stable.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Jan Kara <jack@suse.cz>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: linux-kernel@vger.kernel.org, stable@vger.kernel.org,
	syzbot+9933e4476f365f5d5a1b@syzkaller.appspotmail.com,
	Jan Kara <jack@suse.cz>, Jens Axboe <axboe@kernel.dk>
Subject: Re: [PATCH 4.20 085/111] blockdev: Fix livelocks on loop device
Date: Mon, 21 Jan 2019 15:03:01 +0100	[thread overview]
Message-ID: <20190121140301.GA16096@quack2.suse.cz> (raw)
In-Reply-To: <20190121122505.487073207@linuxfoundation.org>

On Mon 21-01-19 14:43:19, Greg Kroah-Hartman wrote:
> 4.20-stable review patch.  If anyone has any objections, please let me know.

Greg, when applying this, you should also apply commit c8a83a6b54d0 "nbd:
Use set_blocksize() to set device blocksize". Otherwise some nbd
functionality would regress.

								Honza

> 
> ------------------
> 
> From: Jan Kara <jack@suse.cz>
> 
> commit 04906b2f542c23626b0ef6219b808406f8dddbe9 upstream.
> 
> bd_set_size() updates also block device's block size. This is somewhat
> unexpected from its name and at this point, only blkdev_open() uses this
> functionality. Furthermore, this can result in changing block size under
> a filesystem mounted on a loop device which leads to livelocks inside
> __getblk_gfp() like:
> 
> Sending NMI from CPU 0 to CPUs 1:
> NMI backtrace for cpu 1
> CPU: 1 PID: 10863 Comm: syz-executor0 Not tainted 4.18.0-rc5+ #151
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google
> 01/01/2011
> RIP: 0010:__sanitizer_cov_trace_pc+0x3f/0x50 kernel/kcov.c:106
> ...
> Call Trace:
>  init_page_buffers+0x3e2/0x530 fs/buffer.c:904
>  grow_dev_page fs/buffer.c:947 [inline]
>  grow_buffers fs/buffer.c:1009 [inline]
>  __getblk_slow fs/buffer.c:1036 [inline]
>  __getblk_gfp+0x906/0xb10 fs/buffer.c:1313
>  __bread_gfp+0x2d/0x310 fs/buffer.c:1347
>  sb_bread include/linux/buffer_head.h:307 [inline]
>  fat12_ent_bread+0x14e/0x3d0 fs/fat/fatent.c:75
>  fat_ent_read_block fs/fat/fatent.c:441 [inline]
>  fat_alloc_clusters+0x8ce/0x16e0 fs/fat/fatent.c:489
>  fat_add_cluster+0x7a/0x150 fs/fat/inode.c:101
>  __fat_get_block fs/fat/inode.c:148 [inline]
> ...
> 
> Trivial reproducer for the problem looks like:
> 
> truncate -s 1G /tmp/image
> losetup /dev/loop0 /tmp/image
> mkfs.ext4 -b 1024 /dev/loop0
> mount -t ext4 /dev/loop0 /mnt
> losetup -c /dev/loop0
> l /mnt
> 
> Fix the problem by moving initialization of a block device block size
> into a separate function and call it when needed.
> 
> Thanks to Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> for help with
> debugging the problem.
