linux-kernel - RE: [PATCH v7 1/11] fs: Add support FALLOC_FL_INSERT

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Date:	Wed, 07 Jan 2015 14:46:41 +0900
From:	Namjae Jeon <namjae.jeon@...sung.com>
To:	'Brian Foster' <bfoster@...hat.com>
Cc:	'Dave Chinner' <david@...morbit.com>,
	'Theodore Ts'o' <tytso@....edu>, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	'linux-ext4' <linux-ext4@...r.kernel.org>, xfs@....sgi.com,
	'Ashish Sangwan' <a.sangwan@...sung.com>
Subject: RE: [PATCH v7 1/11] fs: Add support FALLOC_FL_INSERT_RANGE for
 fallocate

> On Fri, Jan 02, 2015 at 06:40:33PM +0900, Namjae Jeon wrote:
> > FALLOC_FL_INSERT_RANGE command is the opposite command of
> > FALLOC_FL_COLLAPSE_RANGE that is needed for advertisers or someone who want to
> > add some data in the middle of file. FALLOC_FL_INSERT_RANGE will create space
> > for writing new data within a file after shifting extents to right as given
> > length. and this command also has same limitation as FALLOC_FL_COLLAPSE_RANGE,
> > that is block boundary and use ftruncate(2) for crosses EOF.
> >
> > Signed-off-by: Namjae Jeon <namjae.jeon@...sung.com>
> > Signed-off-by: Ashish Sangwan <a.sangwan@...sung.com>
> > ---
> >  fs/open.c                   |  8 +++++++-
> >  include/uapi/linux/falloc.h | 15 +++++++++++++++
> >  2 files changed, 22 insertions(+), 1 deletion(-)
> >
> > diff --git a/fs/open.c b/fs/open.c
> > index 36662d0..74ed498 100644
> > --- a/fs/open.c
> > +++ b/fs/open.c
> > @@ -232,7 +232,8 @@ int do_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
> >
> >  	/* Return error if mode is not supported */
> >  	if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE |
> > -		     FALLOC_FL_COLLAPSE_RANGE | FALLOC_FL_ZERO_RANGE))
> > +		     FALLOC_FL_COLLAPSE_RANGE | FALLOC_FL_ZERO_RANGE |
> > +		     FALLOC_FL_INSERT_RANGE))
> >  		return -EOPNOTSUPP;
> >
> >  	/* Punch hole and zero range are mutually exclusive */
> > @@ -250,6 +251,11 @@ int do_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
> >  	    (mode & ~FALLOC_FL_COLLAPSE_RANGE))
> >  		return -EINVAL;
> >
> > +	/* Insert range should only be used exclusively. */
> > +	if ((mode & FALLOC_FL_INSERT_RANGE) &&
> > +	    (mode & ~FALLOC_FL_INSERT_RANGE))
> > +		return -EINVAL;
> > +
> >  	if (!(file->f_mode & FMODE_WRITE))
> >  		return -EBADF;
> >
> > diff --git a/include/uapi/linux/falloc.h b/include/uapi/linux/falloc.h
> > index d1197ae..1f20723 100644
> > --- a/include/uapi/linux/falloc.h
> > +++ b/include/uapi/linux/falloc.h
> > @@ -41,4 +41,19 @@
> >   */
> >  #define FALLOC_FL_ZERO_RANGE		0x10
> >
> > +/*
> > + * FALLOC_FL_INSERT_RANGE is use to insert space within the file size without
> 
> 				used
> 
> > + * overwriting any existing data. The contents of the file beyond offset are
> > + * shifted towards right by len bytes to create a hole.  As such, this
> > + * operation will increase the size of the file by len bytes.
> 
> I suppose we should split this comment up into a few paragraphs similar
> to the collapse range comment it is based on. That means we split
> here...
> 
> > + * Different filesystems may implement different limitations on the granularity
> > + * of the operation. Most will limit operations to filesystem block size
> > + * boundaries, but this boundary may be larger or smaller depending on
> > + * the filesystem and/or the configuration of the filesystem or file.
> 
> ... and here.
> 
> Otherwise this looks fine to me.
Okay, I will fix them.
> 
> Brian
> 
> > + * Attempting to insert space using this flag at OR beyond the end of
> > + * the file is considered an illegal operation - just use ftruncate(2) or
> > + * fallocate(2) with mode 0 for such type of operations.
> > + */
> > +#define FALLOC_FL_INSERT_RANGE		0x20
> > +
> >  #endif /* _UAPI_FALLOC_H_ */
> > --
> > 1.7.11-rc0
> >

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