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    Subject[PATCH 03/11] ext2: Allocate space for mmaped file on page fault
    Date
    So far we've allocated space at ->writepage() time. This has the disadvantage
    that when we hit ENOSPC or other error, we cannot do much - either throw
    away the data or keep the page indefinitely (and loose the data on reboot).
    So allocate space already when a page is faulted in.

    Signed-off-by: Jan Kara <jack@suse.cz>
    ---
    fs/ext2/file.c | 26 +++++++++++++++++++++++++-
    fs/ext2/inode.c | 1 +
    2 files changed, 26 insertions(+), 1 deletions(-)

    diff --git a/fs/ext2/file.c b/fs/ext2/file.c
    index 2b9e47d..d0a5f13 100644
    --- a/fs/ext2/file.c
    +++ b/fs/ext2/file.c
    @@ -19,6 +19,8 @@
    */

    #include <linux/time.h>
    +#include <linux/mm.h>
    +#include <linux/buffer_head.h>
    #include "ext2.h"
    #include "xattr.h"
    #include "acl.h"
    @@ -38,6 +40,28 @@ static int ext2_release_file (struct inode * inode, struct file * filp)
    return 0;
    }

    +static int ext2_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
    +{
    + return block_page_mkwrite(vma, vmf, ext2_get_block);
    +}
    +
    +static struct vm_operations_struct ext2_file_vm_ops = {
    + .fault = filemap_fault,
    + .page_mkwrite = ext2_page_mkwrite,
    +};
    +
    +static int ext2_file_mmap(struct file *file, struct vm_area_struct *vma)
    +{
    + struct address_space *mapping = file->f_mapping;
    +
    + if (!mapping->a_ops->readpage)
    + return -ENOEXEC;
    + file_accessed(file);
    + vma->vm_ops = &ext2_file_vm_ops;
    + vma->vm_flags |= VM_CAN_NONLINEAR;
    + return 0;
    +}
    +
    /*
    * We have mostly NULL's here: the current defaults are ok for
    * the ext2 filesystem.
    @@ -52,7 +76,7 @@ const struct file_operations ext2_file_operations = {
    #ifdef CONFIG_COMPAT
    .compat_ioctl = ext2_compat_ioctl,
    #endif
    - .mmap = generic_file_mmap,
    + .mmap = ext2_file_mmap,
    .open = generic_file_open,
    .release = ext2_release_file,
    .fsync = simple_fsync,
    diff --git a/fs/ext2/inode.c b/fs/ext2/inode.c
    index 29ed682..3805b6b 100644
    --- a/fs/ext2/inode.c
    +++ b/fs/ext2/inode.c
    @@ -814,6 +814,7 @@ const struct address_space_operations ext2_aops = {
    .sync_page = block_sync_page,
    .write_begin = ext2_write_begin,
    .write_end = generic_write_end,
    + .extend_i_size = block_extend_i_size,
    .bmap = ext2_bmap,
    .direct_IO = ext2_direct_IO,
    .writepages = ext2_writepages,
    --
    1.6.0.2


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