[PATCH v2 1/2] Add __do_ftruncate that truncates a struct file*

[PATCH v2 1/2] Add __do_ftruncate that truncates a struct file*

[Tony Solomonik]

do_sys_ftruncate receives a file descriptor, fgets the struct file*, and
finally actually truncates the file.

__do_ftruncate allows for truncating a file without fgets.
---
 fs/open.c                | 52 ++++++++++++++++++++++++----------------
 include/linux/syscalls.h |  2 ++
 2 files changed, 33 insertions(+), 21 deletions(-)

diff --git a/fs/open.c b/fs/open.c
index 02dc608d40d8..b32ac430666c 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -154,47 +154,57 @@ COMPAT_SYSCALL_DEFINE2(truncate, const char __user *, path, compat_off_t, length
 }
 #endif
 
-long do_sys_ftruncate(unsigned int fd, loff_t length, int small)
+long __do_ftruncate(struct file *file, loff_t length, int small)
 {
 	struct inode *inode;
 	struct dentry *dentry;
-	struct fd f;
 	int error;
 
-	error = -EINVAL;
-	if (length < 0)
-		goto out;
-	error = -EBADF;
-	f = fdget(fd);
-	if (!f.file)
-		goto out;
-
 	/* explicitly opened as large or we are on 64-bit box */
-	if (f.file->f_flags & O_LARGEFILE)
+	if (file->f_flags & O_LARGEFILE)
 		small = 0;
 
-	dentry = f.file->f_path.dentry;
+	dentry = file->f_path.dentry;
 	inode = dentry->d_inode;
 	error = -EINVAL;
-	if (!S_ISREG(inode->i_mode) || !(f.file->f_mode & FMODE_WRITE))
-		goto out_putf;
+	if (!S_ISREG(inode->i_mode) || !(file->f_mode & FMODE_WRITE))
+		goto out;
 
 	error = -EINVAL;
 	/* Cannot ftruncate over 2^31 bytes without large file support */
 	if (small && length > MAX_NON_LFS)
-		goto out_putf;
+		goto out;
 
 	error = -EPERM;
 	/* Check IS_APPEND on real upper inode */
-	if (IS_APPEND(file_inode(f.file)))
-		goto out_putf;
+	if (IS_APPEND(file_inode(file)))
+		goto out;
 	sb_start_write(inode->i_sb);
-	error = security_file_truncate(f.file);
+	error = security_file_truncate(file);
 	if (!error)
-		error = do_truncate(file_mnt_idmap(f.file), dentry, length,
-				    ATTR_MTIME | ATTR_CTIME, f.file);
+		error = do_truncate(file_mnt_idmap(file), dentry, length,
+				    ATTR_MTIME | ATTR_CTIME, file);
 	sb_end_write(inode->i_sb);
-out_putf:
+
+out:
+  return error;
+}
+
+long do_sys_ftruncate(unsigned int fd, loff_t length, int small)
+{
+	struct fd f;
+	int error;
+
+	error = -EINVAL;
+	if (length < 0)
+		goto out;
+	error = -EBADF;
+	f = fdget(fd);
+	if (!f.file)
+		goto out;
+
+	error = __do_ftruncate(f.file, length, small);
+
 	fdput(f);
 out:
 	return error;
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index fd9d12de7e92..e8c56986e751 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -1229,6 +1229,8 @@ static inline long ksys_lchown(const char __user *filename, uid_t user,
 			     AT_SYMLINK_NOFOLLOW);
 }
 
+extern long __do_ftruncate(struct file *file, loff_t length, int small);
+
 extern long do_sys_ftruncate(unsigned int fd, loff_t length, int small);
 
 static inline long ksys_ftruncate(unsigned int fd, loff_t length)
-- 
2.34.1

[PATCH v2 2/2] io_uring: add support for ftruncate

[Tony Solomonik]

Libraries that are built on io_uring currently need to maintain a
separate thread pool implementation when they want to truncate a file.
---
 include/uapi/linux/io_uring.h |  1 +
 io_uring/Makefile             |  2 +-
 io_uring/opdef.c              |  9 +++++++
 io_uring/truncate.c           | 47 +++++++++++++++++++++++++++++++++++
 io_uring/truncate.h           |  4 +++
 5 files changed, 62 insertions(+), 1 deletion(-)
 create mode 100644 io_uring/truncate.c
 create mode 100644 io_uring/truncate.h

diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index f1c16f817742..be682e000c94 100644
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -253,6 +253,7 @@ enum io_uring_op {
 	IORING_OP_FUTEX_WAIT,
 	IORING_OP_FUTEX_WAKE,
 	IORING_OP_FUTEX_WAITV,
+	IORING_OP_FTRUNCATE,
 
