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authorecashin@coraid.com <ecashin@coraid.com>2005-04-19 01:00:21 -0400
committerGreg KH <greg@press.kroah.org>2005-04-19 01:00:21 -0400
commite3b7df65e089f143b9228472b80fb96c495fb634 (patch)
treea2366a9a09aaa9063b3b4e41eab747fc0c8b29a5 /Documentation
parentd098840e37468fdd0143d8bcfe86bc53627bf96e (diff)
[PATCH] aoe 9/12: add note about the need for deadlock-free sk_buff allocation
add note about the need for deadlock-free sk_buff allocation Signed-off-by: Ed L. Cashin <ecashin@coraid.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
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1There is a potential for deadlock when allocating a struct sk_buff for
2data that needs to be written out to aoe storage. If the data is
3being written from a dirty page in order to free that page, and if
4there are no other pages available, then deadlock may occur when a
5free page is needed for the sk_buff allocation. This situation has
6not been observed, but it would be nice to eliminate any potential for
7deadlock under memory pressure.
8
9Because ATA over Ethernet is not fragmented by the kernel's IP code,
10the destructore member of the struct sk_buff is available to the aoe
11driver. By using a mempool for allocating all but the first few
12sk_buffs, and by registering a destructor, we should be able to
13efficiently allocate sk_buffs without introducing any potential for
14deadlock.