Re: [uml-devel] [PATCH] Make hostfs_setattr() support operations on closed files.

[Alberto Bertogli <albertito@gmail.com>]

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On Tue, Apr 24, 2007 at 11:26:26AM -0300, Alberto Bertogli wrote:
> This patch allows hostfs_setattr() to work on closed files by calling
> set_attr() (the userspace part) with the inode's fd.
>
[...]
> 
>  fs/hostfs/hostfs.h      |    4 +-
>  fs/hostfs/hostfs_kern.c |   10 ++++-
>  fs/hostfs/hostfs_user.c |   89 ++++++++++++++++++++++++++++++++++++++++-------
>  3 files changed, 86 insertions(+), 17 deletions(-)

Here (as an inline attachment) is the updated patch that (hopefully)
address Blaisorblade's comments.

Thanks,
		Alberto



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From af922e915c05e32f0392b234e047f9aa9857fb80 Mon Sep 17 00:00:00 2001
From: Alberto Bertogli <albertito@gmail.com>
Date: Thu, 26 Apr 2007 01:57:07 -0300
Subject: [PATCH] Make hostfs_setattr() support operations on unlinked open files.

This patch allows hostfs_setattr() to work on unlinked open files by
calling set_attr() (the userspace part) with the inode's fd.

Without this, applications that depend on doing attribute changes to
unlinked open files will fail.

It works by using the fd versions instead of the path ones (for example
fchmod() instead of chmod(), fchown() instead of chown()) when an fd is
available.

Signed-off-by: Alberto Bertogli <albertito@gmail.com>
---
 fs/hostfs/hostfs.h      |    4 +-
 fs/hostfs/hostfs_kern.c |    6 ++-
 fs/hostfs/hostfs_user.c |  108 +++++++++++++++++++++++++++++-----------------
 3 files changed, 74 insertions(+), 44 deletions(-)

diff --git a/fs/hostfs/hostfs.h b/fs/hostfs/hostfs.h
index 70543b1..d8850c7 100644
--- a/fs/hostfs/hostfs.h
+++ b/fs/hostfs/hostfs.h
@@ -55,7 +55,7 @@ extern int stat_file(const char *path, unsigned long long *inode_out,
 		     int *mode_out, int *nlink_out, int *uid_out, int *gid_out,
 		     unsigned long long *size_out, struct timespec *atime_out,
 		     struct timespec *mtime_out, struct timespec *ctime_out,
-		     int *blksize_out, unsigned long long *blocks_out);
+		     int *blksize_out, unsigned long long *blocks_out, int fd);
 extern int access_file(char *path, int r, int w, int x);
 extern int open_file(char *path, int r, int w, int append);
 extern int file_type(const char *path, int *maj, int *min);
@@ -71,7 +71,7 @@ extern int lseek_file(int fd, long long offset, int whence);
 extern int fsync_file(int fd, int datasync);
 extern int file_create(char *name, int ur, int uw, int ux, int gr,
 		       int gw, int gx, int or, int ow, int ox);
-extern int set_attr(const char *file, struct hostfs_iattr *attrs);
+extern int set_attr(const char *file, struct hostfs_iattr *attrs, int fd);
 extern int make_symlink(const char *from, const char *to);
 extern int unlink_file(const char *file);
 extern int do_mkdir(const char *file, int mode);
diff --git a/fs/hostfs/hostfs_kern.c b/fs/hostfs/hostfs_kern.c
index fd301a9..4e8bb2f 100644
--- a/fs/hostfs/hostfs_kern.c
+++ b/fs/hostfs/hostfs_kern.c
@@ -147,7 +147,7 @@ static int read_name(struct inode *ino, char *name)
 
 	err = stat_file(name, &i_ino, &i_mode, &i_nlink, &ino->i_uid,
 			&ino->i_gid, &i_size, &ino->i_atime, &ino->i_mtime,
-			&ino->i_ctime, &i_blksize, &i_blocks);
+			&ino->i_ctime, &i_blksize, &i_blocks, -1);
 	if(err)
 		return(err);
 
