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7a4dec5389
If sget() finds a matching superblock being set up, it'll grab an active reference to it and grab s_umount. That's fine - we'll wait for completion of foofs_get_sb() that way. However, if said foofs_get_sb() fails we'll end up holding the halfway-created superblock. deactivate_locked_super() called by foofs_get_sb() will just unlock the sucker since we are holding another active reference to it. What we need is a way to tell if superblock has been successfully set up. Unfortunately, neither ->s_root nor the check for MS_ACTIVE quite fit. Cheap and easy way, suitable for backport: new flag set by the (only) caller of ->get_sb(). If that flag isn't present by the time sget() grabbed s_umount on preexisting superblock it has found, it's seeing a stillborn and should just bury it with deactivate_locked_super() (and repeat the search). Longer term we want to set that flag in ->get_sb() instances (and check for it to distinguish between "sget() found us a live sb" and "sget() has allocated an sb, we need to set it up" in there, instead of checking ->s_root as we do now). Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Cc: stable@kernel.org |
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