WSL2-Linux-Kernel/Documentation/filesystems
Davide Libenzi 7ef9964e6d epoll: introduce resource usage limits
It has been thought that the per-user file descriptors limit would also
limit the resources that a normal user can request via the epoll
interface.  Vegard Nossum reported a very simple program (a modified
version attached) that can make a normal user to request a pretty large
amount of kernel memory, well within the its maximum number of fds.  To
solve such problem, default limits are now imposed, and /proc based
configuration has been introduced.  A new directory has been created,
named /proc/sys/fs/epoll/ and inside there, there are two configuration
points:

  max_user_instances = Maximum number of devices - per user

  max_user_watches   = Maximum number of "watched" fds - per user

The current default for "max_user_watches" limits the memory used by epoll
to store "watches", to 1/32 of the amount of the low RAM.  As example, a
256MB 32bit machine, will have "max_user_watches" set to roughly 90000.
That should be enough to not break existing heavy epoll users.  The
default value for "max_user_instances" is set to 128, that should be
enough too.

This also changes the userspace, because a new error code can now come out
from EPOLL_CTL_ADD (-ENOSPC).  The EMFILE from epoll_create() was already
listed, so that should be ok.

[akpm@linux-foundation.org: use get_current_user()]
Signed-off-by: Davide Libenzi <davidel@xmailserver.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: <stable@kernel.org>
Cc: Cyrill Gorcunov <gorcunov@gmail.com>
Reported-by: Vegard Nossum <vegardno@ifi.uio.no>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-12-01 19:55:24 -08:00
..
configfs docsrc: build Documentation/ sources 2008-08-12 16:07:30 -07:00
00-INDEX Documentation: move rpc-cache.txt to filesystems/ 2008-04-11 13:20:52 -06:00
9p.txt 9p: add virtio transport 2007-10-23 13:47:31 -05:00
Exporting exportfs: update documentation 2007-10-22 08:13:21 -07:00
Locking fs: remove prepare_write/commit_write 2008-10-30 11:38:45 -07:00
adfs.txt Fix typos in /Documentation : 'U-Z' 2006-11-30 04:58:40 +01:00
affs.txt [PATCH] kernel Doc/ URL corrections 2005-11-22 09:14:30 -08:00
afs.txt [AFS]: Update the AFS fs documentation. 2007-04-26 15:57:43 -07:00
autofs4-mount-control.txt autofs4: device node ioctl documentation 2008-10-16 11:21:39 -07:00
automount-support.txt VFS: Unexport do_kern_mount() and clean up simple_pin_fs() 2006-06-09 09:34:16 -04:00
befs.txt Fix typos in Documentation/: 'Q'-'R' 2006-10-03 22:54:15 +02:00
bfs.txt remove mention of CONFIG_KMOD from documentation 2008-07-22 19:24:29 +10:00
cifs.txt
coda.txt
cramfs.txt
dentry-locking.txt [PATCH] VFS: split dentry locking documentation 2005-11-07 07:53:56 -08:00
directory-locking Documentation: Fix up docs still talking about i_sem 2007-05-24 10:16:17 -07:00
dlmfs.txt Fix typos in Documentation/: 'D'-'E' 2006-10-03 22:47:42 +02:00
dnotify.txt Documentation: move dnotify.txt to filesystems/ 2008-02-07 08:42:17 -08:00
ecryptfs.txt eCryptfs: Move ecryptfs docs into Documentation/filesystems/ 2007-07-17 10:23:08 -07:00
ext2.txt Fix typos in Documentation/: 'N'-'P' 2006-10-03 22:52:05 +02:00