> 
> Reported-by: syzbot+9933e4476f365f5d5a1b@syzkaller.appspotmail.com
> Signed-off-by: Jan Kara <jack@suse.cz>
> Signed-off-by: Jens Axboe <axboe@kernel.dk>
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> 
> ---
>  fs/block_dev.c |   28 ++++++++++++++++++----------
>  1 file changed, 18 insertions(+), 10 deletions(-)
> 
> --- a/fs/block_dev.c
> +++ b/fs/block_dev.c
> @@ -104,6 +104,20 @@ void invalidate_bdev(struct block_device
>  }
>  EXPORT_SYMBOL(invalidate_bdev);
>  
> +static void set_init_blocksize(struct block_device *bdev)
> +{
> +	unsigned bsize = bdev_logical_block_size(bdev);
> +	loff_t size = i_size_read(bdev->bd_inode);
> +
> +	while (bsize < PAGE_SIZE) {
> +		if (size & bsize)
> +			break;
> +		bsize <<= 1;
> +	}
> +	bdev->bd_block_size = bsize;
> +	bdev->bd_inode->i_blkbits = blksize_bits(bsize);
> +}
> +
>  int set_blocksize(struct block_device *bdev, int size)
>  {
>  	/* Size must be a power of two, and between 512 and PAGE_SIZE */
> @@ -1408,18 +1422,9 @@ EXPORT_SYMBOL(check_disk_change);
>  
>  void bd_set_size(struct block_device *bdev, loff_t size)
>  {
> -	unsigned bsize = bdev_logical_block_size(bdev);
> -
>  	inode_lock(bdev->bd_inode);
>  	i_size_write(bdev->bd_inode, size);
>  	inode_unlock(bdev->bd_inode);
> -	while (bsize < PAGE_SIZE) {
> -		if (size & bsize)
> -			break;
> -		bsize <<= 1;
> -	}
> -	bdev->bd_block_size = bsize;
> -	bdev->bd_inode->i_blkbits = blksize_bits(bsize);
>  }
>  EXPORT_SYMBOL(bd_set_size);
>  
> @@ -1496,8 +1501,10 @@ static int __blkdev_get(struct block_dev
>  				}
>  			}
>  
> -			if (!ret)
> +			if (!ret) {
>  				bd_set_size(bdev,(loff_t)get_capacity(disk)<<9);
> +				set_init_blocksize(bdev);
> +			}
>  
>  			/*
>  			 * If the device is invalidated, rescan partition
> @@ -1532,6 +1539,7 @@ static int __blkdev_get(struct block_dev
>  				goto out_clear;
>  			}
>  			bd_set_size(bdev, (loff_t)bdev->bd_part->nr_sects << 9);
> +			set_init_blocksize(bdev);
>  		}
>  
>  		if (bdev->bd_bdi == &noop_backing_dev_info)
> 
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

  reply	other threads:[~2019-01-21 14:03 UTC|newest]

Thread overview: 120+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-21 13:41 [PATCH 4.20 000/111] 4.20.4-stable review Greg Kroah-Hartman
2019-01-21 13:41 ` [PATCH 4.20 001/111] tty/ldsem: Wake up readers after timed out down_write() Greg Kroah-Hartman
2019-01-21 13:41 ` [PATCH 4.20 002/111] tty: Hold tty_ldisc_lock() during tty_reopen() Greg Kroah-Hartman
2019-01-21 13:41 ` [PATCH 4.20 003/111] tty: Simplify tty->count math in tty_reopen() Greg Kroah-Hartman
2019-01-21 13:41 ` [PATCH 4.20 004/111] tty: Dont hold ldisc lock in tty_reopen() if ldisc present Greg Kroah-Hartman
2019-01-21 13:41 ` [PATCH 4.20 005/111] can: gw: ensure DLC boundaries after CAN frame modification Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 006/111] netfilter: nf_conncount: replace CONNCOUNT_LOCK_SLOTS with CONNCOUNT_SLOTS Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 007/111] netfilter: nf_conncount: dont skip eviction when age is negative Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 008/111] netfilter: nf_conncount: split gc in two phases Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 009/111] netfilter: nf_conncount: restart search when nodes have been erased Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 010/111] netfilter: nf_conncount: merge lookup and add functions Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 011/111] netfilter: nf_conncount: move all list iterations under spinlock Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 012/111] netfilter: nf_conncount: speculative garbage collection on empty lists Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 013/111] netfilter: nf_conncount: fix argument order to find_next_bit Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 