linux-ext4 - Re: [PATCH 2/2] libext2fs: support allocating uninit blocks in bmap2()

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Date:	Wed, 28 May 2014 12:48:06 -0700
From:	"Darrick J. Wong" <darrick.wong@...cle.com>
To:	Lukáš Czerner <lczerner@...hat.com>
Cc:	tytso@....edu, linux-ext4@...r.kernel.org
Subject: Re: [PATCH 2/2] libext2fs: support allocating uninit blocks in
 bmap2()

On Tue, May 27, 2014 at 06:28:22PM +0200, Lukáš Czerner wrote:
> On Wed, 7 May 2014, Darrick J. Wong wrote:
> 
> > Date: Wed, 7 May 2014 17:14:47 -0700
> > From: Darrick J. Wong <darrick.wong@...cle.com>
> > To: Lukáš Czerner <lczerner@...hat.com>
> > Cc: tytso@....edu, linux-ext4@...r.kernel.org
> > Subject: [PATCH 2/2] libext2fs: support allocating uninit blocks in bmap2()
> > 
> > Here's the second part, which for the most part is the old patch, but wired up
> > to use the bits in the other patch.
> 
> Looks good
> 
> Reviewed-by: Lukas Czerner <lczerner@...hat.com>
> 
> but I wonder how effective will this be with zero range when we're
> doing this on block at the time.

Not a lot, but hopefully you used ext2fs_fallocate() (and extents) if you
wanted more than one block.

--D
> 
> Thanks!
> -Lukas
> 
> > 
> > --D
> > ---
> > In order to support fallocate, we need to be able to have
> > ext2fs_bmap2() allocate blocks and put them into uninitialized
> > extents.  There's a flag to do this in the extent code, but it's not
> > exposed to the bmap2 interface, so plumb that in.  Eventually fuse2fs
> > or somebody will use it.
> > 
> > Signed-off-by: Darrick J. Wong <darrick.wong@...cle.com>
> > ---
> >  lib/ext2fs/bmap.c   |   24 ++++++++++++++++++++++--
> >  lib/ext2fs/ext2fs.h |    1 +
> >  2 files changed, 23 insertions(+), 2 deletions(-)
> > 
> > diff --git a/lib/ext2fs/bmap.c b/lib/ext2fs/bmap.c
> > index c1d0e6f..a4dc8ef 100644
> > --- a/lib/ext2fs/bmap.c
> > +++ b/lib/ext2fs/bmap.c
> > @@ -72,6 +72,11 @@ static _BMAP_INLINE_ errcode_t block_ind_bmap(ext2_filsys fs, int flags,
> >  					    block_buf + fs->blocksize, &b);
> >  		if (retval)
> >  			return retval;
> > +		if (flags & BMAP_UNINIT) {
> > +			retval = ext2fs_zero_blocks2(fs, b, 1, NULL, NULL);
> > +			if (retval)
> > +				return retval;
> > +		}
> >  
> >  #ifdef WORDS_BIGENDIAN
> >  		((blk_t *) block_buf)[nr] = ext2fs_swab32(b);
> > @@ -214,10 +219,13 @@ static errcode_t extent_bmap(ext2_filsys fs, ext2_ino_t ino,
> >  	errcode_t		retval = 0;
> >  	blk64_t			blk64 = 0;
> >  	int			alloc = 0;
> > +	int			set_flags;
> > +
> > +	set_flags = bmap_flags & BMAP_UNINIT ? EXT2_EXTENT_SET_BMAP_UNINIT : 0;
> >  
> >  	if (bmap_flags & BMAP_SET) {
> >  		retval = ext2fs_extent_set_bmap(handle, block,
> > -						*phys_blk, 0);
> > +						*phys_blk, set_flags);
> >  		return retval;
> >  	}
> >  	retval = ext2fs_extent_goto(handle, block);
> > @@ -254,7 +262,7 @@ got_block:
> >  		alloc++;
> >  	set_extent:
> >  		retval = ext2fs_extent_set_bmap(handle, block,
> > -						blk64, 0);
> > +						blk64, set_flags);
> >  		if (retval) {
> >  			ext2fs_block_alloc_stats2(fs, blk64, -1);
> >  			return retval;
> > @@ -345,6 +353,12 @@ errcode_t ext2fs_bmap2(ext2_filsys fs, ext2_ino_t ino, struct ext2_inode *inode,
> >  		goto done;
> >  	}
> >  
> > +	if ((bmap_flags & BMAP_SET) && (bmap_flags & BMAP_UNINIT)) {
> > +		retval = ext2fs_zero_blocks2(fs, *phys_blk, 1, NULL, NULL);
> > +		if (retval)
> > +			goto done;
> > +	}
> > +
> >  	if (block < EXT2_NDIR_BLOCKS) {
> >  		if (bmap_flags & BMAP_SET) {
> >  			b = *phys_blk;
> > @@ -360,6 +374,12 @@ errcode_t ext2fs_bmap2(ext2_filsys fs, ext2_ino_t ino, struct ext2_inode *inode,
> >  			retval = ext2fs_alloc_block(fs, b, block_buf, &b);
> >  			if (retval)
> >  				goto done;
> > +			if (bmap_flags & BMAP_UNINIT) {
> > +				retval = ext2fs_zero_blocks2(fs, b, 1, NULL,
> > +							     NULL);
> > +				if (retval)
> > +					goto done;
> > +			}
> >  			inode_bmap(inode, block) = b;
> >  			blocks_alloc++;
> >  			*phys_blk = b;
> > diff --git a/lib/ext2fs/ext2fs.h b/lib/ext2fs/ext2fs.h
> > index 599c972..819a14a 100644
> > --- a/lib/ext2fs/ext2fs.h
> > +++ b/lib/ext2fs/ext2fs.h
> > @@ -527,6 +527,7 @@ typedef struct ext2_icount *ext2_icount_t;
> >   */
> >  #define BMAP_ALLOC	0x0001
> >  #define BMAP_SET	0x0002
> > +#define BMAP_UNINIT	0x0004
> >  
> >  /*
> >   * Returned flags from ext2fs_bmap
> > 

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