ext3.txt ext3: add an option to control error handling on file data 2008-10-20 08:52:37 -07:00
ext4.txt ext4: Update Documentation/filesystems/ext4.txt 2008-10-17 09:15:14 -04:00
fiemap.txt vfs: vfs-level fiemap interface 2008-10-08 19:44:18 -04:00
files.txt Documentation/filesystems/files.txt: remove rcuref_inc_lf() reverences 2007-10-20 01:47:49 +02:00
fuse.txt [PATCH] fuse: fix typo 2006-12-30 10:56:45 -08:00
gfs2-glocks.txt [GFS2] Glock documentation 2008-06-27 09:39:53 +01:00
gfs2.txt [GFS2] Update documentation 2006-04-25 15:44:04 -04:00
hfs.txt
hfsplus.txt Documentation: document HFSPlus 2007-07-31 15:39:38 -07:00
hpfs.txt misc doc and kconfig typos 2007-05-09 08:58:15 +02:00
inotify.txt [PATCH] inotify (5/5): update kernel documentation 2006-06-20 05:25:19 -04:00
isofs.txt isofs: implement dmode option 2008-02-08 09:22:38 -08:00
jfs.txt JFS: document uid, gid, and umask mount options in jfs.txt 2007-03-09 10:27:31 -06:00
locks.txt Documentation: move locks.txt in filesystems/ 2007-10-09 18:32:45 -04:00
mandatory-locking.txt locks: add warning about mandatory locking races 2007-10-09 18:32:45 -04:00
ncpfs.txt
nfs-rdma.txt nfs: rewrap NFS/RDMA documentation to 80 lines 2008-06-30 15:24:43 -04:00
nfsroot.txt doc: typo in Documentation/filesystems/nfsroot.txt 2008-10-16 11:21:31 -07:00
ntfs.txt NTFS: update homepage 2008-09-02 19:21:37 -07:00
ocfs2.txt ocfs2: Small documentation update 2008-12-01 14:46:49 -08:00
omfs.txt omfs: add filesystem documentation 2008-07-26 12:00:05 -07:00
porting iget: remove iget() and the read_inode() super op as being obsolete 2008-02-07 08:42:29 -08:00
proc.txt epoll: introduce resource usage limits 2008-12-01 19:55:24 -08:00
quota.txt quota: documentation for sending "below quota" messages via netlink and tiny doc update 2008-08-12 16:07:27 -07:00
ramfs-rootfs-initramfs.txt Trivial Documentation/filesystems/ramfs-rootfs-initramfs.txt fix 2008-11-30 11:40:56 -08:00
relay.txt relay: add buffer-only channels; useful for early logging 2008-07-26 12:00:04 -07:00
romfs.txt
rpc-cache.txt Documentation: move rpc-cache.txt to filesystems/ 2008-04-11 13:20:52 -06:00
seq_file.txt Document seq_path_root() 2008-04-25 11:56:37 -06:00
sharedsubtree.txt Documentation: move sharedsubtrees.txt to filesystems/ 2008-02-07 08:42:17 -08:00
smbfs.txt
spufs.txt Fix typos in /Documentation : 'U-Z' 2006-11-30 04:58:40 +01:00
sysfs-pci.txt x86: PAT export resource_wc in pci sysfs 2008-06-12 10:12:42 +02:00
sysfs.txt sysfs: add /sys/dev/{char,block} to lookup sysfs path by major:minor 2008-07-21 21:54:40 -07:00
sysv-fs.txt [PATCH] fs/sysv/: doc cleanup 2006-12-07 08:39:44 -08:00
tmpfs.txt mempolicy: update NUMA memory policy documentation 2008-04-28 08:58:19 -07:00
ubifs.txt UBIFS: add no_chk_data_crc mount option 2008-09-30 11:12:56 +03:00
udf.txt [PATCH] Update udf documentation to reflect current state of read/write support 2006-11-16 11:43:38 -08:00
ufs.txt [PATCH] ufs2 write: mount as rw 2007-02-12 09:48:40 -08:00
vfat.txt fat: Fix ATTR_RO for directory 2008-11-06 15:41:21 -08:00
vfs.txt fs: remove prepare_write/commit_write 2008-10-30 11:38:45 -07:00
xfs.txt [XFS] Update XFS documentation for noikeep/ikeep. 2008-04-18 12:18:42 +10:00
xip.txt DOC: update xip method info 2008-11-12 17:17:17 -08:00