| Message ID | 20150129020025.GE9981@birch.djwong.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wednesday 28 January 2015 18:00:25 Darrick J. Wong wrote: > Create a new ioctl to expose the block layer's newfound ability to > issue either a zeroing discard, a WRITE SAME with a zero page, or a > regular write with the zero page. This BLKZEROOUT2 ioctl takes > {start, length, flags} as parameters. So far, the only flag available > is to enable the zeroing discard part -- without it, the call invokes > the old BLKZEROOUT behavior. start and length have the same meaning > as in BLKZEROOUT. > > Furthermore, because BLKZEROOUT2 issues commands directly to the > storage device, we must invalidate the page cache (as a regular > O_DIRECT write would do) to avoid returning stale cache contents at a > later time. > > This patch depends on "block: Add discard flag to > blkdev_issue_zeroout() function" in Jens' for-3.20/core branch. > > Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> > Would this work ok for devices that fill discarded areas with all-ones instead of all-zeroes? I believe SD cards can do either. Arnd -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
> -----Original Message----- > From: linux-kernel-owner@vger.kernel.org [mailto:linux-kernel- > owner@vger.kernel.org] On Behalf Of Arnd Bergmann > Sent: Thursday, 29 January, 2015 4:03 AM > To: Darrick J. Wong > Cc: Jens Axboe; Christoph Hellwig; linux-kernel@vger.kernel.org; linux- > fsdevel@vger.kernel.org; linux-api@vger.kernel.org; Jeff Layton; J. Bruce > Fields > Subject: Re: [RESEND] [PATCH] block: create ioctl to discard-or-zeroout a > range of blocks > > On Wednesday 28 January 2015 18:00:25 Darrick J. Wong wrote: > > Create a new ioctl to expose the block layer's newfound ability to > > issue either a zeroing discard, a WRITE SAME with a zero page, or a > > regular write with the zero page. This BLKZEROOUT2 ioctl takes > > {start, length, flags} as parameters. So far, the only flag available > > is to enable the zeroing discard part -- without it, the call invokes > > the old BLKZEROOUT behavior. start and length have the same meaning > > as in BLKZEROOUT. > > > > Furthermore, because BLKZEROOUT2 issues commands directly to the > > storage device, we must invalidate the page cache (as a regular > > O_DIRECT write would do) to avoid returning stale cache contents at a > > later time. > > > > This patch depends on "block: Add discard flag to > > blkdev_issue_zeroout() function" in Jens' for-3.20/core branch. > > > > Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> > > > > Would this work ok for devices that fill discarded areas with all-ones > instead of all-zeroes? I believe SD cards can do either. > > Arnd RAID software stacks need predictable data, and 0 is a lot easier to deal with than 0xff in Galois field (XOR-based) math. The SCSI and ATA standards both define bits to report if the device is designed to return 0 after discard; they don't have a way to report that any other particular non-zero value is returned. --- Rob Elliott HP Server Storage -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Thu, Jan 29, 2015 at 11:02:58AM +0100, Arnd Bergmann wrote: > On Wednesday 28 January 2015 18:00:25 Darrick J. Wong wrote: > > Create a new ioctl to expose the block layer's newfound ability to > > issue either a zeroing discard, a WRITE SAME with a zero page, or a > > regular write with the zero page. This BLKZEROOUT2 ioctl takes > > {start, length, flags} as parameters. So far, the only flag available > > is to enable the zeroing discard part -- without it, the call invokes > > the old BLKZEROOUT behavior. start and length have the same meaning > > as in BLKZEROOUT. > > > > Furthermore, because BLKZEROOUT2 issues commands directly to the > > storage device, we must invalidate the page cache (as a regular > > O_DIRECT write would do) to avoid returning stale cache contents at a > > later time. > > > > This patch depends on "block: Add discard flag to > > blkdev_issue_zeroout() function" in Jens' for-3.20/core branch. > > > > Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> > > > > Would this work ok for devices that fill discarded areas with all-ones > instead of all-zeroes? I believe SD cards can do either. It won't do all-ones, because the underlying blkdev_issue_zeroout call only knows how to tell the device to write zeroes or perform a discard if the flag is set and the device is whitelisted. This patch only exposes the existing kernel call to userspace. (All-ones could be plumbed into the storage stack, but that would