x00003fffULL /* the defined set of requestables */
> +#define XSTAT_REQUEST_INODE_FLAGS 0x00004000ULL /* want/got xstat_inode_flags */
> +#define XSTAT_REQUEST__ALL_STATS 0x00007fffULL /* the defined set of requestables */
> #define XSTAT_REQUEST__EXTRA_STATS (XSTAT_REQUEST__ALL_STATS & ~XSTAT_REQUEST__EXTENDED_STATS)
> };
>
> @@ -140,6 +141,50 @@ struct xstat {
> unsigned long long st_extra_results[0]; /* extra requested results */
> };
>
> +/*
> + * Extra result field for inode flags (XSTAT_REQUEST_INODE_FLAGS)
> + */
> +struct xstat_inode_flags {
> + /* Flags set on the file
> + * - the LSW matches the BSD st_flags
> + * - the MSW are Linux-specific
> + */
> + unsigned long long st_flags;
> + /* st_flags that users can set */
> +#define UF_SETTABLE 0x0000ffff
> +#define UF_NODUMP 0x00000001 /* do not dump */
> +#define UF_IMMUTABLE 0x00000002 /* immutable */
> +#define UF_APPEND 0x00000004 /* append-only */
> +#define UF_OPAQUE 0x00000008 /* directory is opaque (unionfs) */
> +#define UF_NOUNLINK 0x00000010 /* can't be removed or renamed */
> +#define UF_COMPRESSED 0x00000020 /* file is compressed */
> +#define UF_HIDDEN 0x00008000 /* file shouldn't be displayed in a GUI */
> +
> + /* st_flags that only root can set */
> +#define SF_SETTABLE 0xffff0000
> +#define SF_ARCHIVED 0x00010000 /* archived */
> +#define SF_IMMUTABLE 0x00020000 /* immutable */
> +#define SF_APPEND 0x00040000 /* append-only */
> +#define SF_NOUNLINK 0x00100000 /* can't be removed or renamed */
> +#define SF_SNAPSHOT 0x00200000 /* snapshot inode */
> +
> + /* Linux-specific st_flags */
> +#define XSTAT_LF_MAGIC_FILE (1ULL << 32) /* magic file, such as /proc/? and /sys/? */
> +#define XSTAT_LF_SYNC (1ULL << 33) /* file is written synchronously */
> +#define XSTAT_LF_NOATIME (1ULL << 34) /* atime is not updated on file */
> +#define XSTAT_LF_JOURNALLED_DATA (1ULL << 35) /* data modifications to file are journalled */
> +#define XSTAT_LF_ENCRYPTED (1ULL << 36) /* file is encrypted */
> +#define XSTAT_LF_SYSTEM (1ULL << 37) /* system file */
> +#define XSTAT_LF_TEMPORARY (1ULL << 38) /* temporary file */
> +#define XSTAT_LF_OFFLINE (1ULL << 39) /* file is currently unavailable */
> +
> + /* Which st_flags are actually supported by this filesystem for this
> + * file */
> + unsigned long long st_supported_flags;
> +};
> +#define XSTAT_LENGTH_INODE_FLAGS (sizeof(struct xstat_inode_flags))
> +
> +
> #ifdef __KERNEL__
> #define S_IRWXUGO (S_IRWXU|S_IRWXG|S_IRWXO)
> #define S_IALLUGO (S_ISUID|S_ISGID|S_ISVTX|S_IRWXUGO)
>
> --
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--
Michael Kerrisk Linux man-pages maintainer;
http://www.kernel.org/doc/man-pages/
Author of "The Linux Programming Interface", http://blog.man7.org/
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