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Message-ID: <20141016125625.GR19075@thinkos.etherlink>
Date: Thu, 16 Oct 2014 14:56:25 +0200
From: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To: Matthew Wilcox <matthew.r.wilcox@...el.com>
Cc: linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
linux-kernel@...r.kernel.org,
Ross Zwisler <ross.zwisler@...ux.intel.com>
Subject: Re: [PATCH v11 20/21] ext4: Add DAX functionality
On 25-Sep-2014 04:33:37 PM, Matthew Wilcox wrote:
> From: Ross Zwisler <ross.zwisler@...ux.intel.com>
>
> This is a port of the DAX functionality found in the current version of
> ext2.
>
> Signed-off-by: Ross Zwisler <ross.zwisler@...ux.intel.com>
> Reviewed-by: Andreas Dilger <andreas.dilger@...el.com>
> [heavily tweaked]
> Signed-off-by: Matthew Wilcox <matthew.r.wilcox@...el.com>
> ---
> Documentation/filesystems/dax.txt | 1 +
> Documentation/filesystems/ext4.txt | 2 +
> fs/ext4/ext4.h | 6 +++
> fs/ext4/file.c | 49 ++++++++++++++++++++-
> fs/ext4/indirect.c | 18 +++++---
> fs/ext4/inode.c | 89 ++++++++++++++++++++++++++------------
> fs/ext4/namei.c | 10 ++++-
> fs/ext4/super.c | 39 ++++++++++++++++-
> 8 files changed, 177 insertions(+), 37 deletions(-)
>
> diff --git a/Documentation/filesystems/dax.txt b/Documentation/filesystems/dax.txt
> index ebcd97f..be376d9 100644
> --- a/Documentation/filesystems/dax.txt
> +++ b/Documentation/filesystems/dax.txt
> @@ -73,6 +73,7 @@ or a write()) work correctly.
>
> These filesystems may be used for inspiration:
> - ext2: the second extended filesystem, see Documentation/filesystems/ext2.txt
> +- ext4: the fourth extended filesystem, see Documentation/filesystems/ext4.txt
>
>
> Shortcomings
> diff --git a/Documentation/filesystems/ext4.txt b/Documentation/filesystems/ext4.txt
> index 919a329..9c511c4 100644
> --- a/Documentation/filesystems/ext4.txt
> +++ b/Documentation/filesystems/ext4.txt
> @@ -386,6 +386,8 @@ max_dir_size_kb=n This limits the size of directories so that any
> i_version Enable 64-bit inode version support. This option is
> off by default.
>
> +dax Use direct access if possible
> +
> Data Mode
> =========
> There are 3 different data modes:
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index b0c225c..5b38569 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -969,6 +969,11 @@ struct ext4_inode_info {
> #define EXT4_MOUNT_ERRORS_MASK 0x00070
> #define EXT4_MOUNT_MINIX_DF 0x00080 /* Mimics the Minix statfs */
> #define EXT4_MOUNT_NOLOAD 0x00100 /* Don't use existing journal*/
> +#ifdef CONFIG_FS_DAX
> +#define EXT4_MOUNT_DAX 0x00200 /* Execute in place */
Execute in place -> Direct Access stuff... (comment above)
> +#else
> +#define EXT4_MOUNT_DAX 0
> +#endif
> #define EXT4_MOUNT_DATA_FLAGS 0x00C00 /* Mode for data writes: */
> #define EXT4_MOUNT_JOURNAL_DATA 0x00400 /* Write data to journal */
> #define EXT4_MOUNT_ORDERED_DATA 0x00800 /* Flush data before commit */
> @@ -2574,6 +2579,7 @@ extern const struct file_operations ext4_dir_operations;
> /* file.c */
> extern const struct inode_operations ext4_file_inode_operations;
> extern const struct file_operations ext4_file_operations;
> +extern const struct file_operations ext4_dax_file_operations;
> extern loff_t ext4_llseek(struct file *file, loff_t offset, int origin);
>
> /* inline.c */
> diff --git a/fs/ext4/file.c b/fs/ext4/file.c
> index aca7b24..9c7bde5 100644
> --- a/fs/ext4/file.c
> +++ b/fs/ext4/file.c
> @@ -95,7 +95,7 @@ ext4_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
> struct inode *inode = file_inode(iocb->ki_filp);
> struct mutex *aio_mutex = NULL;
> struct blk_plug plug;
> - int o_direct = file->f_flags & O_DIRECT;
> + int o_direct = io_is_direct(file);
> int overwrite = 0;
> size_t length = iov_iter_count(from);
> ssize_t ret;
> @@ -191,6 +191,27 @@ errout:
> return ret;
> }
>
> +#ifdef CONFIG_FS_DAX
> +static int ext4_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
> +{
> + return dax_fault(vma, vmf, ext4_get_block);
> + /* Is this the right get_block? */
perhaps this needs a TODO or FIXME or XXX to make sure an ext4
maintainer does not miss this question.
