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authorJens Axboe <jens.axboe@oracle.com>2009-02-23 03:03:10 -0500
committerJens Axboe <jens.axboe@oracle.com>2009-02-26 04:45:48 -0500
commit1e42807918d17e8c93bf14fbb74be84b141334c1 (patch)
tree55b15f0f6b2c666efeb938d064f24fdd268faf40 /block/blk-merge.c
parent5e4c91c84b194b26cf592779e451f4b5be777cba (diff)
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>
Diffstat (limited to 'block/blk-merge.c')
-rw-r--r--block/blk-merge.c94
1 files changed, 53 insertions, 41 deletions
diff --git a/block/blk-merge.c b/block/blk-merge.c
index b92f5b0866b0..a104593e70c3 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -38,72 +38,84 @@ void blk_recalc_rq_sectors(struct request *rq, int nsect)
38 } 38 }
39} 39}
40 40
41void blk_recalc_rq_segments(struct request *rq) 41static unsigned int __blk_recalc_rq_segments(struct request_queue *q,
42 struct bio *bio,
43 unsigned int *seg_size_ptr)
42{ 44{
43 int nr_phys_segs;
44 unsigned int phys_size; 45 unsigned int phys_size;
45 struct bio_vec *bv, *bvprv = NULL; 46 struct bio_vec *bv, *bvprv = NULL;
46 int seg_size; 47 int cluster, i, high, highprv = 1;
47 int cluster; 48 unsigned int seg_size, nr_phys_segs;
48 struct req_iterator iter; 49 struct bio *fbio;
49 int high, highprv = 1;
50 struct request_queue *q = rq->q;
51 50
52 if (!rq->bio) 51 if (!bio)
53 return; 52 return 0;
54 53
54 fbio = bio;
55 cluster = test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags); 55 cluster = test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags);
56 seg_size = 0; 56 seg_size = 0;
57 phys_size = nr_phys_segs = 0; 57 phys_size = nr_phys_segs = 0;
58 rq_for_each_segment(bv, rq, iter) { 58 for_each_bio(bio) {
59 /* 59 bio_for_each_segment(bv, bio, i) {
60 * the trick here is making sure that a high page is never 60 /*
61 * considered part of another segment, since that might 61 * the trick here is making sure that a high page is
62 * change with the bounce page. 62 * never considered part of another segment, since that
63 */ 63 * might change with the bounce page.
64 high = page_to_pfn(bv->bv_page) > q->bounce_pfn; 64 */
65 if (high || highprv) 65 high = page_to_pfn(bv->bv_page) > q->bounce_pfn;
66 goto new_segment; 66 if (high || highprv)
67 if (cluster) {
68 if (seg_size + bv->bv_len > q->max_segment_size)
69 goto new_segment;
70 if (!BIOVEC_PHYS_MERGEABLE(bvprv, bv))
71 goto new_segment;
72 if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bv))
73 goto new_segment; 67 goto new_segment;
68 if (cluster) {
69 if (seg_size + bv->bv_len > q->max_segment_size)
70 goto new_segment;
71 if (!BIOVEC_PHYS_MERGEABLE(bvprv, bv))
72 goto new_segment;
73 if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bv))
74 goto new_segment;
75
76 seg_size += bv->bv_len;
77 bvprv = bv;
78 continue;
79 }
80new_segment:
81 if (nr_phys_segs == 1 && seg_size >
82 fbio->bi_seg_front_size)
83 fbio->bi_seg_front_size = seg_size;
74 84
75 seg_size += bv->bv_len; 85 nr_phys_segs++;
76 bvprv = bv; 86 bvprv = bv;
77 continue; 87 seg_size = bv->bv_len;
88 highprv = high;
78 } 89 }
79new_segment:
80 if (nr_phys_segs == 1 && seg_size > rq->bio->bi_seg_front_size)
81 rq->bio->bi_seg_front_size = seg_size;
82
83 nr_phys_segs++;
84 bvprv = bv;
85 seg_size = bv->bv_len;
86 highprv = high;
87 } 90 }
88 91
89 if (nr_phys_segs == 1 && seg_size > rq->bio->bi_seg_front_size) 92 if (seg_size_ptr)
93 *seg_size_ptr = seg_size;
94
95 return nr_phys_segs;
96}
97
98void blk_recalc_rq_segments(struct request *rq)
99{
100 unsigned int seg_size = 0, phys_segs;
101
102 phys_segs = __blk_recalc_rq_segments(rq->q, rq->bio, &seg_size);
103
104 if (phys_segs == 1 && seg_size > rq->bio->bi_seg_front_size)
90 rq->bio->bi_seg_front_size = seg_size; 105 rq->bio->bi_seg_front_size = seg_size;
91 if (seg_size > rq->biotail->bi_seg_back_size) 106 if (seg_size > rq->biotail->bi_seg_back_size)
92 rq->biotail->bi_seg_back_size = seg_size; 107 rq->biotail->bi_seg_back_size = seg_size;
93 108
94 rq->nr_phys_segments = nr_phys_segs; 109 rq->nr_phys_segments = phys_segs;
95} 110}
96 111
97void blk_recount_segments(struct request_queue *q, struct bio *bio) 112void blk_recount_segments(struct request_queue *q, struct bio *bio)
98{ 113{
99 struct request rq;
100 struct bio *nxt = bio->bi_next; 114 struct bio *nxt = bio->bi_next;
101 rq.q = q; 115
102 rq.bio = rq.biotail = bio;
103 bio->bi_next = NULL; 116 bio->bi_next = NULL;
104 blk_recalc_rq_segments(&rq); 117 bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio, NULL);
105 bio->bi_next = nxt; 118 bio->bi_next = nxt;
106 bio->bi_phys_segments = rq.nr_phys_segments;
107 bio->bi_flags |= (1 << BIO_SEG_VALID); 119 bio->bi_flags |= (1 << BIO_SEG_VALID);
108} 120}
109EXPORT_SYMBOL(blk_recount_segments); 121EXPORT_SYMBOL(blk_recount_segments);