• Amit Arora's avatar
    sys_fallocate() implementation on i386, x86_64 and powerpc · 97ac7350
    Amit Arora authored
    fallocate() is a new system call being proposed here which will allow
    applications to preallocate space to any file(s) in a file system.
    Each file system implementation that wants to use this feature will need
    to support an inode operation called ->fallocate().
    Applications can use this feature to avoid fragmentation to certain
    level and thus get faster access speed. With preallocation, applications
    also get a guarantee of space for particular file(s) - even if later the
    the system becomes full.
    
    Currently, glibc provides an interface called posix_fallocate() which
    can be used for similar cause. Though this has the advantage of working
    on all file systems, but it is quite slow (since it writes zeroes to
    each block that has to be preallocated). Without a doubt, file systems
    can do this more efficiently within the kernel, by implementing
    the proposed fallocate() system call. It is expected that
    posix_fallocate() will be modified to call this new system call first
    and incase the kernel/filesystem does not implement it, it should fall
    back to the current implementation of writing zeroes to the new blocks.
    ToDos:
    1. Implementation on other architectures (other than i386, x86_64,
       and ppc). Patches for s390(x) and ia64 are already available from
       previous posts, but it was decided that they should be added later
       once fallocate is in the mainline. Hence not including those patches
       in this take.
    2. Changes to glibc,
       a) to support fallocate() system call
       b) to make posix_fallocate() and posix_fallocate64() call fallocate()
    Signed-off-by: default avatarAmit Arora <aarora@in.ibm.com>
    97ac7350
falloc.h 126 Bytes