On Wed, 2005-07-20 at 20:14 -0700, Badari Pulavarty wrote: > Nir Tzachar wrote: > > > hello list. > > > > can someone please explain the exact semantics the get_block_t function > > (which is passed to mpage_readpage(s)) should implement?? > > i could not find any documentation, and existing code kind of baffled > > me... > > > > my current understanding goes like this: > > if the block is present, call map_bh on the bh, with the physical block > > number. > > else, if "create" is set, allocate a new block for the inode, and again > > update the new physical block number. > > > > is this all?? > > > > thanks. > > > > For a given file offset, get_block() function is supposed to return the > physical disk block# of the block. (and size of the block). If "create" > is one, it needs to allocate the block (if it doesn't already exist). > Makes sense ?
from fs.h:
typedef int (get_block_t)(struct inode *inode, sector_t iblock,
struct buffer_head *bh_result, int create);
so, iblock is the block number in the file, or the offset in the file??
furthermore, what set_buffer_mapped (used in map_bh) does?? i could not
find it's definition anywhere??
about create, "allocate a block" means just deciding which block should
be allocated, update the fs control structures, and return that block #,
right??
> Thanks,
> Badari
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Nir Tzachar.
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