block: reduce stack footprint of blk_recount_segments()
blk_recalc_rq_segments() requires a request structure passed in, which we don't have from blk_recount_segments(). So the latter allocates one on the stack, using > 400 bytes of stack for that. This can cause us to spill over one page of stack from ext4 at least: 0) 4560 400 blk_recount_segments+0x43/0x62 1) 4160 32 bio_phys_segments+0x1c/0x24 2) 4128 32 blk_rq_bio_prep+0x2a/0xf9 3) 4096 32 init_request_from_bio+0xf9/0xfe 4) 4064 112 __make_request+0x33c/0x3f6 5) 3952 144 generic_make_request+0x2d1/0x321 6) 3808 64 submit_bio+0xb9/0xc3 7) 3744 48 submit_bh+0xea/0x10e 8) 3696 368 ext4_mb_init_cache+0x257/0xa6a [ext4] 9) 3328 288 ext4_mb_regular_allocator+0x421/0xcd9 [ext4] 10) 3040 160 ext4_mb_new_blocks+0x211/0x4b4 [ext4] 11) 2880 336 ext4_ext_get_blocks+0xb61/0xd45 [ext4] 12) 2544 96 ext4_get_blocks_wrap+0xf2/0x200 [ext4] 13) 2448 80 ext4_da_get_block_write+0x6e/0x16b [ext4] 14) 2368 352 mpage_da_map_blocks+0x7e/0x4b3 [ext4] 15) 2016 352 ext4_da_writepages+0x2ce/0x43c [ext4] 16) 1664 32 do_writepages+0x2d/0x3c 17) 1632 144 __writeback_single_inode+0x162/0x2cd 18) 1488 96 generic_sync_sb_inodes+0x1e3/0x32b 19) 1392 16 sync_sb_inodes+0xe/0x10 20) 1376 48 writeback_inodes+0x69/0xb3 21) 1328 208 balance_dirty_pages_ratelimited_nr+0x187/0x2f9 22) 1120 224 generic_file_buffered_write+0x1d4/0x2c4 23) 896 176 __generic_file_aio_write_nolock+0x35f/0x393 24) 720 80 generic_file_aio_write+0x6c/0xc8 25) 640 80 ext4_file_write+0xa9/0x137 [ext4] 26) 560 320 do_sync_write+0xf0/0x137 27) 240 48 vfs_write+0xb3/0x13c 28) 192 64 sys_write+0x4c/0x74 29) 128 128 system_call_fastpath+0x16/0x1b Split the segment counting out into a __blk_recalc_rq_segments() helper to avoid allocating an onstack request just for checking the physical segment count. Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
This commit is contained in:
Jens Axboe
Родитель
5e4c91c84b
Коммит
1e42807918
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@ -38,72 +38,84 @@ void blk_recalc_rq_sectors(struct request *rq, int nsect)
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}
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}
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void blk_recalc_rq_segments(struct request *rq)
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static unsigned int __blk_recalc_rq_segments(struct request_queue *q,
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struct bio *bio,
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unsigned int *seg_size_ptr)
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{
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int nr_phys_segs;
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unsigned int phys_size;
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struct bio_vec *bv, *bvprv = NULL;
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int seg_size;
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int cluster;
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struct req_iterator iter;
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int high, highprv = 1;
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struct request_queue *q = rq->q;
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int cluster, i, high, highprv = 1;
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unsigned int seg_size, nr_phys_segs;
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struct bio *fbio;
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if (!rq->bio)
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return;
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if (!bio)
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return 0;
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fbio = bio;
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cluster = test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags);
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seg_size = 0;
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phys_size = nr_phys_segs = 0;
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rq_for_each_segment(bv, rq, iter) {
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/*
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* the trick here is making sure that a high page is never
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* considered part of another segment, since that might
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* change with the bounce page.
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*/
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high = page_to_pfn(bv->bv_page) > q->bounce_pfn;
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if (high || highprv)
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goto new_segment;
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if (cluster) {
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if (seg_size + bv->bv_len > q->max_segment_size)
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goto new_segment;
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if (!BIOVEC_PHYS_MERGEABLE(bvprv, bv))
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goto new_segment;
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if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bv))
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for_each_bio(bio) {
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bio_for_each_segment(bv, bio, i) {
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/*
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* the trick here is making sure that a high page is
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* never considered part of another segment, since that
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* might change with the bounce page.
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*/
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high = page_to_pfn(bv->bv_page) > q->bounce_pfn;
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if (high || highprv)
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goto new_segment;
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if (cluster) {
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if (seg_size + bv->bv_len > q->max_segment_size)
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goto new_segment;
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if (!BIOVEC_PHYS_MERGEABLE(bvprv, bv))
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goto new_segment;
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if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bv))
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goto new_segment;
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seg_size += bv->bv_len;
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bvprv = bv;
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continue;
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}
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seg_size += bv->bv_len;
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bvprv = bv;
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continue;
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}
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new_segment:
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if (nr_phys_segs == 1 && seg_size > rq->bio->bi_seg_front_size)
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rq->bio->bi_seg_front_size = seg_size;
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if (nr_phys_segs == 1 && seg_size >
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fbio->bi_seg_front_size)
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fbio->bi_seg_front_size = seg_size;
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nr_phys_segs++;
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bvprv = bv;
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seg_size = bv->bv_len;
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highprv = high;
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nr_phys_segs++;
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bvprv = bv;
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seg_size = bv->bv_len;
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highprv = high;
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}
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}
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if (nr_phys_segs == 1 && seg_size > rq->bio->bi_seg_front_size)
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if (seg_size_ptr)
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*seg_size_ptr = seg_size;
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return nr_phys_segs;
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}
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void blk_recalc_rq_segments(struct request *rq)
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{
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unsigned int seg_size = 0, phys_segs;
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phys_segs = __blk_recalc_rq_segments(rq->q, rq->bio, &seg_size);
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if (phys_segs == 1 && seg_size > rq->bio->bi_seg_front_size)
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rq->bio->bi_seg_front_size = seg_size;
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if (seg_size > rq->biotail->bi_seg_back_size)
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rq->biotail->bi_seg_back_size = seg_size;
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rq->nr_phys_segments = nr_phys_segs;
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rq->nr_phys_segments = phys_segs;
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}
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void blk_recount_segments(struct request_queue *q, struct bio *bio)
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{
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struct request rq;
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struct bio *nxt = bio->bi_next;
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rq.q = q;
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rq.bio = rq.biotail = bio;
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bio->bi_next = NULL;
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blk_recalc_rq_segments(&rq);
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bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio, NULL);
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bio->bi_next = nxt;
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bio->bi_phys_segments = rq.nr_phys_segments;
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bio->bi_flags |= (1 << BIO_SEG_VALID);
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}
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EXPORT_SYMBOL(blk_recount_segments);
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@ -708,6 +708,8 @@ struct req_iterator {
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};
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/* This should not be used directly - use rq_for_each_segment */
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#define for_each_bio(_bio) \
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for (; _bio; _bio = _bio->bi_next)
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#define __rq_for_each_bio(_bio, rq) \
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if ((rq->bio)) \
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for (_bio = (rq)->bio; _bio; _bio = _bio->bi_next)
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