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    Subject[PATCH v6 08/22] Replace xip_truncate_page with dax_truncate_page
    Date
    It takes a get_block parameter just like nobh_truncate_page() and
    block_truncate_page()

    Signed-off-by: Matthew Wilcox <matthew.r.wilcox@intel.com>
    ---
    fs/dax.c | 52 ++++++++++++++++++++++++++++++++++++++++++++++++----
    fs/ext2/inode.c | 2 +-
    include/linux/fs.h | 4 ++--
    mm/filemap_xip.c | 40 ----------------------------------------
    4 files changed, 51 insertions(+), 47 deletions(-)

    diff --git a/fs/dax.c b/fs/dax.c
    index ebcd8fd..a6a1adc 100644
    --- a/fs/dax.c
    +++ b/fs/dax.c
    @@ -302,13 +302,13 @@ static int do_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
    }

    /**
    - * dax_fault - handle a page fault on an XIP file
    + * dax_fault - handle a page fault on a DAX file
    * @vma: The virtual memory area where the fault occurred
    * @vmf: The description of the fault
    * @get_block: The filesystem method used to translate file offsets to blocks
    *
    * When a page fault occurs, filesystems may call this helper in their
    - * fault handler for XIP files.
    + * fault handler for DAX files.
    */
    int dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
    get_block_t get_block)
    @@ -326,12 +326,12 @@ int dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
    EXPORT_SYMBOL_GPL(dax_fault);

    /**
    - * dax_mkwrite - convert a read-only page to read-write in an XIP file
    + * dax_mkwrite - convert a read-only page to read-write in a DAX file
    * @vma: The virtual memory area where the fault occurred
    * @vmf: The description of the fault
    * @get_block: The filesystem method used to translate file offsets to blocks
    *
    - * XIP handles reads of holes by adding pages full of zeroes into the
    + * DAX handles reads of holes by adding pages full of zeroes into the
    * mapping. If the page is subsequenty written to, we have to allocate
    * the page on media and free the page that was in the cache.
    */
    @@ -357,3 +357,47 @@ int dax_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
    return result;
    }
    EXPORT_SYMBOL_GPL(dax_mkwrite);
    +
    +/**
    + * dax_truncate_page - handle a partial page being truncated in a DAX file
    + * @inode: The file being truncated
    + * @from: The file offset that is being truncated to
    + * @get_block: The filesystem method used to translate file offsets to blocks
    + *
    + * Similar to block_truncate_page(), this function can be called by a
    + * filesystem when it is truncating an DAX file to handle the partial page.
    + *
    + * We work in terms of PAGE_CACHE_SIZE here for commonality with
    + * block_truncate_page(), but we could go down to PAGE_SIZE if the filesystem
    + * took care of disposing of the unnecessary blocks. Even if the filesystem
    + * block size is smaller than PAGE_SIZE, we have to zero the rest of the page
    + * since the file might be mmaped.
    + */
    +int dax_truncate_page(struct inode *inode, loff_t from, get_block_t get_block)
    +{
    + struct buffer_head bh;
    + pgoff_t index = from >> PAGE_CACHE_SHIFT;
    + unsigned offset = from & (PAGE_CACHE_SIZE-1);
    + unsigned length = PAGE_CACHE_ALIGN(from) - from;
    + int err;
    +
    + /* Block boundary? Nothing to do */
    + if (!length)
    + return 0;
    +
    + memset(&bh, 0, sizeof(bh));
    + bh.b_size = PAGE_CACHE_SIZE;
    + err = get_block(inode, index, &bh, 0);
    + if (err < 0)
    + return err;
    + if (buffer_written(&bh)) {
    + void *addr;
    + err = dax_get_addr(inode, &bh, &addr);
    + if (err)
    + return err;
    + memset(addr + offset, 0, length);
    + }
    +
    + return 0;
    +}
    +EXPORT_SYMBOL_GPL(dax_truncate_page);
    diff --git a/fs/ext2/inode.c b/fs/ext2/inode.c
    index f128ebf..252481f 100644
    --- a/fs/ext2/inode.c
    +++ b/fs/ext2/inode.c
    @@ -1207,7 +1207,7 @@ static int ext2_setsize(struct inode *inode, loff_t newsize)
    inode_dio_wait(inode);

    if (IS_DAX(inode))
    - error = xip_truncate_page(inode->i_mapping, newsize);
    + error = dax_truncate_page(inode, newsize, ext2_get_block);
    else if (test_opt(inode->i_sb, NOBH))
    error = nobh_truncate_page(inode->i_mapping,
    newsize, ext2_get_block);
    diff --git a/include/linux/fs.h b/include/linux/fs.h
    index 00ad95e..02eeeb7 100644
    --- a/include/linux/fs.h
    +++ b/include/linux/fs.h
    @@ -2518,13 +2518,13 @@ extern int generic_file_open(struct inode * inode, struct file * filp);
    extern int nonseekable_open(struct inode * inode, struct file * filp);

    #ifdef CONFIG_FS_XIP
    -extern int xip_truncate_page(struct address_space *mapping, loff_t from);
    +int dax_truncate_page(struct inode *, loff_t from, get_block_t);
    ssize_t dax_do_io(int rw, struct kiocb *, struct inode *, const struct iovec *,
    loff_t, unsigned segs, get_block_t, dio_iodone_t, int flags);
    int dax_fault(struct vm_area_struct *, struct vm_fault *, get_block_t);
    int dax_mkwrite(struct vm_area_struct *, struct vm_fault *, get_block_t);
    #else
    -static inline int xip_truncate_page(struct address_space *mapping, loff_t from)
    +static inline int dax_truncate_page(struct inode *i, loff_t frm, get_block_t gb)
    {
    return 0;
    }
    diff --git a/mm/filemap_xip.c b/mm/filemap_xip.c
    index 9dd45f3..6316578 100644
    --- a/mm/filemap_xip.c
    +++ b/mm/filemap_xip.c
    @@ -21,43 +21,3 @@
    #include <asm/tlbflush.h>
    #include <asm/io.h>

    -/*
    - * truncate a page used for execute in place
    - * functionality is analog to block_truncate_page but does use get_xip_mem
    - * to get the page instead of page cache
    - */
    -int
    -xip_truncate_page(struct address_space *mapping, loff_t from)
    -{
    - pgoff_t index = from >> PAGE_CACHE_SHIFT;
    - unsigned offset = from & (PAGE_CACHE_SIZE-1);
    - unsigned blocksize;
    - unsigned length;
    - void *xip_mem;
    - unsigned long xip_pfn;
    - int err;
    -
    - BUG_ON(!mapping->a_ops->get_xip_mem);
    -
    - blocksize = 1 << mapping->host->i_blkbits;
    - length = offset & (blocksize - 1);
    -
    - /* Block boundary? Nothing to do */
    - if (!length)
    - return 0;
    -
    - length = blocksize - length;
    -
    - err = mapping->a_ops->get_xip_mem(mapping, index, 0,
    - &xip_mem, &xip_pfn);
    - if (unlikely(err)) {
    - if (err == -ENODATA)
    - /* Hole? No need to truncate */
    - return 0;
    - else
    - return err;
    - }
    - memset(xip_mem + offset, 0, length);
    - return 0;
    -}
    -EXPORT_SYMBOL_GPL(xip_truncate_page);
    --
    1.8.5.3


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