Hello Minchan, On (11/07/14 13:55), Minchan Kim wrote: > On Thu, Nov 06, 2014 at 10:43:42PM +0900, Sergey Senozhatsky wrote: > > Hello, > > > > On (11/05/14 09:10), Minchan Kim wrote: > > > zram_rw_page returns error code to upper layer with PG_error flag > > > of the page but it should be wrong usage. If submitted IO is > > > hard fail(ie, I/O again will not succeed), we should return 0, > > > indicating that the submission was successful but the IO operation > > > failed. > > > > > > http://marc.info/?l=linux-mm&m=141511693112734&w=2 > > > > > > > well, `don't return error in case of an error' is a bit misleading. > > Yes, it was. It would be better to make it with "boolean" > and return true if sumission was successful. Anyway, it's not out of > the patch. > > > > > apart from zram there seems to be one block driver that does the > > same: brd.c [git grep page_endio]. so I Cc Nick Piggin. > > > > > This patch fixes below BUG. > > > > > > [ 179.987592] zram0: detected capacity change from 2147483648 to 0 > > > [ 179.987570] page:ffffea00008d6300 count:2 mapcount:0 mapping:ffff880025348e88 index:0x0 > > > [ 179.987570] flags: 0x100000000020002(error|mappedtodisk) > > > [ 179.987570] page dumped because: VM_BUG_ON_PAGE(!PageLocked(page)) > > > [ 179.987570] ------------[ cut here ]------------ > > > [ 179.987570] kernel BUG at mm/filemap.c:747! > > > [ 179.987570] invalid opcode: 0000 [#1] SMP > > > [ 179.987570] Dumping ftrace buffer: > > > [ 179.987570] (ftrace buffer empty) > > > [ 179.987570] Modules linked in: > > > [ 179.987570] CPU: 10 PID: 23080 Comm: udisks-part-id Not tainted 3.18.0-rc2+ #584 > > > [ 179.987570] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 > > > [ 179.987570] task: ffff88001de74200 ti: ffff88001b220000 task.ti: ffff88001b220000 > > > [ 179.987570] RIP: 0010:[<ffffffff8114ae12>] [<ffffffff8114ae12>] unlock_page+0x82/0x90 > > > [ 179.987570] RSP: 0018:ffff88001b223998 EFLAGS: 00010246 > > > [ 179.987570] RAX: 0000000000000036 RBX: ffff88001e009a50 RCX: 000000000910090f > > > [ 179.987570] RDX: 0000000000000910 RSI: 0000000000000001 RDI: ffffffff81600a7f > > > [ 179.987570] RBP: ffff88001b223998 R08: 0000000000000001 R09: 0000000000000001 > > > [ 179.987570] R10: 0000000000000001 R11: 0000000000000000 R12: 0000000000000001 > > > [ 179.987570] R13: ffff88001e0099c0 R14: 00000000fffffffb R15: ffff88001e0099c0 > > > [ 179.987570] FS: 00007fcb17c73800(0000) GS:ffff880027f40000(0000) knlGS:0000000000000000 > > > [ 179.987570] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b > > > [ 179.987570] CR2: 00007fff1629ebc8 CR3: 000000001dc4f000 CR4: 00000000000006e0 > > > [ 179.987570] Stack: > > > [ 179.987570] ffff88001b2239a8 ffffffff8114afde ffff88001b2239d8 ffffffff811f2e52 > > > [ 179.987570] ffff88001e0099c0 00000000fffffffb 0000000000000000 ffff880025348e88 > > > [ 179.987570] ffff88001b223a08 ffffffff812e9ad3 ffff88001b223a08 ffffffff8109b6b3 > > > [ 179.987570] Call Trace: > > > [ 179.987570] [<ffffffff8114afde>] page_endio+0x1e/0x80 > > > [ 179.987570] [<ffffffff811f2e52>] mpage_end_io+0x42/0x60 > > > [ 179.987570] [<ffffffff812e9ad3>] bio_endio+0x53/0xa0 > > > [ 179.987570] [<ffffffff8109b6b3>] ? up_read+0x23/0x40 > > > [ 179.987570] [<ffffffff81413f09>] zram_make_request+0x2a9/0x3c0 > > > [ 179.987570] [<ffffffff812ee330>] generic_make_request+0xc0/0x100 > > > [ 179.987570] [<ffffffff812ee3e5>] submit_bio+0x75/0x140 > > > [ 179.987570] [<ffffffff812ee375>] ? submit_bio+0x5/0x140 > > > [ 179.987570] [<ffffffff811f2e03>] mpage_bio_submit+0x33/0x40 > > > [ 179.987570] [<ffffffff811f3de5>] mpage_readpages+0xf5/0x110 > > > [ 179.987570] [<ffffffff811ed7a0>] ? I_BDEV+0x10/0x10 > > > [ 179.987570] [<ffffffff811ed7a0>] ? I_BDEV+0x10/0x10 > > > [ 179.987570] [<ffffffff81603241>] ? ftrace_call+0x5/0x2f > > > [ 179.987570] [<ffffffff81603241>] ? ftrace_call+0x5/0x2f > > > [ 179.987570] [<ffffffff811ee190>] ? blkdev_write_begin+0x30/0x30 > > > [ 179.987570] [<ffffffff811ed7a0>] ? I_BDEV+0x10/0x10 > > > [ 179.987570] [<ffffffff811ee1ad>] blkdev_readpages+0x1d/0x20 > > > [ 179.987570] [<ffffffff81158ed4>] __do_page_cache_readahead+0x204/0x290 > > > [ 179.987570] [<ffffffff81158d99>] ? __do_page_cache_readahead+0xc9/0x290 > > > [ 