[lkml]   [2000]   [Oct]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: page->mapping == 0
    Paul Mackerras wrote:
    > I am not any kind of expert on the page cache but it seems to me that
    > maybe after locking the page we should check if it is still the page
    > we want (i.e. page->mapping and page->index are still correct), and go
    > back and look up the page again if not. Presumably there will be
    > quite a few places besides do_generic_file_read where that check would
    > be needed also.

    I'm getting at least some kind of clue about the page cache, though I
    don't claim to be an expert. You've pointed out how the operation of
    becoming a reader on a page can fail because the page disappears while
    you're waiting. That's an error, right? It's the result of a user
    space race, which in turn is the result of parallel processes doing
    nonatomic file operations with no synchronization. It sounds like
    bailing out of the file_read if the page turns out to be unmapped after
    the lock is the right thing to do, at least for a quick fix.

    There actually aren't that many places where lock_page is called:;i=lock_page

    Maybe lock_page needs to return an error code.

    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to
    Please read the FAQ at

     \ /
      Last update: 2005-03-22 12:45    [W:0.099 / U:3.196 seconds]
    ©2003-2017 Jasper Spaans. hosted at Digital OceanAdvertise on this site