014/111] mmc: sdhci-msm: Disable CDR function on TX Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 015/111] arm64/kvm: consistently handle host HCR_EL2 flags Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 016/111] arm64: Dont trap host pointer auth use to EL2 Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 017/111] ipv6: fix kernel-infoleak in ipv6_local_error() Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 018/111] net: bridge: fix a bug on using a neighbour cache entry without checking its state Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 019/111] packet: Do not leak dev refcounts on error exit Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 020/111] tcp: change txhash on SYN-data timeout Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 021/111] tun: publish tfile after its fully initialized Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 022/111] net: phy: add missing phy driver features Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 023/111] net: phy: Add missing features to PHY drivers Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 024/111] net: phy: meson-gxl: Use the genphy_soft_reset callback Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 025/111] lan743x: Remove phy_read from link status change function Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 026/111] IN_BADCLASS: fix macro to actually work Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 027/111] r8169: load Realtek PHY driver module before r8169 Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 028/111] bonding: update nest level on unlink Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 029/111] ip: on queued skb use skb_header_pointer instead of pskb_may_pull Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 030/111] r8169: dont try to read counters if chip is in a PCI power-save state Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 031/111] smc: move unhash as early as possible in smc_release() Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 032/111] crypto: sm3 - fix undefined shift by >= width of value Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 033/111] crypto: caam - fix zero-length buffer DMA mapping Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 034/111] crypto: authencesn - Avoid twice completion call in decrypt path Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 035/111] crypto: ccree - convert to use crypto_authenc_extractkeys() Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 036/111] crypto: bcm " Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 037/111] crypto: authenc - fix parsing key with misaligned rta_len Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 038/111] crypto: talitos - reorder code in talitos_edesc_alloc() Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 039/111] crypto: talitos - fix ablkcipher for CONFIG_VMAP_STACK Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 040/111] xen: Fix x86 sched_clock() interface for xen Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 041/111] Revert "btrfs: balance dirty metadata pages in btrfs_finish_ordered_io" Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 042/111] btrfs: wait on ordered extents on abort cleanup Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 043/111] Yama: Check for pid death before checking ancestry Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 044/111] scsi: core: Synchronize request queue PM status only on successful resume Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 045/111] scsi: sd: Fix cache_type_store() Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 046/111] virtio: dont allocate vqs when names[i] = NULL Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 047/111] virtio-balloon: tweak config_changed implementation Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 