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Date: Sat, 20 Dec 2008 00:31:30 +0530 From: "Rohit Sharma" <imreckless@...il.com> To: "Peter Teoh" <htmldeveloper@...il.com> Cc: "Jan Kara" <jack@...e.cz>, Kernelnewbies <kernelnewbies@...linux.org>, ext4 <linux-ext4@...r.kernel.org> Subject: Re: block allocation for ext2_mkdir I am not sure but ext2_alloc_blocks function in inode.c, allocate blocks for indirect blocks. On Sat, Dec 20, 2008 at 12:19 AM, Rohit Sharma <imreckless@...il.com> wrote: > 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@...il.com> wrote: >> On Fri, Dec 19, 2008 at 7:18 PM, Rohit Sharma <imreckless@...il.com> wrote: >>> On Fri, Dec 19, 2008 at 3:05 PM, Peter Teoh <htmldeveloper@...il.com> wrote: >>>> On Fri, Dec 19, 2008 at 3:42 PM, Rohit Sharma <imreckless@...il.com> wrote: >>>>> On Fri, Dec 19, 2008 at 4:09 AM, Jan Kara <jack@...e.cz> wrote: >>>>>>> On Fri, Dec 19, 2008 at 12:12 AM, Rohit Sharma <imreckless@...il.com> 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 the line "unsubscribe linux-ext4" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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