[Cluster-devel] [PATCH] gfs2: hole_size improvement
Andreas Gruenbacher
agruenba at redhat.com
Wed Apr 11 13:37:25 UTC 2018
Hi Andy,
On 11 April 2018 at 15:00, Andrew Price <anprice at redhat.com> wrote:
> Hi Andreas,
>
> I only have a few nitpicks...
>
> On 10/04/18 18:39, Andreas Gruenbacher wrote:
>>
>> Rewrite function hole_size so that it computes the entire size of a
>> hole. Previously, the hole size returned wasn't guaranteed to span the
>> entire hole and multiple invocations of hole_size could be needed to
>> reach the next bit of data.
>>
>> Signed-off-by: Andreas Gruenbacher <agruenba at redhat.com>
>> ---
>> fs/gfs2/bmap.c | 106
>> ++++++++++++++++++++++++++++++++++++---------------------
>> 1 file changed, 67 insertions(+), 39 deletions(-)
>>
>> diff --git a/fs/gfs2/bmap.c b/fs/gfs2/bmap.c
>> index 8c25a64d8ae0..14c21825b890 100644
>> --- a/fs/gfs2/bmap.c
>> +++ b/fs/gfs2/bmap.c
>> @@ -279,6 +279,12 @@ static inline __be64 *metapointer(unsigned int
>> height, const struct metapath *mp
>> return p + mp->mp_list[height];
>> }
>> +static inline const __be64 *metaend(unsigned int height, const struct
>> metapath *mp)
>> +{
>> + const struct buffer_head *bh = mp->mp_bh[height];
>> + return (const __be64 *)(bh->b_data + bh->b_size);
>> +}
>> +
>> static void gfs2_metapath_ra(struct gfs2_glock *gl, __be64 *start,
>> __be64 *end)
>> {
>> const __be64 *t;
>> @@ -631,56 +637,78 @@ static int gfs2_iomap_alloc(struct inode *inode,
>> struct iomap *iomap,
>> * hole_size - figure out the size of a hole
>> * @inode: The inode
>> * @lblock: The logical starting block number
>> - * @mp: The metapath
>> + * @mp: The metapath at lblock
>> + * @pholesz: The hole size in bytes (output)
>> + *
>> + * This function modifies @mp.
>> *
>> - * Returns: The hole size in bytes
>> + * Returns: errno on error
>> *
>> */
>> -static u64 hole_size(struct inode *inode, sector_t lblock, struct
>> metapath *mp)
>> +static int hole_size(struct inode *inode, sector_t lblock, struct
>> metapath *mp,
>> + u64 *pholesz)
>> {
>> + sector_t lblock_end = (i_size_read(inode) + i_blocksize(inode) -
>> 1) >>
>> + inode->i_blkbits;
>> struct gfs2_inode *ip = GFS2_I(inode);
>> struct gfs2_sbd *sdp = GFS2_SB(inode);
>> - struct metapath mp_eof;
>> - u64 factor = 1;
>> - int hgt;
>> - u64 holesz = 0;
>> const __be64 *first, *end, *ptr;
>> - const struct buffer_head *bh;
>> - u64 lblock_stop = (i_size_read(inode) - 1) >> inode->i_blkbits;
>> - int zeroptrs;
>> - bool done = false;
>> -
>> - /* Get another metapath, to the very last byte */
>> - find_metapath(sdp, lblock_stop, &mp_eof, ip->i_height);
>> - for (hgt = ip->i_height - 1; hgt >= 0 && !done; hgt--) {
>> - bh = mp->mp_bh[hgt];
>> - if (bh) {
>> - zeroptrs = 0;
>> - first = metapointer(hgt, mp);
>> - end = (const __be64 *)(bh->b_data + bh->b_size);
>> -
>> - for (ptr = first; ptr < end; ptr++) {
>> - if (*ptr) {
>> - done = true;
>> - break;
>> - } else {
>> - zeroptrs++;
>> - }
>> + u64 holesz = 0, factor = 1;
>> + int hgt, ret;
>
> hgt could be unsigned for consistency and checking.
Right, it can't go negative (anymore).
>> +
>> + for (hgt = ip->i_height - 1; hgt >= mp->mp_aheight; hgt--)
>> + factor *= sdp->sd_inptrs;
>> +
>> + for (;;) {
>> + /* Count the number of zero pointers. */
>> + first = metapointer(hgt, mp);
>> + end = metaend(hgt, mp);
>> + if (end - first > lblock_end - lblock - holesz)
>> + end = first + lblock_end - lblock - holesz;
>> + for (ptr = first; ptr < end; ptr++) {
>> + if (*ptr) {
>> + holesz += (ptr - first) * factor;
>> + if (hgt == ip->i_height - 1)
>> + goto out;
>> + mp->mp_list[hgt] += (ptr - first);
>> + goto fill_up_metapath;
>> }
>> - } else {
>> - zeroptrs = sdp->sd_inptrs;
>> }
>> - if (factor * zeroptrs >= lblock_stop - lblock + 1) {
>> - holesz = lblock_stop - lblock + 1;
>> - break;
>> + holesz += (ptr - first) * factor;
>> +
>> +lower_metapath:
>> + /* Decrease height of metapath. */
>> + brelse(mp->mp_bh[hgt]);
>> + mp->mp_bh[hgt] = NULL;
>> + mp->mp_list[hgt] = 0;
>> + if (!hgt)
>> + goto out;
>> + hgt--;
>> + factor *= sdp->sd_inptrs;
>> +
>> + /* Advance in metadata tree. */
>> + (mp->mp_list[hgt])++;
>> + first = metapointer(hgt, mp);
>> + end = metaend(hgt, mp);
>> + if (first >= end) {
>> + if (!hgt)
>> + goto out;
>> + goto lower_metapath;
>> }
>> - holesz += factor * zeroptrs;
>> - factor *= sdp->sd_inptrs;
>> - if (hgt && (mp->mp_list[hgt - 1] < mp_eof.mp_list[hgt -
>> 1]))
>> - (mp->mp_list[hgt - 1])++;
>> +fill_up_metapath:
>> + /* Fill up metapath. */
>
> Comment could be removed as the function name and the label are the same as
> the comment :)
Ok.
>> + ret = fillup_metapath(ip, mp, ip->i_height - 1);
>> + if (ret < 0)
>> + return ret;
>> + while (ret--) {
>> + hgt++;
>
>
> Could be taken out of the loop as hgt += ret
>
> The flow is a little hard to follow but I don't see any obvious problems.
> Has it been tested with directories as well as files?
No, I need to think the directory case through some more. The only
"hole" in directories is at the end of the file though.
> Reviewed-by: Andrew Price <anprice at redhat.com>
>
> Andy
>
>> + factor /= sdp->sd_inptrs;
>> + }
>> }
>> - return holesz << inode->i_blkbits;
>> +out:
>> + *pholesz = holesz << inode->i_blkbits;
>> + return 0;
>> }
>> static void gfs2_stuffed_iomap(struct inode *inode, struct iomap
>> *iomap)
>> @@ -804,7 +832,7 @@ int gfs2_iomap_begin(struct inode *inode, loff_t pos,
>> loff_t length,
>> if (pos >= size)
>> ret = -ENOENT;
>> else if (height <= ip->i_height)
>> - iomap->length = hole_size(inode, lblock, &mp);
>> + ret = hole_size(inode, lblock, &mp,
>> &iomap->length);
>> else
>> iomap->length = size - pos;
>> }
Thanks,
Andreas
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