 	/* this goes last, obviously */
 	IORING_OP_LAST,
diff --git a/io_uring/Makefile b/io_uring/Makefile
index e5be47e4fc3b..4f8ed6530a29 100644
--- a/io_uring/Makefile
+++ b/io_uring/Makefile
@@ -8,6 +8,6 @@ obj-$(CONFIG_IO_URING)		+= io_uring.o xattr.o nop.o fs.o splice.o \
 					statx.o net.o msg_ring.o timeout.o \
 					sqpoll.o fdinfo.o tctx.o poll.o \
 					cancel.o kbuf.o rsrc.o rw.o opdef.o \
-					notif.o waitid.o
+					notif.o waitid.o truncate.o
 obj-$(CONFIG_IO_WQ)		+= io-wq.o
 obj-$(CONFIG_FUTEX)		+= futex.o
diff --git a/io_uring/opdef.c b/io_uring/opdef.c
index 799db44283c7..7830d087d03f 100644
--- a/io_uring/opdef.c
+++ b/io_uring/opdef.c
@@ -35,6 +35,7 @@
 #include "rw.h"
 #include "waitid.h"
 #include "futex.h"
+#include "truncate.h"
 
 static int io_no_issue(struct io_kiocb *req, unsigned int issue_flags)
 {
@@ -469,6 +470,11 @@ const struct io_issue_def io_issue_defs[] = {
 		.prep			= io_eopnotsupp_prep,
 #endif
 	},
+	[IORING_OP_FTRUNCATE] = {
+		.needs_file		= 1,
+		.prep			= io_ftruncate_prep,
+		.issue			= io_ftruncate,
+	},
 };
 
 const struct io_cold_def io_cold_defs[] = {
@@ -704,6 +710,9 @@ const struct io_cold_def io_cold_defs[] = {
 	[IORING_OP_FUTEX_WAITV] = {
 		.name			= "FUTEX_WAITV",
 	},
+	[IORING_OP_FTRUNCATE] = {
+		.name			= "FTRUNCATE",
+	},
 };
 
 const char *io_uring_get_opcode(u8 opcode)
diff --git a/io_uring/truncate.c b/io_uring/truncate.c
new file mode 100644
index 000000000000..9d160b91949c
--- /dev/null
+++ b/io_uring/truncate.c
@@ -0,0 +1,47 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/fs.h>
+#include <linux/file.h>
+#include <linux/mm.h>
+#include <linux/slab.h>
+#include <linux/syscalls.h>
+#include <linux/io_uring.h>
+
+#include <uapi/linux/io_uring.h>
+
+#include "../fs/internal.h"
+
+#include "io_uring.h"
+#include "truncate.h"
+
+struct io_ftrunc {
+	struct file			*file;
+	loff_t				len;
+};
+
+int io_ftruncate_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
+{
+	struct io_ftrunc *ft = io_kiocb_to_cmd(req, struct io_ftrunc);
+
+	if (sqe->addr || sqe->rw_flags || sqe->buf_index || sqe->splice_fd_in)
+		return -EINVAL;
+
+	ft->len = READ_ONCE(sqe->off);
+
+	req->flags |= REQ_F_FORCE_ASYNC;
+	return 0;
+}
+
+int io_ftruncate(struct io_kiocb *req, unsigned int issue_flags)
+{
+	struct io_ftrunc *ft = io_kiocb_to_cmd(req, struct io_ftrunc);
+	int ret;
+
+	WARN_ON_ONCE(issue_flags & IO_URING_F_NONBLOCK);
+
+	ret = __do_ftruncate(req->file, ft->len, 1);
+
+	io_req_set_res(req, ret, 0);
+	return IOU_OK;
+}
diff --git a/io_uring/truncate.h b/io_uring/truncate.h
new file mode 100644
index 000000000000..ec088293a478
--- /dev/null
+++ b/io_uring/truncate.h
@@ -0,0 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0
+
+int io_ftruncate_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe);
+int io_ftruncate(struct io_kiocb *req, unsigned int issue_flags);
-- 
2.34.1

[PATCH v2 1/2] Add __do_ftruncate that truncates a struct file*

[Tony Solomonik]

do_sys_ftruncate receives a file descriptor, fgets the struct file*, and
finally actually truncates the file.