179.987570] [<ffffffff8114b045>] ? find_get_entry+0x5/0x130 > > > [ 179.987570] [<ffffffff811593cd>] force_page_cache_readahead+0x7d/0xb0 > > > [ 179.987570] [<ffffffff81159443>] page_cache_sync_readahead+0x43/0x50 > > > [ 179.987570] [<ffffffff8114d0e1>] generic_file_read_iter+0x451/0x650 > > > [ 179.987570] [<ffffffff81603241>] ? ftrace_call+0x5/0x2f > > > [ 179.987570] [<ffffffff811ed947>] blkdev_read_iter+0x37/0x40 > > > [ 179.987570] [<ffffffff811b4358>] new_sync_read+0x78/0xb0 > > > [ 179.987570] [<ffffffff811b555b>] vfs_read+0xab/0x180 > > > [ 179.987570] [<ffffffff811b5682>] SyS_read+0x52/0xb0 > > > [ 179.987570] [<ffffffff816011d2>] system_call_fastpath+0x12/0x17 > > > [ 179.987570] Code: 00 4c 8b 82 f8 00 00 00 31 d2 48 d3 ee 48 8d 3c f6 48 89 c6 49 8d 3c f8 e8 dc 9f f4 ff 5d c3 48 c7 c6 88 2c a0 81 e8 1e a8 02 00 <0f> 0b 66 66 66 2e 0f 1f 84 00 00 00 00 00 e8 bb 83 4b 00 55 48 > > > [ 179.987570] RIP [<ffffffff8114ae12>] unlock_page+0x82/0x90 > > > [ 179.987570] RSP <ffff88001b223998> > > > [ 179.987570] ---[ end trace 39c73c1d9da87ec4 ]--- > > > [ 180.030327] zram0: detected capacity change from 0 to 2147483648 > > > [ 180.033795] Adding 2097148k swap on /dev/zram0. Priority:-1 extents:1 across:2097148k SSFS > > > [ 181.978291] zram_kern_compi (2685): drop_caches: 3 > > > > > > Cc: Matthew Wilcox <willy@xxxxxxxxxxxxxxx> > > > Cc: Dave Chinner <david@xxxxxxxxxxxxx> > > > Cc: Karam Lee <karam.lee@xxxxxxx> > > > Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx> > > > --- > > > drivers/block/zram/zram_drv.c | 17 +++++++++++------ > > > 1 file changed, 11 insertions(+), 6 deletions(-) > > > > > > diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c > > > index 05e8e54551de..004d758f0c39 100644 > > > --- a/drivers/block/zram/zram_drv.c > > > +++ b/drivers/block/zram/zram_drv.c > > > @@ -947,7 +947,7 @@ static void zram_slot_free_notify(struct block_device *bdev, > > > static int zram_rw_page(struct block_device *bdev, sector_t sector, > > > struct page *page, int rw) > > > { > > > - int offset, ret; > > > + int offset, err; > > > u32 index; > > > struct zram *zram; > > > struct bio_vec bv; > > > @@ -955,13 +955,13 @@ static int zram_rw_page(struct block_device *bdev, sector_t sector, > > > zram = bdev->bd_disk->private_data; > > > if (!valid_io_request(zram, sector, PAGE_SIZE)) { > > > atomic64_inc(&zram->stats.invalid_io); > > > - ret = -EINVAL; > > > + err = -EINVAL; > > > goto out; > > > } > > > > > > down_read(&zram->init_lock); > > > if (unlikely(!init_done(zram))) { > > > - ret = -EIO; > > > + err = -EIO; > > > goto out_unlock; > > > } > > > > > > @@ -972,13 +972,18 @@ static int zram_rw_page(struct block_device *bdev, sector_t sector, > > > bv.bv_len = PAGE_SIZE; > > > bv.bv_offset = 0; > > > > > > - ret = zram_bvec_rw(zram, &bv, index, offset, rw); > > > + err = zram_bvec_rw(zram, &bv, index, offset, rw); > > > > > > out_unlock: > > > up_read(&zram->init_lock); > > > out: > > > - page_endio(page, rw, ret); > > > - return ret; > > > + page_endio(page, rw, err); > > > + > > > + /* > > > + * Return 0 prevents I/O fallback trial caused by rw_page fail > > > + * and upper layer can handle this IO error via page error. > > > + */ > > > + return 0; > > > > > > so, the patch is a one-liner. is there any reason to rename `err' to `ret'? > > 'ret' is not return value any more so I want to make it clear. > While I read this mail, I found to miss write-fail case. > if zram_bvec_rw returns error, we shouldn't invoke page_endio. :( > Will send a patch. sorry for extremly late responses, it's rather hard to answer in time. well, there is no need in a new patch, if this one has been already merged. the reson I asked is that this rename noise masks the real fix, which is just one line: return 0. -ss > Thanks. > > > > > -ss > > > > > } > > > > > > static const struct block_device_operations zram_devops = { > > > -- > > > 2.0.0 > > > > > > > -- > > To unsubscribe, send a message with 'unsubscribe linux-mm' in > > the body to majordomo@xxxxxxxxx. For more info on Linux MM, > > see: http://www.linux-mm.org/ . > > Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a> > > -- > Kind regards, > Minchan Kim > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>