> +}
> +
> +static int ext4_dax_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
> +{
> + return dax_mkwrite(vma, vmf, ext4_get_block);
> +}
> +
> +static const struct vm_operations_struct ext4_dax_vm_ops = {
> + .fault = ext4_dax_fault,
> + .page_mkwrite = ext4_dax_mkwrite,
> + .remap_pages = generic_file_remap_pages,
> +};
> +#else
> +#define ext4_dax_vm_ops ext4_file_vm_ops
> +#endif
> +
> static const struct vm_operations_struct ext4_file_vm_ops = {
> .fault = filemap_fault,
> .map_pages = filemap_map_pages,
> @@ -201,7 +222,12 @@ static const struct vm_operations_struct ext4_file_vm_ops = {
> static int ext4_file_mmap(struct file *file, struct vm_area_struct *vma)
> {
> file_accessed(file);
> - vma->vm_ops = &ext4_file_vm_ops;
> + if (IS_DAX(file_inode(file))) {
> + vma->vm_ops = &ext4_dax_vm_ops;
> + vma->vm_flags |= VM_MIXEDMAP;
> + } else {
> + vma->vm_ops = &ext4_file_vm_ops;
> + }
> return 0;
> }
>
> @@ -600,6 +626,25 @@ const struct file_operations ext4_file_operations = {
> .fallocate = ext4_fallocate,
> };
>
> +#ifdef CONFIG_FS_DAX
> +const struct file_operations ext4_dax_file_operations = {
> + .llseek = ext4_llseek,
> + .read = new_sync_read,
> + .write = new_sync_write,
> + .read_iter = generic_file_read_iter,
> + .write_iter = ext4_file_write_iter,
> + .unlocked_ioctl = ext4_ioctl,
> +#ifdef CONFIG_COMPAT
> + .compat_ioctl = ext4_compat_ioctl,
> +#endif
> + .mmap = ext4_file_mmap,
> + .open = ext4_file_open,
> + .release = ext4_release_file,
> + .fsync = ext4_sync_file,
> + .fallocate = ext4_fallocate,
Perhaps adding comments saying that .splice_read and .splice_write are
unavailable here would help understanding why we need a different file
operations structure.
> +};
> +#endif
> +
> const struct inode_operations ext4_file_inode_operations = {
> .setattr = ext4_setattr,
> .getattr = ext4_getattr,
> diff --git a/fs/ext4/indirect.c b/fs/ext4/indirect.c
> index e75f840..fa9ec8d 100644
> --- a/fs/ext4/indirect.c
> +++ b/fs/ext4/indirect.c
> @@ -691,14 +691,22 @@ retry:
> inode_dio_done(inode);
> goto locked;
> }
> - ret = __blockdev_direct_IO(rw, iocb, inode,
> - inode->i_sb->s_bdev, iter, offset,
> - ext4_get_block, NULL, NULL, 0);
> + if (IS_DAX(inode))
> + ret = dax_do_io(rw, iocb, inode, iter, offset,
> + ext4_get_block, NULL, 0);
> + else
> + ret = __blockdev_direct_IO(rw, iocb, inode,
> + inode->i_sb->s_bdev, iter, offset,
> + ext4_get_block, NULL, NULL, 0);
> inode_dio_done(inode);
> } else {
> locked:
> - ret = blockdev_direct_IO(rw, iocb, inode, iter,
> - offset, ext4_get_block);
> + if (IS_DAX(inode))
> + ret = dax_do_io(rw, iocb, inode, iter, offset,
> + ext4_get_block, NULL, DIO_LOCKING);
> + else
> + ret = blockdev_direct_IO(rw, iocb, inode, iter,
> + offset, ext4_get_block);
>
> if (unlikely((rw & WRITE) && ret < 0)) {
> loff_t isize = i_size_read(inode);
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 3aa26e9..542205f 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -676,6 +676,18 @@ has_zeroout:
> return retval;
> }
>
> +static void ext4_end_io_unwritten(struct buffer_head *bh, int uptodate)
> +{
> + struct inode *inode = bh->b_assoc_map->host;
> + /* XXX: breaks on 32-bit > 16GB. Is that even supported? */
Good question! It would be interesting to get an answer :)
> + loff_t offset = (loff_t)(uintptr_t)bh->b_private << inode->i_blkbits;
> + int err;
missing newline.
