On Fri, Dec 19, 2008 at 3:05 PM, Peter Teoh <htmldeveloper@xxxxxxxxx> wrote: > On Fri, Dec 19, 2008 at 3:42 PM, Rohit Sharma <imreckless@xxxxxxxxx> wrote: >> On Fri, Dec 19, 2008 at 4:09 AM, Jan Kara <jack@xxxxxxx> wrote: >>>> On Fri, Dec 19, 2008 at 12:12 AM, Rohit Sharma <imreckless@xxxxxxxxx> wrote: >>>> > How does ext2 allocate blocks for directory. >>>> > >>>> > ext2_mkdir calls ext2_make_empty >>>> > >>>> > ext2_make_empty calls __ext2_write_begin >>>> > >>>> > __ ext2_write_begin calls block_write_begin >>>> > >>>> > my query is that how does this function allocates blocks for directories. ?? >>>> > >>>> >>>> Does ext2 uses ext2_get_block to allocate blocks for both files and >>>> directories. ?? >>> Yes, exactly. Ext2 (unlike ext3 or ext4) treats directories the same >>> ways as ordinary files and thus ext2_get_block is used for block >>> allocation. >>> >> >> Can i modify this function to restrict allocation of blocks >> to a particular block group ? >> >> Like i want that my abc.txt file should be in block group 5 suppose, then >> what should i do? >> > > I think this can be done. Or is done in the kernel source in several > ways (indirectly). > > 1. ext2_find_goal()-->this will look for the best new block. when > searching, it will try to find the block to be allocated to follow the > one last allocated in the file, so as to maintain storage contiguity. > > 2. looking into fs/ext2/balloc.c: ext2_try_to_allocate(), there is a > argument called group_goal, whose purpose is to specify the goal block > group, and the algorithm will start searching from the group specified > (look for "start=grp_goal"). Of course, if search is in vain it will > proceed to other block group, which u don't want ....so may be can > customize from here. > > Not sure if I am right? > When we create new file, do we use reservation window to allocate blocks or we use reservation window every time we need a new data blocks for file. > -- > Regards, > Peter Teoh > > Ernest Hemingway - "Never mistake motion for action." > -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ
