[PATCH 0/3] ext4: Handle different max offsets for bitmap & extent-based files

[Eric Sandeen <sandeen@redhat.com>]

Basic approach: have both ext4_max_bitmap_size() and ext4_max_size()
functions to compute max offsets for both types of formats.

Use vfs sb->s_maxbytes for the "native" maxbytes, i.e. extent-format files.

Put the smaller bitmap limit in a new sbi->s_bitmap_maxbytes in the ext4
superblock info structure.

Catch bitmap files in ext4_file_write() and ext4_setattr() to limit
extending writes, llseeks, and truncates to too-large offsets which the
VFS let through due to the extent-format maxbytes.  On write, allow
writes up to the max, but then stop, by using iov_shorten() to limit the
size of the write to the maximum.

3 patches follow:

ext4_two_maxbytes_functions.patch - differentiate the maxbytes f'ns
ext4_bitmap_maxbytes_vfs.patch - export iov_shorten from kernel
ext4_bitmap_maxbytes.patch - store, and limit to, bitmap_maxbytes

Comments?

Thanks,
-Eric