__do_ftruncate allows for truncating a file without fgets.
---
 fs/open.c                | 52 ++++++++++++++++++++++++----------------
 include/linux/syscalls.h |  2 ++
 2 files changed, 33 insertions(+), 21 deletions(-)

diff --git a/fs/open.c b/fs/open.c
index 02dc608d40d8..b32ac430666c 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -154,47 +154,57 @@ COMPAT_SYSCALL_DEFINE2(truncate, const char __user *, path, compat_off_t, length
 }
 #endif
 
-long do_sys_ftruncate(unsigned int fd, loff_t length, int small)
+long __do_ftruncate(struct file *file, loff_t length, int small)
 {
 	struct inode *inode;
 	struct dentry *dentry;
-	struct fd f;
 	int error;
 
-	error = -EINVAL;
-	if (length < 0)
-		goto out;
-	error = -EBADF;
-	f = fdget(fd);
-	if (!f.file)
-		goto out;
-
 	/* explicitly opened as large or we are on 64-bit box */
-	if (f.file->f_flags & O_LARGEFILE)
+	if (file->f_flags & O_LARGEFILE)
 		small = 0;
 
-	dentry = f.file->f_path.dentry;
+	dentry = file->f_path.dentry;
 	inode = dentry->d_inode;
 	error = -EINVAL;
-	if (!S_ISREG(inode->i_mode) || !(f.file->f_mode & FMODE_WRITE))
-		goto out_putf;
+	if (!S_ISREG(inode->i_mode) || !(file->f_mode & FMODE_WRITE))
+		goto out;
 
 	error = -EINVAL;
 	/* Cannot ftruncate over 2^31 bytes without large file support */
 	if (small && length > MAX_NON_LFS)
-		goto out_putf;
+		goto out;
 
 	error = -EPERM;
 	/* Check IS_APPEND on real upper inode */
-	if (IS_APPEND(file_inode(f.file)))
-		goto out_putf;
+	if (IS_APPEND(file_inode(file)))
+		goto out;
 	sb_start_write(inode->i_sb);
-	error = security_file_truncate(f.file);
+	error = security_file_truncate(file);
 	if (!error)
-		error = do_truncate(file_mnt_idmap(f.file), dentry, length,
-				    ATTR_MTIME | ATTR_CTIME, f.file);
+		error = do_truncate(file_mnt_idmap(file), dentry, length,
+				    ATTR_MTIME | ATTR_CTIME, file);
 	sb_end_write(inode->i_sb);
-out_putf:
+
+out:
+  return error;
+}
+
+long do_sys_ftruncate(unsigned int fd, loff_t length, int small)
+{
+	struct fd f;
+	int error;
+
+	error = -EINVAL;
+	if (length < 0)
+		goto out;
+	error = -EBADF;
+	f = fdget(fd);
+	if (!f.file)
+		goto out;
+
+	error = __do_ftruncate(f.file, length, small);
+
 	fdput(f);
 out:
 	return error;
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index fd9d12de7e92..e8c56986e751 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -1229,6 +1229,8 @@ static inline long ksys_lchown(const char __user *filename, uid_t user,
 			     AT_SYMLINK_NOFOLLOW);
 }
 
+extern long __do_ftruncate(struct file *file, loff_t length, int small);
+
 extern long do_sys_ftruncate(unsigned int fd, loff_t length, int small);
 
 static inline long ksys_ftruncate(unsigned int fd, loff_t length)
-- 
2.34.1

Re: [PATCH v2 1/2] Add __do_ftruncate that truncates a struct file*

[Gabriel Krisman Bertazi]

Tony Solomonik <tony.solomonik@gmail.com> writes:

> do_sys_ftruncate receives a file descriptor, fgets the struct file*, and
> finally actually truncates the file.

This need to be Cc'ed to the VFS maintainers and appropriated lists.
Also, you need a signed-off-by line and cover letter.