have to be a separate patch.) --D > > Arnd > -- > To unsubscribe from this list: send the line "unsubscribe linux-api" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Thursday 29 January 2015 11:01:02 Darrick J. Wong wrote: > It won't do all-ones, because the underlying blkdev_issue_zeroout call only > knows how to tell the device to write zeroes or perform a discard if the flag > is set and the device is whitelisted. This patch only exposes the existing > kernel call to userspace. > > (All-ones could be plumbed into the storage stack, but that would have to be a > separate patch.) I see. I've just checked the code in the mmc core and it seems to get the correct information for both mmc and sd devices (they use different bits to announce the feature). So as long as the devices follow the spec, everything is fine here. Thanks Darrick and Robert for the quick reply! Arnd -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
>>>>> "Darrick" == Darrick J Wong <darrick.wong@oracle.com> writes: Darrick> Create a new ioctl to expose the block layer's newfound ability Darrick> to issue either a zeroing discard, a WRITE SAME with a zero Darrick> page, or a regular write with the zero page. This BLKZEROOUT2 Darrick> ioctl takes {start, length, flags} as parameters. So far, the Darrick> only flag available is to enable the zeroing discard part -- Darrick> without it, the call invokes the old BLKZEROOUT behavior. Darrick> start and length have the same meaning as in BLKZEROOUT. Darrick> Furthermore, because BLKZEROOUT2 issues commands directly to Darrick> the storage device, we must invalidate the page cache (as a Darrick> regular O_DIRECT write would do) to avoid returning stale cache Darrick> contents at a later time. Looks good to me, Darrick. Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
So, uh, it's been a couple of weeks... Jens: Any comments? Nobody's objected to either the function or the interface; can this go in -next? --D On Wed, Jan 28, 2015 at 06:00:25PM -0800, Darrick J. Wong wrote: > Create a new ioctl to expose the block layer's newfound ability to > issue either a zeroing discard, a WRITE SAME with a zero page, or a > regular write with the zero page. This BLKZEROOUT2 ioctl takes > {start, length, flags} as parameters. So far, the only flag available > is to enable the zeroing discard part -- without it, the call invokes > the old BLKZEROOUT behavior. start and length have the same meaning > as in BLKZEROOUT. > > Furthermore, because BLKZEROOUT2 issues commands directly to the > storage device, we must invalidate the page cache (as a regular > O_DIRECT write would do) to avoid returning stale cache contents at a > later time. > > This patch depends on "block: Add discard flag to > blkdev_issue_zeroout() function" in Jens' for-3.20/core branch. > > Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> > --- > block/ioctl.c | 45 ++++++++++++++++++++++++++++++++++++++------- > include/uapi/linux/fs.h | 7 +++++++ > 2 files changed, 45 insertions(+), 7 deletions(-) > > diff --git a/block/ioctl.c b/block/ioctl.c > index 7d8befd..ff623d5 100644 > --- a/block/ioctl.c > +++ b/block/ioctl.c > @@ -186,19 +186,39 @@ static int blk_ioctl_discard(struct block_device *bdev, uint64_t start, > } > > static int blk_ioctl_zeroout(struct block_device *bdev, uint64_t start, > - uint64_t len) > + uint64_t len, uint32_t flags) > { > + int ret; > + struct address_space *mapping; > + uint64_t end = start + len - 1; > + > + if (flags & ~BLKZEROOUT2_DISCARD_OK) > + return -EINVAL; > if (start & 511) > return -EINVAL; > if (len & 511) > return -EINVAL; > - start >>= 9; > - len >>= 9; > - > - if (start + len > (i_size_read(bdev->bd_inode) >> 9)) > + if (end >= i_size_read(bdev->bd_inode)) > return -EINVAL; > > - return blkdev_issue_zeroout(bdev, start, len, GFP_KERNEL, false); > + /* Invalidate the page cache, including dirty pages */ > + mapping = bdev->bd_inode->i_mapping; > + truncate_inode_pages_range(mapping, start, end); > + > + ret = blkdev_issue_zeroout(bdev, start >> 9, len >> 9, GFP_KERNEL, > + flags & BLKZEROOUT2_DISCARD_OK); > + if (ret) > + goto out; > + > + /* > + * Invalidate again; if someone wandered in and dirtied a page, > + * the caller will be given -EBUSY. > + */ > + ret = invalidate_inode_pages2_range(mapping, > + start >> PAGE_CACHE_SHIFT, > + end >> PAGE_CACHE_SHIFT); > +out: > + return ret; > } > > static int put_ushort(unsigned long arg, unsigned short val) > @@ -326,7 +346,18 @@ int blkdev_ioctl(struct block_device *bdev, fmode_t mode, unsigned cmd, > if (copy_from_user(range, (void __user *)arg, sizeof(range))) > return -EFAULT; > > - return blk_ioctl_zeroout(bdev, range[0], range[1]); > + return blk_ioctl_zeroout(bdev, range[0], range[1], 0); > + } > + case BLKZEROOUT2: { > + struct blkzeroout2 p; > + > + if (!