kernel/git/stable/linux.git/Documentation/filesystems, branch linux-2.6.27.y

doc: add the documentation for mpol=local

2010-04-01T22:52:28+00:00

commit 5574169613b40b85d6f4c67208fa4846b897a0a1 upstream. commit 3f226aa1c (mempolicy: support mpol=local tmpfs mount option) added new mpol=local mount option. but it didn't add a documentation. This patch does it. Signed-off-by: KOSAKI Motohiro Cc: Ravikiran Thirumalai Cc: Christoph Lameter Cc: Mel Gorman Acked-by: Lee Schermerhorn Cc: Hugh Dickins Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

ext4: Add fine print for the 32000 subdirectory limit

2009-06-12T03:01:46+00:00

(cherry picked from commit 722bde6875bfb49a0c84e5601eb82dd7ac02d27c) Some poeple are reading the ext4 feature list too literally and create dubious test cases involving very long filenames and 1k blocksize and then complain when they run into an htree-imposed limit. So add fine print to the "fix 32000 subdirectory limit" ext4 feature. Signed-off-by: "Theodore Ts'o" Signed-off-by: Greg Kroah-Hartman

mm: close page_mkwrite races

2009-05-20T05:20:09+00:00

commit b827e496c893de0c0f142abfaeb8730a2fd6b37f upstream mm: close page_mkwrite races Change page_mkwrite to allow implementations to return with the page locked, and also change it's callers (in page fault paths) to hold the lock until the page is marked dirty. This allows the filesystem to have full control of page dirtying events coming from the VM. Rather than simply hold the page locked over the page_mkwrite call, we call page_mkwrite with the page unlocked and allow callers to return with it locked, so filesystems can avoid LOR conditions with page lock. The problem with the current scheme is this: a filesystem that wants to associate some metadata with a page as long as the page is dirty, will perform this manipulation in its ->page_mkwrite. It currently then must return with the page unlocked and may not hold any other locks (according to existing page_mkwrite convention). In this window, the VM could write out the page, clearing page-dirty. The filesystem has no good way to detect that a dirty pte is about to be attached, so it will happily write out the page, at which point, the filesystem may manipulate the metadata to reflect that the page is no longer dirty. It is not always possible to perform the required metadata manipulation in ->set_page_dirty, because that function cannot block or fail. The filesystem may need to allocate some data structure, for example. And the VM cannot mark the pte dirty before page_mkwrite, because page_mkwrite is allowed to fail, so we must not allow any window where the page could be written to if page_mkwrite does fail. This solution of holding the page locked over the 3 critical operations (page_mkwrite, setting the pte dirty, and finally setting the page dirty) closes out races nicely, preventing page cleaning for writeout being initiated in that window. This provides the filesystem with a strong synchronisation against the VM here. - Sage needs this race closed for ceph filesystem. - Trond for NFS (http://bugzilla.kernel.org/show_bug.cgi?id=12913). - I need it for fsblock. - I suspect other filesystems may need it too (eg. btrfs). - I have converted buffer.c to the new locking. Even simple block allocation under dirty pages might be susceptible to i_size changing under partial page at the end of file (we also have a buffer.c-side problem here, but it cannot be fixed properly without this patch). - Other filesystems (eg. NFS, maybe btrfs) will need to change their page_mkwrite functions themselves. [ This also moves page_mkwrite another step closer to fault, which should eventually allow page_mkwrite to be moved into ->fault, and thus avoiding a filesystem calldown and page lock/unlock cycle in __do_fault. ] [akpm@linux-foundation.org: fix derefs of NULL ->mapping] Cc: Sage Weil Cc: Trond Myklebust Signed-off-by: Nick Piggin Cc: Valdis Kletnieks Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

mm: page_mkwrite change prototype to match fault

2009-05-20T05:20:09+00:00

commit c2ec175c39f62949438354f603f4aa170846aabb upstream mm: page_mkwrite change prototype to match fault Change the page_mkwrite prototype to take a struct vm_fault, and return VM_FAULT_xxx flags. There should be no functional change. This makes it possible to return much more detailed error information to the VM (and also can provide more information eg. virtual_address to the driver, which might be important in some special cases). This is required for a subsequent fix. And will also make it easier to merge page_mkwrite() with fault() in future. Signed-off-by: Nick Piggin Cc: Chris Mason Cc: Trond Myklebust Cc: Miklos Szeredi Cc: Steven Whitehouse Cc: Mark Fasheh Cc: Joel Becker Cc: Artem Bityutskiy Cc: Felix Blyakher Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

PCI: return error on failure to read PCI ROMs

2009-02-12T17:31:10+00:00

commit 97c44836cdec1ea713a15d84098a1a908157e68f upstream. This patch makes the ROM reading code return an error to user space if the size of the ROM read is equal to 0. The patch also emits a warnings if the contents of the ROM are invalid, and documents the effects of the "enable" file on ROM reading. Signed-off-by: Timothy S. Nelson Acked-by: Alex Villacis-Lasso Signed-off-by: Jesse Barnes Signed-off-by: Greg Kroah-Hartman

epoll: introduce resource usage limits

2008-12-05T18:55:12+00:00

commit 7ef9964e6d1b911b78709f144000aacadd0ebc21 upstream. 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 Cc: Michael Kerrisk Cc: Cyrill Gorcunov Reported-by: Vegard Nossum Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

coredump_filter: add description of bit 4

2008-09-13T21:41:51+00:00

There is no description of bit 4 of coredump_filter in the documentation. This patch adds it. Signed-off-by: Hidehiro Kawai Cc: Roland McGrath Cc: Mel Gorman Acked-by: KOSAKI Motohiro Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

update Documentation/filesystems/Locking for 2.6.27 changes

2008-09-09T18:51:15+00:00

In the 2.6.27 circle ->fasync lost the BKL, and the last remaining ->open variant that takes the BKL is also gone. ->get_sb and ->kill_sb didn't have BKL forever, so updated the entries while we're at that. Signed-off-by: Christoph Hellwig Signed-off-by: Linus Torvalds

ipc: document the new auto_msgmni proc file

2008-09-03T02:21:39+00:00

Update Documentation/filesystems/proc.txt: it describes the file auto_msgmni intoduced to enable/disable msgmni automatic recomputing upon memory add/remove (see thread http://lkml.org/lkml/2008/7/4/27). Also added a description for msgmni (this filex is only listed in Documentation/sysctl/kernel.txt). Signed-off-by: Nadia Derbey Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

NTFS: update homepage

2008-09-03T02:21:37+00:00

Update the location of the NTFS homepage in several files. Signed-off-by: Adrian Bunk Cc: Jeff Garzik Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds