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authorLouis Rilling <Louis.Rilling@kerlabs.com>2008-06-16 19:01:02 +0200
committerMark Fasheh <mfasheh@suse.com>2008-07-14 22:57:16 +0200
commit6d8344baee99402de58b5fa5dfea197242955c15 (patch)
tree6be890feb8063bdaac6efaff1044980cb76ee961 /fs/dlm
parentconfigfs: Fix deadlock with racing rmdir() and rename() (diff)
downloadlinux-6d8344baee99402de58b5fa5dfea197242955c15.tar.xz
linux-6d8344baee99402de58b5fa5dfea197242955c15.zip
configfs: Fix failing mkdir() making racing rmdir() fail
When fixing the rename() vs rmdir() deadlock, we stopped locking default groups' inodes in configfs_detach_prep(), letting racing mkdir() in default groups proceed concurrently. This enables races like below happen, which leads to a failing mkdir() making rmdir() fail, despite the group to remove having no user-created directory under it in the end. process A: process B: /* PWD=A/B */ mkdir("C") make_item("C") attach_group("C") rmdir("A") detach_prep("A") detach_prep("B") error because of "C" return -ENOTEMPTY attach_group("C/D") error (eg -ENOMEM) return -ENOMEM This patch prevents such scenarii by making rmdir() wait as long as detach_prep() fails because a racing mkdir() is in the middle of attach_group(). To achieve this, mkdir() sets a flag CONFIGFS_USET_IN_MKDIR in parent's configfs_dirent before calling attach_group(), and clears the flag once attach_group() is done. detach_prep() fails with -EAGAIN whenever the flag is hit and returns the guilty inode's mutex so that rmdir() can wait on it. Signed-off-by: Louis Rilling <Louis.Rilling@kerlabs.com> Signed-off-by: Joel Becker <joel.becker@oracle.com>
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