Take a look at:

https://www.kernel.org/doc/html/v6.7/process/submitting-patches.html

>
> __do_ftruncate allows for truncating a file without fgets.
> ---
>  fs/open.c                | 52 ++++++++++++++++++++++++----------------
>  include/linux/syscalls.h |  2 ++
>  2 files changed, 33 insertions(+), 21 deletions(-)
>
> diff --git a/fs/open.c b/fs/open.c
> index 02dc608d40d8..b32ac430666c 100644
> --- a/fs/open.c
> +++ b/fs/open.c
> @@ -154,47 +154,57 @@ COMPAT_SYSCALL_DEFINE2(truncate, const char __user *, path, compat_off_t, length
>  }
>  #endif
>  
> -long do_sys_ftruncate(unsigned int fd, loff_t length, int small)
> +long __do_ftruncate(struct file *file, loff_t length, int small)
>  {
>  	struct inode *inode;
>  	struct dentry *dentry;
> -	struct fd f;
>  	int error;
>  
> -	error = -EINVAL;
> -	if (length < 0)
> -		goto out;
> -	error = -EBADF;
> -	f = fdget(fd);
> -	if (!f.file)
> -		goto out;
> -
>  	/* explicitly opened as large or we are on 64-bit box */
> -	if (f.file->f_flags & O_LARGEFILE)
> +	if (file->f_flags & O_LARGEFILE)
>  		small = 0;
>  
> -	dentry = f.file->f_path.dentry;
> +	dentry = file->f_path.dentry;
>  	inode = dentry->d_inode;
>  	error = -EINVAL;
> -	if (!S_ISREG(inode->i_mode) || !(f.file->f_mode & FMODE_WRITE))
> -		goto out_putf;
> +	if (!S_ISREG(inode->i_mode) || !(file->f_mode & FMODE_WRITE))
> +		goto out;

Just return directly here. No point in jumping to 'out' just to return
immediately.

>  
>  	error = -EINVAL;
>  	/* Cannot ftruncate over 2^31 bytes without large file support */
>  	if (small && length > MAX_NON_LFS)
> -		goto out_putf;
> +		goto out;

likewise for the others..

>  
>  	error = -EPERM;
>  	/* Check IS_APPEND on real upper inode */
> -	if (IS_APPEND(file_inode(f.file)))
> -		goto out_putf;
> +	if (IS_APPEND(file_inode(file)))
> +		goto out;
>  	sb_start_write(inode->i_sb);
> -	error = security_file_truncate(f.file);
> +	error = security_file_truncate(file);
>  	if (!error)
> -		error = do_truncate(file_mnt_idmap(f.file), dentry, length,
> -				    ATTR_MTIME | ATTR_CTIME, f.file);
> +		error = do_truncate(file_mnt_idmap(file), dentry, length,
> +				    ATTR_MTIME | ATTR_CTIME, file);
>  	sb_end_write(inode->i_sb);
> -out_putf:
> +
> +out:
> +  return error;
> +}
> +
> +long do_sys_ftruncate(unsigned int fd, loff_t length, int small)
> +{
> +	struct fd f;
> +	int error;
> +
> +	error = -EINVAL;
> +	if (length < 0)
> +		goto out;
> +	error = -EBADF;
> +	f = fdget(fd);
> +	if (!f.file)
> +		goto out;
> +
> +	error = __do_ftruncate(f.file, length, small);
> +
>  	fdput(f);
>  out:
>  	return error;

Same here.

> diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
> index fd9d12de7e92..e8c56986e751 100644
> --- a/include/linux/syscalls.h
> +++ b/include/linux/syscalls.h
> @@ -1229,6 +1229,8 @@ static inline long ksys_lchown(const char __user *filename, uid_t user,
>  			     AT_SYMLINK_NOFOLLOW);
>  }
>  
> +extern long __do_ftruncate(struct file *file, loff_t length, int small);
> +
>  extern long do_sys_ftruncate(unsigned int fd, loff_t length, int small);
>  
>  static inline long ksys_ftruncate(unsigned int fd, loff_t length)

-- 
Gabriel Krisman Bertazi

Re: [PATCH v2 1/2] Add __do_ftruncate that truncates a struct file*

[Jens Axboe]