(mode & FMODE_WRITE)) > + return -EBADF; > + > + if (copy_from_user(&p, (void __user *)arg, sizeof(p))) > + return -EFAULT; > + > + return blk_ioctl_zeroout(bdev, p.start, p.length, p.flags); > } > > case HDIO_GETGEO: { > diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h > index 3735fa0..54d24ea 100644 > --- a/include/uapi/linux/fs.h > +++ b/include/uapi/linux/fs.h > @@ -150,6 +150,13 @@ struct inodes_stat_t { > #define BLKSECDISCARD _IO(0x12,125) > #define BLKROTATIONAL _IO(0x12,126) > #define BLKZEROOUT _IO(0x12,127) > +struct blkzeroout2 { > + __u64 start; > + __u64 length; > + __u32 flags; > +}; > +#define BLKZEROOUT2_DISCARD_OK 1 > +#define BLKZEROOUT2 _IOR(0x12, 127, struct blkzeroout2) > > #define BMAP_IOCTL 1 /* obsolete - kept for compatibility */ > #define FIBMAP _IO(0x00,1) /* bmap access */ > -- > To unsubscribe from this list: send the line "unsubscribe linux-api" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/block/ioctl.c b/block/ioctl.c index 7d8befd..ff623d5 100644 --- a/block/ioctl.c +++ b/block/ioctl.c @@ -186,19 +186,39 @@ static int blk_ioctl_discard(struct block_device *bdev, uint64_t start, } static int blk_ioctl_zeroout(struct block_device *bdev, uint64_t start, - uint64_t len) + uint64_t len, uint32_t flags) { + int ret; + struct address_space *mapping; + uint64_t end = start + len - 1; + + if (flags & ~BLKZEROOUT2_DISCARD_OK) + return -EINVAL; if (start & 511) return -EINVAL; if (len & 511) return -EINVAL; - start >>= 9; - len >>= 9; - - if (start + len > (i_size_read(bdev->bd_inode) >> 9)) + if (end >= i_size_read(bdev->bd_inode)) return -EINVAL; - return blkdev_issue_zeroout(bdev, start, len, GFP_KERNEL, false); + /* Invalidate the page cache, including dirty pages */ + mapping = bdev->bd_inode->i_mapping; + truncate_inode_pages_range(mapping, start, end); + + ret = blkdev_issue_zeroout(bdev, start >> 9, len >> 9, GFP_KERNEL, + flags & BLKZEROOUT2_DISCARD_OK); + if (ret) + goto out; + + /* + * Invalidate again; if someone wandered in and dirtied a page, + * the caller will be given -EBUSY. + */ + ret = invalidate_inode_pages2_range(mapping, + start >> PAGE_CACHE_SHIFT, + end >> PAGE_CACHE_SHIFT); +out: + return ret; } static int put_ushort(unsigned long arg, unsigned short val) @@ -326,7 +346,18 @@ int blkdev_ioctl(struct block_device *bdev, fmode_t mode, unsigned cmd, if (copy_from_user(range, (void __user *)arg, sizeof(range))) return -EFAULT; - return blk_ioctl_zeroout(bdev, range[0], range[1]); + return blk_ioctl_zeroout(bdev, range[0], range[1], 0); + } + case BLKZEROOUT2: { + struct blkzeroout2 p; + + if (!(mode & FMODE_WRITE)) + return -EBADF; + + if (copy_from_user(&p, (void __user *)arg, sizeof(p))) + return -EFAULT; + + return blk_ioctl_zeroout(bdev, p.start, p.length, p.flags); } case HDIO_GETGEO: { diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h index 3735fa0..54d24ea 100644 --- a/include/uapi/linux/fs.h +++ b/include/uapi/linux/fs.h @@ -150,6 +150,13 @@ struct inodes_stat_t { #define BLKSECDISCARD _IO(0x12,125) #define BLKROTATIONAL _IO(0x12,126) #define BLKZEROOUT _IO(0x12,127) +struct blkzeroout2 { + __u64 start; + __u64 length; + __u32 flags; +}; +#define BLKZEROOUT2_DISCARD_OK 1 +#define BLKZEROOUT2 _IOR(0x12, 127, struct blkzeroout2) #define BMAP_IOCTL 1 /* obsolete - kept for compatibility */ #define FIBMAP _IO(0x00,1) /* bmap access */
Create a new ioctl to expose the block layer's newfound ability to issue either a zeroing discard, a WRITE SAME with a zero page, or a regular write with the zero page. This BLKZEROOUT2 ioctl takes {start, length, flags} as parameters. So far, the only flag available is to enable the zeroing discard part -- without it, the call invokes the old BLKZEROOUT behavior. start and length have the same meaning as in BLKZEROOUT. Furthermore, because BLKZEROOUT2 issues commands directly to the storage device, we must invalidate the page cache (as a regular O_DIRECT write would do) to avoid returning stale cache contents at a later time. This patch depends on "block: Add discard flag to blkdev_issue_zeroout() function" in Jens' for-3.20/core branch. Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> --- block/ioctl.c | 45 ++++++++++++++++++++++++++++++++++++++------- include/uapi/linux/fs.h | 7 +++++++ 2 files changed, 45 insertions(+), 7 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html