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    Subject[V2 PATCH 2/2] fs: wire up .truncate_range and .fallocate
    Date
    V1->V2:
    Move tmpfs stuff into shmem_fallocate(), suggested by Christoph.

    As Hugh suggested, with FALLOC_FL_PUNCH_HOLE, we can use do_fallocate()
    to implement madvise_remove and finally remove .truncate_range call back.

    Cc: Hugh Dickins <hughd@google.com>
    Cc: Christoph Hellwig <hch@lst.de>
    Cc: Al Viro <viro@zeniv.linux.org.uk>
    Signed-off-by: WANG Cong <amwang@redhat.com>

    ---
    include/linux/fs.h | 1 -
    include/linux/mm.h | 2 +-
    mm/madvise.c | 6 +++---
    mm/shmem.c | 12 +++++++++++-
    mm/truncate.c | 22 +++++-----------------
    5 files changed, 20 insertions(+), 23 deletions(-)

    diff --git a/include/linux/fs.h b/include/linux/fs.h
    index e313022..266df73 100644
    --- a/include/linux/fs.h
    +++ b/include/linux/fs.h
    @@ -1635,7 +1635,6 @@ struct inode_operations {
    ssize_t (*getxattr) (struct dentry *, const char *, void *, size_t);
    ssize_t (*listxattr) (struct dentry *, char *, size_t);
    int (*removexattr) (struct dentry *, const char *);
    - void (*truncate_range)(struct inode *, loff_t, loff_t);
    int (*fiemap)(struct inode *, struct fiemap_extent_info *, u64 start,
    u64 len);
    } ____cacheline_aligned;
    diff --git a/include/linux/mm.h b/include/linux/mm.h
    index 3dc3a8c..0582ce8 100644
    --- a/include/linux/mm.h
    +++ b/include/linux/mm.h
    @@ -951,7 +951,7 @@ static inline void unmap_shared_mapping_range(struct address_space *mapping,
    extern void truncate_pagecache(struct inode *inode, loff_t old, loff_t new);
    extern void truncate_setsize(struct inode *inode, loff_t newsize);
    extern int vmtruncate(struct inode *inode, loff_t offset);
    -extern int vmtruncate_range(struct inode *inode, loff_t offset, loff_t end);
    +extern int vmtruncate_file_range(struct file *file, loff_t offset, loff_t end);

    int truncate_inode_page(struct address_space *mapping, struct page *page);
    int generic_error_remove_page(struct address_space *mapping, struct page *page);
    diff --git a/mm/madvise.c b/mm/madvise.c
    index 74bf193..3a281b7 100644
    --- a/mm/madvise.c
    +++ b/mm/madvise.c
    @@ -194,7 +194,7 @@ static long madvise_remove(struct vm_area_struct *vma,
    struct vm_area_struct **prev,
    unsigned long start, unsigned long end)
    {
    - struct address_space *mapping;
    + struct file *file;
    loff_t offset, endoff;
    int error;

    @@ -211,7 +211,7 @@ static long madvise_remove(struct vm_area_struct *vma,
    if ((vma->vm_flags & (VM_SHARED|VM_WRITE)) != (VM_SHARED|VM_WRITE))
    return -EACCES;

    - mapping = vma->vm_file->f_mapping;
    + file = vma->vm_file;

    offset = (loff_t)(start - vma->vm_start)
    + ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
    @@ -220,7 +220,7 @@ static long madvise_remove(struct vm_area_struct *vma,

    /* vmtruncate_range needs to take i_mutex */
    up_read(&current->mm->mmap_sem);
    - error = vmtruncate_range(mapping->host, offset, endoff);
    + error = vmtruncate_file_range(file, offset, endoff);
    down_read(&current->mm->mmap_sem);
    return error;
    }
    diff --git a/mm/shmem.c b/mm/shmem.c
    index 90c835b..b435da8 100644
    --- a/mm/shmem.c
    +++ b/mm/shmem.c
    @@ -1465,6 +1465,7 @@ static long shmem_fallocate(struct file *file, int mode,
    loff_t offset, loff_t len)
    {
    struct inode *inode = file->f_path.dentry->d_inode;
    + struct address_space *mapping = file->f_mapping;
    pgoff_t start = offset >> PAGE_CACHE_SHIFT;
    pgoff_t end = DIV_ROUND_UP((offset + len), PAGE_CACHE_SIZE);
    pgoff_t index = start;
    @@ -1476,6 +1477,12 @@ static long shmem_fallocate(struct file *file, int mode,
    return -ETXTBSY;

    mutex_lock(&inode->i_mutex);
    +
    + if (mapping) {
    + inode_dio_wait(mapping->host);
    + unmap_mapping_range(mapping, offset, len, 1);
    + }
    +
    i_size = inode->i_size;
    if (mode & FALLOC_FL_PUNCH_HOLE) {
    if (!(offset > i_size || (end << PAGE_CACHE_SHIFT) > i_size))
    @@ -1507,6 +1514,10 @@ static long shmem_fallocate(struct file *file, int mode,
    if (!(mode & FALLOC_FL_KEEP_SIZE) && (index << PAGE_CACHE_SHIFT) > i_size)
    i_size_write(inode, index << PAGE_CACHE_SHIFT);

    + /* unmap again to remove racily COWed private pages */
    + if (mapping)
    + unmap_mapping_range(mapping, offset, len, 1);
    +
    goto unlock;

    undo:
    @@ -2381,7 +2392,6 @@ static const struct file_operations shmem_file_operations = {

    static const struct inode_operations shmem_inode_operations = {
    .setattr = shmem_setattr,
    - .truncate_range = shmem_truncate_range,
    #ifdef CONFIG_TMPFS_XATTR
    .setxattr = shmem_setxattr,
    .getxattr = shmem_getxattr,
    diff --git a/mm/truncate.c b/mm/truncate.c
    index 632b15e..5a7ddda 100644
    --- a/mm/truncate.c
    +++ b/mm/truncate.c
    @@ -20,6 +20,7 @@
    #include <linux/buffer_head.h> /* grr. try_to_release_page,
    do_invalidatepage */
    #include <linux/cleancache.h>
    +#include <linux/falloc.h>
    #include "internal.h"


    @@ -602,27 +603,14 @@ int vmtruncate(struct inode *inode, loff_t newsize)
    }
    EXPORT_SYMBOL(vmtruncate);

    -int vmtruncate_range(struct inode *inode, loff_t lstart, loff_t lend)
    +int vmtruncate_file_range(struct file *file, loff_t lstart, loff_t lend)
    {
    - struct address_space *mapping = inode->i_mapping;
    loff_t holebegin = round_up(lstart, PAGE_SIZE);
    loff_t holelen = 1 + lend - holebegin;

    - /*
    - * If the underlying filesystem is not going to provide
    - * a way to truncate a range of blocks (punch a hole) -
    - * we should return failure right now.
    - */
    - if (!inode->i_op->truncate_range)
    + if (!file->f_op->fallocate)
    return -ENOSYS;

    - mutex_lock(&inode->i_mutex);
    - inode_dio_wait(inode);
    - unmap_mapping_range(mapping, holebegin, holelen, 1);
    - inode->i_op->truncate_range(inode, lstart, lend);
    - /* unmap again to remove racily COWed private pages */
    - unmap_mapping_range(mapping, holebegin, holelen, 1);
    - mutex_unlock(&inode->i_mutex);
    -
    - return 0;
    + return do_fallocate(file, FALLOC_FL_KEEP_SIZE|FALLOC_FL_PUNCH_HOLE,
    + holebegin, holelen);
    }

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