Is there a difference between how ext2 allocates block between inode's indirect blocks and data blocks. On Fri, Dec 19, 2008 at 8:59 PM, Peter Teoh <htmldeveloper@xxxxxxxxx> wrote: > On Fri, Dec 19, 2008 at 7:18 PM, Rohit Sharma <imreckless@xxxxxxxxx> wrote: >> 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. >> >> > > http://lwn.net/Articles/81357/ ===> from here, we deduced that it > should be done at every new block request level, and not at the file > level. This is because when file level request is initiated, the > first thing is see if any existing block can be reused or not, before > allocating new block (which then comes with reservation features - to > ensure contiguity of datablocks). > > > -- > 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
