Change rangelock handling in FreeBSD's zfs_getpages() #16643
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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>
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>
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Unconditionally hold the rangelock in zfs_getpages().
Motivation and Context
This is reportedly required for direct I/O support on FreeBSD.
Description
This change modifies zfs_getpages() to uncondtionally acquire the rangelock. To avoid a deadlock, we may need to drop a page busy lock and allocate a new page later on.
How Has This Been Tested?
Smoke testing on FreeBSD.
Types of changes
Checklist:
Signed-off-by.