RE: [PATCH v14 04/10] fs/ntfs3: Add file operations and implementation

[Konstantin Komarov <almaz.alexandrovich@paragon-software.com>]

Sent: Friday, December 11, 2020 7:31 PM
> To: 'Eric Biggers' <ebiggers@kernel.org>
> Cc: linux-fsdevel@vger.kernel.org; viro@zeniv.linux.org.uk; linux-kernel@vger.kernel.org; pali@kernel.org; dsterba@suse.cz;
> aaptel@suse.com; willy@infradead.org; rdunlap@infradead.org; joe@perches.com; mark@harmstone.com; nborisov@suse.com;
> linux-ntfs-dev@lists.sourceforge.net; anton@tuxera.com; dan.carpenter@oracle.com; hch@lst.de
> Subject: RE: [PATCH v14 04/10] fs/ntfs3: Add file operations and implementation
> 
> From: Eric Biggers <ebiggers@kernel.org>
> Sent: Friday, December 4, 2020 9:42 PM
> > To: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
> > Cc: linux-fsdevel@vger.kernel.org; viro@zeniv.linux.org.uk; linux-kernel@vger.kernel.org; pali@kernel.org; dsterba@suse.cz;
> > aaptel@suse.com; willy@infradead.org; rdunlap@infradead.org; joe@perches.com; mark@harmstone.com; nborisov@suse.com;
> > linux-ntfs-dev@lists.sourceforge.net; anton@tuxera.com; dan.carpenter@oracle.com; hch@lst.de
> > Subject: Re: [PATCH v14 04/10] fs/ntfs3: Add file operations and implementation
> >
> > On Fri, Dec 04, 2020 at 06:45:54PM +0300, Konstantin Komarov wrote:
> > > +/* external compression lzx/xpress */
> > > +static int decompress_lzx_xpress(struct ntfs_sb_info *sbi, const char *cmpr,
> > > +				 size_t cmpr_size, void *unc, size_t unc_size,
> > > +				 u32 frame_size)
> > > +{
> > > +	int err;
> > > +	void *ctx;
> > > +
> > > +	if (cmpr_size == unc_size) {
> > > +		/* frame not compressed */
> > > +		memcpy(unc, cmpr, unc_size);
> > > +		return 0;
> > > +	}
> > > +
> > > +	err = 0;
> > > +	ctx = NULL;
> > > +	spin_lock(&sbi->compress.lock);
> > > +	if (frame_size == 0x8000) {
> > > +		/* LZX: frame compressed */
> > > +		if (!sbi->compress.lzx) {
> > > +			/* Lazy initialize lzx decompress context */
> > > +			spin_unlock(&sbi->compress.lock);
> > > +			ctx = lzx_allocate_decompressor(0x8000);
> > > +			if (!ctx)
> > > +				return -ENOMEM;
> > > +			if (IS_ERR(ctx)) {
> > > +				/* should never failed */
> > > +				err = PTR_ERR(ctx);
> > > +				goto out;
> > > +			}
> > > +
> > > +			spin_lock(&sbi->compress.lock);
> > > +			if (!sbi->compress.lzx) {
> > > +				sbi->compress.lzx = ctx;
> > > +				ctx = NULL;
> > > +			}
> > > +		}
> > > +
> > > +		if (lzx_decompress(sbi->compress.lzx, cmpr, cmpr_size, unc,
> > > +				   unc_size)) {
> > > +			err = -EINVAL;
> > > +		}
> > > +	} else {
> > > +		/* XPRESS: frame compressed */
> > > +		if (!sbi->compress.xpress) {
> > > +			/* Lazy initialize xpress decompress context */
> > > +			spin_unlock(&sbi->compress.lock);
> > > +			ctx = xpress_allocate_decompressor();
> > > +			if (!ctx)
> > > +				return -ENOMEM;
> > > +
> > > +			spin_lock(&sbi->compress.lock);
> > > +			if (!sbi->compress.xpress) {
> > > +				sbi->compress.xpress = ctx;
> > > +				ctx = NULL;
> > > +			}
> > > +		}
> > > +
> > > +		if (xpress_decompress(sbi->compress.xpress, cmpr, cmpr_size,
> > > +				      unc, unc_size)) {
> > > +			err = -EINVAL;
> > > +		}
> > > +	}
> > > +	spin_unlock(&sbi->compress.lock);
> > > +out:
> > > +	ntfs_free(ctx);
> > > +	return err;
> > > +}
> >
> > Decompression is a somewhat heavyweight operation.  Not the type of thing that
> > should be done while holding a spin lock.
> >
> > - Eric
> 
> Hi Eric! We plan to swap spinlock to mutex in the next version.
> 
> Best regards!

Hi Eric! Changed the global spinlock to the mutexes for each type of compression.
This should resolve the problem. Please check out the V16.

Thanks!