From: Miklos Szeredi <miklos@szeredi.hu>
Date: Tue, 11 Apr 2006 19:14:26 +0000 (+0200)
Subject: [fuse] fix deadlock between fuse_put_super() and request_end()
X-Git-Tag: v2.6.17-rc2~73^2~3
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=73ce8355c243a434524a34c05cc417dd0467996e;p=pandora-kernel.git

[fuse] fix deadlock between fuse_put_super() and request_end()

A deadlock was possible, when the last reference to the superblock was
held due to a background request containing a file reference.

Releasing the file would release the vfsmount which in turn would
release the superblock.  Since sbput_sem is held during the fput() and
fuse_put_super() tries to acquire this same semaphore, a deadlock
results.

The chosen soltuion is to get rid of sbput_sem, and instead use the
spinlock to ensure the referenced inodes/file are released only once.
Since the actual release may sleep, defer these outside the locked
region, but using local variables instead of the structure members.

This is a much more rubust solution.

Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
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