From: Eric Biggers <ebigg...@kernel.org>
Sent: Friday, December 4, 2020 9:42 PM
> To: Konstantin Komarov <almaz.alexandrov...@paragon-software.com>
> Cc: linux-fsde...@vger.kernel.org; v...@zeniv.linux.org.uk;
> linux-kernel@vger.kernel.org; p...@kernel.org; dste...@suse.cz;
> aap...@suse.com; wi...@infradead.org; rdun...@infradead.org;
> j...@perches.com; m...@harmstone.com; nbori...@suse.com;
> linux-ntfs-...@lists.sourceforge.net; an...@tuxera.com;
> dan.carpen...@oracle.com; h...@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!
