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Message-ID: <20120905190239.GK18051@quack.suse.cz>
Date: Wed, 5 Sep 2012 21:02:39 +0200
From: Jan Kara <jack@...e.cz>
To: Ian Abbott <abbotti@....co.uk>
Cc: lkml <linux-kernel@...r.kernel.org>, linux-fsdevel@...r.kernel.org,
Jan Kara <jack@...e.cz>
Subject: Re: [PATCH v4] UDF: Add support for O_DIRECT
On Wed 05-09-12 17:44:31, Ian Abbott wrote:
> Add support for the O_DIRECT flag. There are two cases to deal with:
>
> 1. Small files stored in the ICB (inode control block?): just return 0
> from the new udf_adinicb_direct_IO() handler to fall back to buffered
> I/O.
>
> 2. Larger files, not stored in the ICB: nothing special here. Just call
> blockdev_direct_IO() from our new udf_direct_IO() handler and tidy up
> any blocks instantiated outside i_size on error. This is pretty
> standard. Factor error handling code out of udf_write_begin() into new
> function udf_write_failed() so it can also be called by udf_direct_IO().
>
> Also change the whitespace in udf_aops to make it a bit neater.
Thanks! I've added the patch to my tree.
Honza
>
> Signed-off-by: Ian Abbott <abbotti@....co.uk>
> ---
> v2: Rework error handling in udf_direct_IO to avoid calling deprecated
> vmtruncate().
> v3: Rebased to next-20120904.
> v4: Removed special handling in udf_adinicb_writepage() as that turned
> out to be a bug in the handling of buffered writes for files in ICB,
> fixed by Jan Kara's patch "udf: Fix data corruption for files in
> ICB", dated 2012-09-05. I've tested it with that patch and it seems
> to work without corrupting file data in the ICB.
> ---
> fs/udf/file.c | 9 +++++++++
> fs/udf/inode.c | 52 ++++++++++++++++++++++++++++++++++++----------------
> 2 files changed, 45 insertions(+), 16 deletions(-)
>
> diff --git a/fs/udf/file.c b/fs/udf/file.c
> index d1c6093..77b5953 100644
> --- a/fs/udf/file.c
> +++ b/fs/udf/file.c
> @@ -118,11 +118,20 @@ static int udf_adinicb_write_end(struct file *file,
> return simple_write_end(file, mapping, pos, len, copied, page, fsdata);
> }
>
> +static ssize_t udf_adinicb_direct_IO(int rw, struct kiocb *iocb,
> + const struct iovec *iov,
> + loff_t offset, unsigned long nr_segs)
> +{
> + /* Fallback to buffered I/O. */
> + return 0;
> +}
> +
> const struct address_space_operations udf_adinicb_aops = {
> .readpage = udf_adinicb_readpage,
> .writepage = udf_adinicb_writepage,
> .write_begin = udf_adinicb_write_begin,
> .write_end = udf_adinicb_write_end,
> + .direct_IO = udf_adinicb_direct_IO,
> };
>
> static ssize_t udf_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
> diff --git a/fs/udf/inode.c b/fs/udf/inode.c
> index 1a0588e..b905448 100644
> --- a/fs/udf/inode.c
> +++ b/fs/udf/inode.c
> @@ -95,6 +95,22 @@ void udf_evict_inode(struct inode *inode)
> }
> }
>
> +static void udf_write_failed(struct address_space *mapping, loff_t to)
> +{
> + struct inode *inode = mapping->host;
> + struct udf_inode_info *iinfo = UDF_I(inode);
> + loff_t isize = inode->i_size;
> +
> + if (to > isize) {
> + truncate_pagecache(inode, to, isize);
> + if (iinfo->i_alloc_type != ICBTAG_FLAG_AD_IN_ICB) {
> + down_write(&iinfo->i_data_sem);
> + udf_truncate_extents(inode);
> + up_write(&iinfo->i_data_sem);
> + }
> + }
> +}
> +
> static int udf_writepage(struct page *page, struct writeback_control *wbc)
> {
> return block_write_full_page(page, udf_get_block, wbc);
> @@ -124,21 +140,24 @@ static int udf_write_begin(struct file *file, struct address_space *mapping,
> int ret;
>
> ret = block_write_begin(mapping, pos, len, flags, pagep, udf_get_block);
> - if (unlikely(ret)) {
> - struct inode *inode = mapping->host;
> - struct udf_inode_info *iinfo = UDF_I(inode);
> - loff_t isize = inode->i_size;
> -
> - if (pos + len > isize) {
> - truncate_pagecache(inode, pos + len, isize);
> - if (iinfo->i_alloc_type != ICBTAG_FLAG_AD_IN_ICB) {
> - down_write(&iinfo->i_data_sem);
> - udf_truncate_extents(inode);
> - up_write(&iinfo->i_data_sem);
> - }
> - }
> - }
> + if (unlikely(ret))
> + udf_write_failed(mapping, pos + len);
> + return ret;
> +}
>
> +static ssize_t udf_direct_IO(int rw, struct kiocb *iocb,
> + const struct iovec *iov,
> + loff_t offset, unsigned long nr_segs)
> +{
> + struct file *file = iocb->ki_filp;
> + struct address_space *mapping = file->f_mapping;
> + struct inode *inode = mapping->host;
> + ssize_t ret;
> +
> + ret = blockdev_direct_IO(rw, iocb, inode, iov, offset, nr_segs,
> + udf_get_block);
> + if (unlikely(ret < 0 && (rw && WRITE)))
> + udf_write_failed(mapping, offset + iov_length(iov, nr_segs));
> return ret;
> }
>
> @@ -152,8 +171,9 @@ const struct address_space_operations udf_aops = {
> .readpages = udf_readpages,
> .writepage = udf_writepage,
> .writepages = udf_writepages,
> - .write_begin = udf_write_begin,
> - .write_end = generic_write_end,
> + .write_begin = udf_write_begin,
> + .write_end = generic_write_end,
> + .direct_IO = udf_direct_IO,
> .bmap = udf_bmap,
> };
>
> --
> 1.7.12
>
--
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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