Messages in this thread | | | Date | Fri, 17 Sep 1999 14:17:40 -0700 (PDT) | From | (V. Ganesh) | Subject | Re: how does generic_file_read work with page_cache? |
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> From: "Peter J. Braam" <braam@cs.cmu.edu> > Date: Wed, 22 Sep 1999 03:39:07 +0000
[snip]
> - functions reading the page do a page_get -- but there is no page_put, > instead they call the un-understandable page_cache_release. > > Below in the snippet from generic_page read, the normal path does: > > get_page(page) > if all is well copy the data from the page > page_cache_release(page) > > But the latter is in fact __free_page(page) which is defined in > page_alloc.c and is very appropriately labeled as "You really aren't > expected to understand this". > > - What does that function do with the page? > - Who sets back the page count, which was increased by get_page? > - How can I operate with pages in a file system?
yeah, that is somewhat silly. it should have been put_page(page) rather than page_cache_release(page) if only for clarity. anyway, put_page is also #defined to be __free_page. it's __free_page which decrements the page count. if the count drops to zero, then __free_page really frees the page i.e. puts it back into the free page list, merging with buddy if possible, etc.
ganesh
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