mvs 178729573e Modify the behavior of tmpfs limitations. Keep the global memory limit ...

of all tmpfs instances, however each instance mounted with '-s' option
decreases available limit by given value. This value can't be greater
than available space. The instance mounted with  with '-s' option
consumes it's own limit and does no impact to other tmpfs instances. The
instances mounted without '-s' option share all available limit and do
not affect on instances mounted with '-s'. Now it is impossible to mount
instance with '-s' option if passed value is greater than available
limit.

Tested with dbp(1) by kirill, ok mpi

For example, this machine has 2G of RAM, so tmpfs is limited with 1G.
Please note, the +- 1Mb depends of how 'dd', 'df' and 'mount_tmpfs'
expose the sizes.

# mount_tmpfs tmpfs /mnt/t0
# mount_tmpfs tmpfs /mnt/t1
# mount_tmpfs -s 720M tmpfs /mnt/t2

# df -t tmpfs -h
Filesystem     Size    Used   Avail Capacity  Mounted on
tmpfs          257M      0B    257M     0%    /mnt/t0
tmpfs          257M      0B    257M     0%    /mnt/t1
tmpfs          720M    4.0K    720M     1%    /mnt/t2

# dd if=/dev/zero of=/mnt/t0/f0 bs=1M count=256
# df -t tmpfs -h
Filesystem     Size    Used   Avail Capacity  Mounted on
tmpfs          257M    256M    560K   100%    /mnt/t0
tmpfs          560K      0B    560K     0%    /mnt/t1
tmpfs          720M    4.0K    720M     1%    /mnt/t2

# mount_tmpfs -s 1M tmpfs /mnt/t3
mount_tmpfs: tmpfs on /mnt/t3: Invalid argument

# mount_tmpfs -s 1K tmpfs /mnt/t3
# df -t tmpfs -h
Filesystem     Size    Used   Avail Capacity  Mounted on
tmpfs          257M    256M    556K   100%    /mnt/t0
tmpfs          556K      0B    556K     0%    /mnt/t1
tmpfs          720M    4.0K    720M     1%    /mnt/t2
tmpfs          4.0K    4.0K      0B   100%    /mnt/t3

# mount_tmpfs tmpfs /mnt/t3
# df -t tmpfs -h
Filesystem     Size    Used   Avail Capacity  Mounted on
tmpfs          257M    256M    560K   100%    /mnt/t0
tmpfs          560K      0B    560K     0%    /mnt/t1
tmpfs          720M    4.0K    720M     1%    /mnt/t2
tmpfs          560K      0B    560K     0%    /mnt/t3

# dd if=/dev/zero of=/mnt/t2/f0 bs=1M count=128
# df -t tmpfs -h
Filesystem     Size    Used   Avail Capacity  Mounted on
tmpfs          257M    256M    560K   100%    /mnt/t0
tmpfs          560K      0B    560K     0%    /mnt/t1
tmpfs          720M    128M    592M    18%    /mnt/t2

# rm -rf /mnt/t0/f0
# df -t tmpfs -h
Filesystem     Size    Used   Avail Capacity  Mounted on
tmpfs          257M      0B    257M     0%    /mnt/t0
tmpfs          257M      0B    257M     0%    /mnt/t1
tmpfs          720M    128M    592M    18%    /mnt/t2

# mount_tmpfs -s 128M tmpfs /mnt/t3
# df -t tmpfs -h
Filesystem     Size    Used   Avail Capacity  Mounted on
tmpfs          129M      0B    129M     0%    /mnt/t0
tmpfs          129M      0B    129M     0%    /mnt/t1
tmpfs          720M    128M    592M    18%    /mnt/t2
tmpfs          128M    4.0K    128M     1%    /mnt/t3

# dd if=/dev/zero of=/mnt/t0/f0 bs=1M count=32
# dd if=/dev/zero of=/mnt/t1/f0 bs=1M count=64
# df -t tmpfs -h
Filesystem     Size    Used   Avail Capacity  Mounted on
tmpfs          193M   32.0M    161M    17%    /mnt/t0
tmpfs          225M   64.0M    161M    29%    /mnt/t1
tmpfs          720M    128M    592M    18%    /mnt/t2

# mount_tmpfs -s 128M tmpfs /mnt/t3
# df -t tmpfs -h
Filesystem     Size    Used   Avail Capacity  Mounted on
tmpfs         64.5M   32.0M   32.5M    50%    /mnt/t0
tmpfs         96.5M   64.0M   32.5M    67%    /mnt/t1
tmpfs          720M    128M    592M    18%    /mnt/t2
tmpfs          128M    4.0K    128M     1%    /mnt/t3

# dd if=/dev/zero of=/mnt/t1/f1 bs=1M count=64
# df -t tmpfs -h
Filesystem     Size    Used   Avail Capacity  Mounted on
tmpfs          129M   32.0M   96.5M    25%    /mnt/t0
tmpfs          225M    128M   96.5M    58%    /mnt/t1
tmpfs          720M    128M    592M    18%    /mnt/t2

# mount_tmpfs -s 128M tmpfs /mnt/t3
mount_tmpfs: tmpfs on /mnt/t3: Invalid argument
# mount_tmpfs -s 96M tmpfs /mnt/t3
# df -t tmpfs -h
Filesystem     Size    Used   Avail Capacity  Mounted on
tmpfs         32.5M   32.0M    560K    99%    /mnt/t0
tmpfs          129M    128M    560K   100%    /mnt/t1
tmpfs          720M    128M    592M    18%    /mnt/t2
tmpfs         96.0M    4.0K   96.0M     1%    /mnt/t3

# mount_tmpfs tmpfs /mnt/t4
# mount_tmpfs tmpfs /mnt/t5
# mount_tmpfs tmpfs /mnt/t6
# mount_tmpfs tmpfs /mnt/t7
# mount_tmpfs tmpfs /mnt/t8
# df -t tmpfs -h
Filesystem     Size    Used   Avail Capacity  Mounted on
tmpfs         32.5M   32.0M    560K    99%    /mnt/t0
tmpfs          129M    128M    560K   100%    /mnt/t1
tmpfs          720M    128M    592M    18%    /mnt/t2
tmpfs         96.0M    4.0K   96.0M     1%    /mnt/t3
tmpfs          560K      0B    560K     0%    /mnt/t4
tmpfs          560K      0B    560K     0%    /mnt/t5
tmpfs          560K      0B    560K     0%    /mnt/t6
tmpfs          560K      0B    560K     0%    /mnt/t7
tmpfs          560K      0B    560K     0%    /mnt/t8

2025-11-21 09:49:33 +00:00

..

tmpfs_fifoops.c

…

tmpfs_mem.c

Modify the behavior of tmpfs limitations. Keep the global memory limit

2025-11-21 09:49:33 +00:00

tmpfs_specops.c

…

tmpfs_subr.c

…

tmpfs_vfsops.c

Modify the behavior of tmpfs limitations. Keep the global memory limit

2025-11-21 09:49:33 +00:00

tmpfs_vnops.c

…

tmpfs_vnops.h

…

tmpfs.h

…