> + if (!uptodate)
> + return;
> + WARN_ON(!buffer_unwritten(bh));
> + err = ext4_convert_unwritten_extents(NULL, inode, offset, bh->b_size);
err is simply unused here, that does not look good (silent failure).
> +}
> +
> /* Maximum number of blocks we map for direct IO at once. */
> #define DIO_MAX_BLOCKS 4096
>
> @@ -713,6 +725,11 @@ static int _ext4_get_block(struct inode *inode, sector_t iblock,
>
> map_bh(bh, inode->i_sb, map.m_pblk);
> bh->b_state = (bh->b_state & ~EXT4_MAP_FLAGS) | map.m_flags;
> + if (IS_DAX(inode) && buffer_unwritten(bh) && !io_end) {
> + bh->b_assoc_map = inode->i_mapping;
> + bh->b_private = (void *)(unsigned long)iblock;
> + bh->b_end_io = ext4_end_io_unwritten;
> + }
> if (io_end && io_end->flag & EXT4_IO_END_UNWRITTEN)
> set_buffer_defer_completion(bh);
> bh->b_size = inode->i_sb->s_blocksize * map.m_len;
> @@ -3043,13 +3060,14 @@ static ssize_t ext4_ext_direct_IO(int rw, struct kiocb *iocb,
> get_block_func = ext4_get_block_write;
> dio_flags = DIO_LOCKING;
> }
> - ret = __blockdev_direct_IO(rw, iocb, inode,
> - inode->i_sb->s_bdev, iter,
> - offset,
> - get_block_func,
> - ext4_end_io_dio,
> - NULL,
> - dio_flags);
> + if (IS_DAX(inode))
> + ret = dax_do_io(rw, iocb, inode, iter, offset, get_block_func,
> + ext4_end_io_dio, dio_flags);
> + else
> + ret = __blockdev_direct_IO(rw, iocb, inode,
> + inode->i_sb->s_bdev, iter, offset,
> + get_block_func,
> + ext4_end_io_dio, NULL, dio_flags);
>
> /*
> * Put our reference to io_end. This can free the io_end structure e.g.
> @@ -3213,19 +3231,12 @@ void ext4_set_aops(struct inode *inode)
> inode->i_mapping->a_ops = &ext4_aops;
> }
>
> -/*
> - * ext4_block_zero_page_range() zeros out a mapping of length 'length'
> - * starting from file offset 'from'. The range to be zero'd must
> - * be contained with in one block. If the specified range exceeds
> - * the end of the block it will be shortened to end of the block
> - * that cooresponds to 'from'
> - */
> -static int ext4_block_zero_page_range(handle_t *handle,
> +static int __ext4_block_zero_page_range(handle_t *handle,
> struct address_space *mapping, loff_t from, loff_t length)
> {
> ext4_fsblk_t index = from >> PAGE_CACHE_SHIFT;
> unsigned offset = from & (PAGE_CACHE_SIZE-1);
> - unsigned blocksize, max, pos;
> + unsigned blocksize, pos;
> ext4_lblk_t iblock;
> struct inode *inode = mapping->host;
> struct buffer_head *bh;
> @@ -3238,14 +3249,6 @@ static int ext4_block_zero_page_range(handle_t *handle,
> return -ENOMEM;
>
> blocksize = inode->i_sb->s_blocksize;
> - max = blocksize - (offset & (blocksize - 1));
> -
> - /*
> - * correct length if it does not fall between
> - * 'from' and the end of the block
> - */
> - if (length > max || length < 0)
> - length = max;
>
> iblock = index << (PAGE_CACHE_SHIFT - inode->i_sb->s_blocksize_bits);
>
> @@ -3311,6 +3314,33 @@ unlock:
> }
>
> /*
> + * ext4_block_zero_page_range() zeros out a mapping of length 'length'
> + * starting from file offset 'from'. The range to be zero'd must
> + * be contained with in one block. If the specified range exceeds
> + * the end of the block it will be shortened to end of the block
> + * that cooresponds to 'from'
> + */
> +static int ext4_block_zero_page_range(handle_t *handle,
> + struct address_space *mapping, loff_t from, loff_t length)
> +{
> + struct inode *inode = mapping->host;
> + unsigned offset = from & (PAGE_CACHE_SIZE-1);
> + unsigned blocksize = inode->i_sb->s_blocksize;
> + unsigned max = blocksize - (offset & (blocksize - 1));
> +
> + /*
> + * correct length if it does not fall between
> + * 'from' and the end of the block
> + */
Shouldn't a length < 0 be treated as an error instead ?