048/111] mips: fix n32 compat_ipc_parse_version Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 049/111] MIPS: BCM47XX: Setup struct device for the SoC Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 050/111] MIPS: lantiq: Fix IPI interrupt handling Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 051/111] MIPS: OCTEON: fix kexec support Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 052/111] drm/i915/gvt: Fix mmap range check Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 053/111] drm/rockchip: add missing of_node_put Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 054/111] OF: properties: " Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 055/111] mfd: tps6586x: Handle interrupts on suspend Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 056/111] media: v4l: ioctl: Validate num_planes for debug messages Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 057/111] media: vim2m: only cancel work if it is for right context Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 058/111] RDMA/nldev: Dont expose unsafe global rkey to regular user Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 059/111] RDMA/vmw_pvrdma: Return the correct opcode when creating WR Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 060/111] kbuild: Disable LD_DEAD_CODE_DATA_ELIMINATION with ftrace & GCC <= 4.7 Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 061/111] kbuild: fix single target build for external module Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 062/111] kbuild: mark prepare0 as PHONY to fix external module build Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 063/111] net: dsa: realtek-smi: fix OF child-node lookup Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 064/111] pstore/ram: Avoid allocation and leak of platform data Greg Kroah-Hartman
2019-01-21 13:42 ` [PATCH 4.20 065/111] SUNRPC: Fix TCP receive code on archs with flush_dcache_page() Greg Kroah-Hartman
2019-01-21 13:43 ` [PATCH 4.20 066/111] powerpc/tm: Limit TM code inside PPC_TRANSACTIONAL_MEM Greg Kroah-Hartman
2019-01-21 13:43 ` [PATCH 4.20 067/111] arm64: kaslr: ensure randomized quantities are clean to the PoC Greg Kroah-Hartman
2019-01-21 13:43 ` [PATCH 4.20 068/111] arm64: dts: marvell: armada-ap806: reserve PSCI area Greg Kroah-Hartman
2019-01-21 13:43 ` [PATCH 4.20 069/111] fbdev: offb: Fix OF node name handling Greg Kroah-Hartman
2019-01-21 13:43 ` [PATCH 4.20 070/111] Disable MSI also when pcie-octeon.pcie_disable on Greg Kroah-Hartman
2019-01-21 13:43 ` [PATCH 4.20 071/111] fix int_sqrt64() for very large numbers Greg Kroah-Hartman
2019-01-21 13:43 ` [PATCH 4.20 072/111] omap2fb: Fix stack memory disclosure Greg Kroah-Hartman
2019-01-21 13:43 ` [PATCH 4.20 073/111] media: vivid: fix error handling of kthread_run Greg Kroah-Hartman
2019-01-21 13:43 ` [PATCH 4.20 074/111] media: vivid: set min width/height to a value > 0 Greg Kroah-Hartman
2019-01-21 13:43 ` [PATCH 4.20 075/111] bpf: in __bpf_redirect_no_mac pull mac only if present Greg Kroah-Hartman
2019-01-21 13:43 ` [PATCH 4.20 076/111] ipv6: make icmp6_send() robust against null skb->dev Greg Kroah-Hartman
2019-01-21 13:43 ` [PATCH 4.20 077/111] LSM: Check for NULL cred-security on free Greg Kroah-Hartman
2019-01-21 13:43 ` [PATCH 4.20 078/111] media: vb2: vb2_mmap: move lock up Greg Kroah-Hartman
2019-01-21 13:43 ` [PATCH 4.20 079/111] sunrpc: handle ENOMEM in rpcb_getport_async Greg Kroah-Hartman
2019-01-21 13:43 ` [PATCH 4.20 080/111] netfilter: ebtables: account ebt_table_info to kmemcg Greg Kroah-Hartman
2019-01-21 13:43 ` [PATCH 4.20 081/111] block: use rcu_work instead of call_rcu to avoid sleep in softirq Greg Kroah-Hartman
2019-01-21 13:43 ` [PATCH 4.20 082/111] drm/vkms: Fix plane duplicate_state Greg Kroah-Hartman
2019-01-21 13:43 ` [PATCH 4.20 083/111] gpu/drm: Fix lock held when returning to user space Greg Kroah-Hartman
