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Change rangelock handling in FreeBSD's zfs_getpages() #16643

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Change rangelock handling in FreeBSD's zfs_getpages() #16643

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Commits on Oct 13, 2024

  1. Fix a potential page leak in mappedread_sf() 

    mappedread_sf() may allocate pages; if it fails to populate a page
can't free it, it needs to ensure that it's placed into a page queue,
otherwise it can't be reclaimed until the vnode is destroyed.

I think this is quite unlikely to happen in practice, it was noticed by
code inspection.

Signed-off-by: Mark Johnston <markj@FreeBSD.org>
    @markjdb
    markjdb committed Oct 13, 2024
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  2. Grab the rangelock unconditionally in zfs_getpages() 

    As a deadlock avoidance measure, zfs_getpages() would only try to
acquire a rangelock, falling back to a single-page read if this was not
possible.  However, this is incompatible with direct I/O.

Instead, release the busy lock before trying to acquire the rangelock in
blocking mode.  This means that it's possible for the page to be
replaced, so we have to re-lookup.

Signed-off-by: Mark Johnston <markj@FreeBSD.org>
    @markjdb
    markjdb committed Oct 13, 2024
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