On 07.05.20 22:53, Vivek Goyal wrote: > On Wed, May 06, 2020 at 05:32:58PM +0200, Max Reitz wrote: >> Hi, >> >> This RFC consists of two patch series, one for virtiofsd (i.e., to be >> applied to the qemu repo), and one for Linux. >> >> The problem it wants to solve is that virtiofsd just passes through the >> stat.st_ino value from the host to the guest, without taking stat.st_dev >> into account. Therefore, it is generally impossible to uniquely >> identify nodes in the guest by their st_dev/st_ino combinations. >> >> One way to fix this would be to derive some algorithm to derive a unique >> st_ino value from the st_dev/st_ino combination on the host, but this is >> not always possible. >> >> So what this series does it basically passing through st_dev alongside >> st_ino: We can let the guest create auto-mounted submounts for every >> host mount point, so that they get their own dedicated st_dev. This is >> similar to what NFS does with the crossmnt option. >> >> Announcing submounts to the guest (the FUSE client) is done by the FUSE >> server (virtiofsd) of setting st_rdev to a non-zero value (e.g. st_dev) >> for every mount point. >> >> In this version here, duplicate mounts on the host (same st_dev) will >> not necessarily have the same st_dev in the guest. That would be more >> complicated to implement, and there is probably no real need to. > > Hi Max, > > What's duplicate mount. Is it two bind bounts created from same > filesystem.
For example; or the same filesystem from the same device twice (mount /dev/loop0 a; mount /dev/loop0 b). > So two bind mounts which have same st_dev on host, will appear to come > from two different devices in guest (different st_dev), right? Yes. Max
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