@@ -820,6 +820,8 @@ int hostfs_setattr(struct dentry *dentry, struct iattr *attr)
 	char *name;
 	int err;
 
+	int fd = HOSTFS_I(dentry->d_inode)->fd;
+
 	err = inode_change_ok(dentry->d_inode, attr);
 	if (err)
 		return err;
@@ -864,7 +866,7 @@ int hostfs_setattr(struct dentry *dentry, struct iattr *attr)
 	}
 	name = dentry_name(dentry, 0);
 	if(name == NULL) return(-ENOMEM);
-	err = set_attr(name, &attrs);
+	err = set_attr(name, &attrs, fd);
 	kfree(name);
 	if(err)
 		return(err);
diff --git a/fs/hostfs/hostfs_user.c b/fs/hostfs/hostfs_user.c
index 1ed5ea3..0acf562 100644
--- a/fs/hostfs/hostfs_user.c
+++ b/fs/hostfs/hostfs_user.c
@@ -21,12 +21,16 @@ int stat_file(const char *path, unsigned long long *inode_out, int *mode_out,
 	      int *nlink_out, int *uid_out, int *gid_out,
 	      unsigned long long *size_out, struct timespec *atime_out,
 	      struct timespec *mtime_out, struct timespec *ctime_out,
-	      int *blksize_out, unsigned long long *blocks_out)
+	      int *blksize_out, unsigned long long *blocks_out, int fd)
 {
 	struct stat64 buf;
 
-	if(lstat64(path, &buf) < 0)
+	if(fd >= 0) {
+		if (fstat64(fd, &buf) < 0)
+			return(-errno);
+	} else if(lstat64(path, &buf) < 0) {
 		return(-errno);
+	}
 
 	if(inode_out != NULL) *inode_out = buf.st_ino;
 	if(mode_out != NULL) *mode_out = buf.st_mode;
@@ -202,58 +206,82 @@ int file_create(char *name, int ur, int uw, int ux, int gr,
 	return(fd);
 }
 
-int set_attr(const char *file, struct hostfs_iattr *attrs)
+int set_attr(const char *file, struct hostfs_iattr *attrs, int fd)
 {
-	struct utimbuf buf;
+	struct timeval times[2];
+	struct timespec atime_ts, mtime_ts;
 	int err, ma;
 