On 1/23/24 4:33 AM, Tony Solomonik wrote:
> do_sys_ftruncate receives a file descriptor, fgets the struct file*, and
> finally actually truncates the file.
> 
> __do_ftruncate allows for truncating a file without fgets.
> ---
>  fs/open.c                | 52 ++++++++++++++++++++++++----------------
>  include/linux/syscalls.h |  2 ++
>  2 files changed, 33 insertions(+), 21 deletions(-)
> 
> diff --git a/fs/open.c b/fs/open.c
> index 02dc608d40d8..b32ac430666c 100644
> --- a/fs/open.c
> +++ b/fs/open.c
> @@ -154,47 +154,57 @@ COMPAT_SYSCALL_DEFINE2(truncate, const char __user *, path, compat_off_t, length
>  }
>  #endif
>  
> -long do_sys_ftruncate(unsigned int fd, loff_t length, int small)
> +long __do_ftruncate(struct file *file, loff_t length, int small)
>  {
>  	struct inode *inode;
>  	struct dentry *dentry;
> -	struct fd f;
>  	int error;
>  
> -	error = -EINVAL;
> -	if (length < 0)
> -		goto out;
> -	error = -EBADF;
> -	f = fdget(fd);
> -	if (!f.file)
> -		goto out;
> -
>  	/* explicitly opened as large or we are on 64-bit box */
> -	if (f.file->f_flags & O_LARGEFILE)
> +	if (file->f_flags & O_LARGEFILE)
>  		small = 0;
>  
> -	dentry = f.file->f_path.dentry;
> +	dentry = file->f_path.dentry;
>  	inode = dentry->d_inode;
>  	error = -EINVAL;
> -	if (!S_ISREG(inode->i_mode) || !(f.file->f_mode & FMODE_WRITE))
> -		goto out_putf;
> +	if (!S_ISREG(inode->i_mode) || !(file->f_mode & FMODE_WRITE))
> +		goto out;
>  
>  	error = -EINVAL;
>  	/* Cannot ftruncate over 2^31 bytes without large file support */
>  	if (small && length > MAX_NON_LFS)
> -		goto out_putf;
> +		goto out;
>  
>  	error = -EPERM;
>  	/* Check IS_APPEND on real upper inode */
> -	if (IS_APPEND(file_inode(f.file)))
> -		goto out_putf;
> +	if (IS_APPEND(file_inode(file)))
> +		goto out;
>  	sb_start_write(inode->i_sb);
> -	error = security_file_truncate(f.file);
> +	error = security_file_truncate(file);
>  	if (!error)
> -		error = do_truncate(file_mnt_idmap(f.file), dentry, length,
> -				    ATTR_MTIME | ATTR_CTIME, f.file);
> +		error = do_truncate(file_mnt_idmap(file), dentry, length,
> +				    ATTR_MTIME | ATTR_CTIME, file);
>  	sb_end_write(inode->i_sb);
> -out_putf:
> +
> +out:
> +  return error;
> +}
> +
> +long do_sys_ftruncate(unsigned int fd, loff_t length, int small)
> +{
> +	struct fd f;
> +	int error;
> +
> +	error = -EINVAL;
> +	if (length < 0)
> +		goto out;
> +	error = -EBADF;
> +	f = fdget(fd);
> +	if (!f.file)
> +		goto out;
> +
> +	error = __do_ftruncate(f.file, length, small);
> +
>  	fdput(f);
>  out:

Same comments as Gabriel for the out label, just return error.

> diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
> index fd9d12de7e92..e8c56986e751 100644
> --- a/include/linux/syscalls.h
> +++ b/include/linux/syscalls.h
> @@ -1229,6 +1229,8 @@ static inline long ksys_lchown(const char __user *filename, uid_t user,
>  			     AT_SYMLINK_NOFOLLOW);
>  }
>  
> +extern long __do_ftruncate(struct file *file, loff_t length, int small);
> +
>  extern long do_sys_ftruncate(unsigned int fd, loff_t length, int small);
>  
>  static inline long ksys_ftruncate(unsigned int fd, loff_t length)

This should go in fs/internal.h, it's not a syscall related thing.

-- 
Jens Axboe

Re: [PATCH v2 1/2] Add __do_ftruncate that truncates a struct file*

[Jens Axboe]

On 1/23/24 8:38 AM, Jens Axboe wrote:
>> diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
>> index fd9d12de7e92..e8c56986e751 100644
>> --- a/include/linux/syscalls.h
>> +++ b/include/linux/syscalls.h
>> @@ -1229,6 +1229,8 @@ static inline long ksys_lchown(const char __user *filename, uid_t user,
>>  			     AT_SYMLINK_NOFOLLOW);
>>  }
>>  
>> +extern long __do_ftruncate(struct file *file, loff_t length, int small);
>> +
>>  extern long do_sys_ftruncate(unsigned int fd, loff_t length, int small);
>>  
>>  static inline long ksys_ftruncate(unsigned int fd, loff_t length)
> 
> This should go in fs/internal.h, it's not a syscall related thing.

And while at it, let's call it ftruncate_file() as that more accurately
describes what it does.

-- 
Jens Axboe