> + if (length > max || length < 0)
> + length = max;
> +
> + if (IS_DAX(inode))
> + return dax_zero_page_range(inode, from, length, ext4_get_block);
> + return __ext4_block_zero_page_range(handle, mapping, from, length);
> +}
> +
> +/*
> * ext4_block_truncate_page() zeroes out a mapping from file offset `from'
> * up to the end of the block which corresponds to `from'.
> * This required during truncate. We need to physically zero the tail end
> @@ -3831,8 +3861,10 @@ void ext4_set_inode_flags(struct inode *inode)
> new_fl |= S_NOATIME;
> if (flags & EXT4_DIRSYNC_FL)
> new_fl |= S_DIRSYNC;
> + if (test_opt(inode->i_sb, DAX))
> + new_fl |= S_DAX;
> inode_set_flags(inode, new_fl,
> - S_SYNC|S_APPEND|S_IMMUTABLE|S_NOATIME|S_DIRSYNC);
> + S_SYNC|S_APPEND|S_IMMUTABLE|S_NOATIME|S_DIRSYNC|S_DAX);
> }
>
> /* Propagate flags from i_flags to EXT4_I(inode)->i_flags */
> @@ -4086,7 +4118,10 @@ struct inode *ext4_iget(struct super_block *sb, unsigned long ino)
>
> if (S_ISREG(inode->i_mode)) {
> inode->i_op = &ext4_file_inode_operations;
> - inode->i_fop = &ext4_file_operations;
> + if (test_opt(inode->i_sb, DAX))
> + inode->i_fop = &ext4_dax_file_operations;
> + else
> + inode->i_fop = &ext4_file_operations;
> ext4_set_aops(inode);
> } else if (S_ISDIR(inode->i_mode)) {
> inode->i_op = &ext4_dir_inode_operations;
> @@ -4556,7 +4591,7 @@ int ext4_setattr(struct dentry *dentry, struct iattr *attr)
> * Truncate pagecache after we've waited for commit
> * in data=journal mode to make pages freeable.
> */
> - truncate_pagecache(inode, inode->i_size);
> + truncate_pagecache(inode, inode->i_size);
> }
> /*
> * We want to call ext4_truncate() even if attr->ia_size ==
> diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
> index 603e4eb..8d744a5 100644
> --- a/fs/ext4/namei.c
> +++ b/fs/ext4/namei.c
> @@ -2264,7 +2264,10 @@ retry:
> err = PTR_ERR(inode);
> if (!IS_ERR(inode)) {
> inode->i_op = &ext4_file_inode_operations;
> - inode->i_fop = &ext4_file_operations;
> + if (test_opt(inode->i_sb, DAX))
> + inode->i_fop = &ext4_dax_file_operations;
> + else
> + inode->i_fop = &ext4_file_operations;
> ext4_set_aops(inode);
> err = ext4_add_nondir(handle, dentry, inode);
> if (!err && IS_DIRSYNC(dir))
> @@ -2328,7 +2331,10 @@ retry:
> err = PTR_ERR(inode);
> if (!IS_ERR(inode)) {
> inode->i_op = &ext4_file_inode_operations;
> - inode->i_fop = &ext4_file_operations;
> + if (test_opt(inode->i_sb, DAX))
> + inode->i_fop = &ext4_dax_file_operations;
> + else
> + inode->i_fop = &ext4_file_operations;
> ext4_set_aops(inode);
> d_tmpfile(dentry, inode);
> err = ext4_orphan_add(handle, inode);
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index 0b28b36..b94b6b9 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -1162,7 +1162,7 @@ enum {
> Opt_usrjquota, Opt_grpjquota, Opt_offusrjquota, Opt_offgrpjquota,
> Opt_jqfmt_vfsold, Opt_jqfmt_vfsv0, Opt_jqfmt_vfsv1, Opt_quota,
> Opt_noquota, Opt_barrier, Opt_nobarrier, Opt_err,