-	if(attrs->ia_valid & HOSTFS_ATTR_MODE){
-		if(chmod(file, attrs->ia_mode) != 0) return(-errno);
-	}
-	if(attrs->ia_valid & HOSTFS_ATTR_UID){
-		if(chown(file, attrs->ia_uid, -1)) return(-errno);
+	if (attrs->ia_valid & HOSTFS_ATTR_MODE) {
+		if (fd >= 0) {
+			if (fchmod(fd, attrs->ia_mode) != 0)
+				return (-errno);
+		} else if (chmod(file, attrs->ia_mode) != 0) {
+			return (-errno);
+		}
 	}
-	if(attrs->ia_valid & HOSTFS_ATTR_GID){
-		if(chown(file, -1, attrs->ia_gid)) return(-errno);
+	if (attrs->ia_valid & HOSTFS_ATTR_UID) {
+		if (fd >= 0) {
+			if (fchown(fd, attrs->ia_uid, -1))
+				return (-errno);
+		} else if(chown(file, attrs->ia_uid, -1)) {
+			return (-errno);
+		}
 	}
-	if(attrs->ia_valid & HOSTFS_ATTR_SIZE){
-		if(truncate(file, attrs->ia_size)) return(-errno);
+	if (attrs->ia_valid & HOSTFS_ATTR_GID) {
+		if (fd >= 0) {
+			if (fchown(fd, -1, attrs->ia_gid))
+				return (-errno);
+		} else if (chown(file, -1, attrs->ia_gid)) {
+			return (-errno);
+		}
 	}
-	ma = HOSTFS_ATTR_ATIME_SET | HOSTFS_ATTR_MTIME_SET;
-	if((attrs->ia_valid & ma) == ma){
-		buf.actime = attrs->ia_atime.tv_sec;
-		buf.modtime = attrs->ia_mtime.tv_sec;
-		if(utime(file, &buf) != 0) return(-errno);
+	if (attrs->ia_valid & HOSTFS_ATTR_SIZE) {
+		if (fd >= 0) {
+			if (ftruncate(fd, attrs->ia_size))
+				return (-errno);
+		} else if (truncate(file, attrs->ia_size)) {
+			return (-errno);
+		}
 	}
-	else {
-		struct timespec ts;
-
-		if(attrs->ia_valid & HOSTFS_ATTR_ATIME_SET){
-			err = stat_file(file, NULL, NULL, NULL, NULL, NULL,
-					NULL, NULL, &ts, NULL, NULL, NULL);
-			if(err != 0)
-				return(err);
-			buf.actime = attrs->ia_atime.tv_sec;
-			buf.modtime = ts.tv_sec;
-			if(utime(file, &buf) != 0)
-				return(-errno);
+
+	/* Update accessed and/or modified time, in two parts: first set
+	 * times according to the changes to perform, and then call futimes()
+	 * or utimes() to apply them. */
+	ma = (HOSTFS_ATTR_ATIME_SET | HOSTFS_ATTR_MTIME_SET);
+	if (attrs->ia_valid & ma) {
+		err = stat_file(file, NULL, NULL, NULL, NULL, NULL, NULL,
+				&atime_ts, &mtime_ts, NULL, NULL, NULL, fd);
+		if (err != 0)
+			return err;
+
+		times[0].tv_sec = atime_ts.tv_sec;
+		times[0].tv_usec = atime_ts.tv_nsec * 1000;
+		times[1].tv_sec = mtime_ts.tv_sec;
+		times[1].tv_usec = mtime_ts.tv_nsec * 1000;
+
+		if (attrs->ia_valid & HOSTFS_ATTR_ATIME_SET) {
+			times[0].tv_sec = attrs->ia_atime.tv_sec;
+			times[0].tv_usec = attrs->ia_atime.tv_nsec * 1000;
 		}
-		if(attrs->ia_valid & HOSTFS_ATTR_MTIME_SET){
-			err = stat_file(file, NULL, NULL, NULL, NULL, NULL,
-					NULL, &ts, NULL, NULL, NULL, NULL);
-			if(err != 0)
-				return(err);
-			buf.actime = ts.tv_sec;
-			buf.modtime = attrs->ia_mtime.tv_sec;
-			if(utime(file, &buf) != 0)
-				return(-errno);
+		if (attrs->ia_valid & HOSTFS_ATTR_MTIME_SET) {
+			times[1].tv_sec = attrs->ia_mtime.tv_sec;
+			times[1].tv_usec = attrs->ia_mtime.tv_nsec * 1000;
+		}
+
+		if (fd >= 0) {
+			if (futimes(fd, times) != 0)
+				return (-errno);
+		} else if (utimes(file, times) != 0) {
+			return (-errno);
 		}
 	}
+
 	if(attrs->ia_valid & HOSTFS_ATTR_CTIME) ;
 	if(attrs->ia_valid & (HOSTFS_ATTR_ATIME | HOSTFS_ATTR_MTIME)){
 		err = stat_file(file, NULL, NULL, NULL, NULL, NULL, NULL,
 				&attrs->ia_atime, &attrs->ia_mtime, NULL,
-				NULL, NULL);
+				NULL, NULL, fd);
 		if(err != 0) return(err);
 	}
 	return(0);
-- 
1.5.1.1


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