2019-01-21 13:43 ` [PATCH 4.20 084/111] selinux: fix GPF on invalid policy Greg Kroah-Hartman
2019-01-21 13:43 ` [PATCH 4.20 085/111] blockdev: Fix livelocks on loop device Greg Kroah-Hartman
2019-01-21 14:03   ` Jan Kara [this message]
2019-01-21 14:23     ` Greg Kroah-Hartman
2019-01-21 13:43 ` [PATCH 4.20 086/111] sctp: allocate sctp_sockaddr_entry with kzalloc Greg Kroah-Hartman
2019-01-21 13:43 ` [PATCH 4.20 087/111] tipc: fix uninit-value in in tipc_conn_rcv_sub Greg Kroah-Hartman
2019-01-21 13:43 ` [PATCH 4.20 088/111] tipc: fix uninit-value in tipc_nl_compat_link_reset_stats Greg Kroah-Hartman
2019-01-21 13:43 ` [PATCH 4.20 089/111] tipc: fix uninit-value in tipc_nl_compat_bearer_enable Greg Kroah-Hartman
2019-01-21 13:43 ` [PATCH 4.20 090/111] tipc: fix uninit-value in tipc_nl_compat_link_set Greg Kroah-Hartman
2019-01-21 13:43 ` [PATCH 4.20 091/111] tipc: fix uninit-value in tipc_nl_compat_name_table_dump Greg Kroah-Hartman
2019-01-21 13:43 ` [PATCH 4.20 092/111] tipc: fix uninit-value in tipc_nl_compat_doit Greg Kroah-Hartman
2019-01-21 13:43 ` [PATCH 4.20 093/111] block/loop: Dont grab "struct file" for vfs_getattr() operation Greg Kroah-Hartman
2019-01-21 13:43 ` [PATCH 4.20 094/111] block/loop: Use global lock for ioctl() operation Greg Kroah-Hartman
2019-01-21 13:43 ` [PATCH 4.20 095/111] loop: Fold __loop_release into loop_release Greg Kroah-Hartman
2019-01-21 13:43 ` [PATCH 4.20 096/111] loop: Get rid of loop_index_mutex Greg Kroah-Hartman
2019-01-21 13:43 ` [PATCH 4.20 097/111] loop: Push lo_ctl_mutex down into individual ioctls Greg Kroah-Hartman
2019-01-21 13:43 ` [PATCH 4.20 098/111] loop: Split setting of lo_state from loop_clr_fd Greg Kroah-Hartman
2019-01-21 13:43 ` [PATCH 4.20 099/111] loop: Push loop_ctl_mutex down into loop_clr_fd() Greg Kroah-Hartman
2019-01-21 13:43 ` [PATCH 4.20 100/111] loop: Push loop_ctl_mutex down to loop_get_status() Greg Kroah-Hartman
2019-01-21 13:43 ` [PATCH 4.20 101/111] loop: Push loop_ctl_mutex down to loop_set_status() Greg Kroah-Hartman
2019-01-21 13:43 ` [PATCH 4.20 102/111] loop: Push loop_ctl_mutex down to loop_set_fd() Greg Kroah-Hartman
2019-01-21 13:43 ` [PATCH 4.20 103/111] loop: Push loop_ctl_mutex down to loop_change_fd() Greg Kroah-Hartman
2019-01-21 13:43 ` [PATCH 4.20 104/111] loop: Move special partition reread handling in loop_clr_fd() Greg Kroah-Hartman
2019-01-21 13:43 ` [PATCH 4.20 105/111] loop: Move loop_reread_partitions() out of loop_ctl_mutex Greg Kroah-Hartman
2019-01-21 13:43 ` [PATCH 4.20 106/111] loop: Fix deadlock when calling blkdev_reread_part() Greg Kroah-Hartman
2019-01-21 13:43 ` [PATCH 4.20 107/111] loop: Avoid circular locking dependency between loop_ctl_mutex and bd_mutex Greg Kroah-Hartman
2019-01-21 13:43 ` [PATCH 4.20 108/111] loop: Get rid of nested acquisition of loop_ctl_mutex Greg Kroah-Hartman
2019-01-21 13:43 ` [PATCH 4.20 109/111] loop: Fix double mutex_unlock(&loop_ctl_mutex) in loop_control_ioctl() Greg Kroah-Hartman
2019-01-21 13:43 ` [PATCH 4.20 110/111] loop: drop caches if offset or block_size are changed Greg Kroah-Hartman
2019-01-21 13:43 ` [PATCH 4.20 111/111] drm/fb-helper: Ignore the value of fb_var_screeninfo.pixclock Greg Kroah-Hartman
2019-01-22 13:33 ` [PATCH 4.20 000/111] 4.20.4-stable review Naresh Kamboju
2019-01-22 16:44   ` Greg Kroah-Hartman
2019-01-22 19:24 ` Guenter Roeck
2019-01-23  6:43   ` Greg Kroah-Hartman
2019-01-22 22:25 ` shuah
2019-01-23  6:43   ` Greg Kroah-Hartman

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20190121140301.GA16096@quack2.suse.cz \
    --to=jack@suse.cz \
    --cc=axboe@kernel.dk \
    --cc=gregkh@linuxfoundation.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=stable@vger.kernel.org \
    --cc=syzbot+9933e4476f365f5d5a1b@syzkaller.appspotmail.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).