> - Opt_usrquota, Opt_grpquota, Opt_i_version,
> + Opt_usrquota, Opt_grpquota, Opt_i_version, Opt_dax,
> Opt_stripe, Opt_delalloc, Opt_nodelalloc, Opt_mblk_io_submit,
> Opt_nomblk_io_submit, Opt_block_validity, Opt_noblock_validity,
> Opt_inode_readahead_blks, Opt_journal_ioprio,
> @@ -1224,6 +1224,7 @@ static const match_table_t tokens = {
> {Opt_barrier, "barrier"},
> {Opt_nobarrier, "nobarrier"},
> {Opt_i_version, "i_version"},
> + {Opt_dax, "dax"},
> {Opt_stripe, "stripe=%u"},
> {Opt_delalloc, "delalloc"},
> {Opt_nodelalloc, "nodelalloc"},
> @@ -1406,6 +1407,7 @@ static const struct mount_opts {
> {Opt_min_batch_time, 0, MOPT_GTE0},
> {Opt_inode_readahead_blks, 0, MOPT_GTE0},
> {Opt_init_itable, 0, MOPT_GTE0},
> + {Opt_dax, EXT4_MOUNT_DAX, MOPT_SET},
> {Opt_stripe, 0, MOPT_GTE0},
> {Opt_resuid, 0, MOPT_GTE0},
> {Opt_resgid, 0, MOPT_GTE0},
> @@ -1642,6 +1644,11 @@ static int handle_mount_opt(struct super_block *sb, char *opt, int token,
> }
> sbi->s_jquota_fmt = m->mount_opt;
> #endif
> +#ifndef CONFIG_FS_DAX
> + } else if (token == Opt_dax) {
> + ext4_msg(sb, KERN_INFO, "dax option not supported");
> + return -1;
> +#endif
> } else {
> if (!args->from)
> arg = 1;
> @@ -3572,6 +3579,11 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
> "both data=journal and dioread_nolock");
> goto failed_mount;
> }
> + if (test_opt(sb, DAX)) {
> + ext4_msg(sb, KERN_ERR, "can't mount with "
> + "both data=journal and dax");
This limitation regarding ext4 and dax should be documented in dax
Documentation.
Thanks,
Mathieu
> + goto failed_mount;
> + }
> if (test_opt(sb, DELALLOC))
> clear_opt(sb, DELALLOC);
> }
> @@ -3635,6 +3647,19 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
> goto failed_mount;
> }
>
> + if (sbi->s_mount_opt & EXT4_MOUNT_DAX) {
> + if (blocksize != PAGE_SIZE) {
> + ext4_msg(sb, KERN_ERR,
> + "error: unsupported blocksize for dax");
> + goto failed_mount;
> + }
> + if (!sb->s_bdev->bd_disk->fops->direct_access) {
> + ext4_msg(sb, KERN_ERR,
> + "error: device does not support dax");
> + goto failed_mount;
> + }
> + }
> +
> if (sb->s_blocksize != blocksize) {
> /* Validate the filesystem blocksize */
> if (!sb_set_blocksize(sb, blocksize)) {
> @@ -4837,6 +4862,18 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
> err = -EINVAL;
> goto restore_opts;
> }
> + if (test_opt(sb, DAX)) {
> + ext4_msg(sb, KERN_ERR, "can't mount with "
> + "both data=journal and dax");
> + err = -EINVAL;
> + goto restore_opts;
> + }
> + }
> +
> + if ((sbi->s_mount_opt ^ old_opts.s_mount_opt) & EXT4_MOUNT_DAX) {
> + ext4_msg(sb, KERN_WARNING, "warning: refusing change of "
> + "dax flag with busy inodes while remounting");
> + sbi->s_mount_opt ^= EXT4_MOUNT_DAX;
> }
>
> if (sbi->s_mount_flags & EXT4_MF_FS_ABORTED)
> --
> 2.1.0
>
> --
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>
>
--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
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