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authorJ. Bruce Fields <bfields@citi.umich.edu>2009-06-15 18:08:07 -0700
committerJ. Bruce Fields <bfields@citi.umich.edu>2009-06-15 18:08:07 -0700
commit7eef4091a653c243a87e5375c54504cc03bec4d8 (patch)
treef65b77f830b2c8f7d014512badfef5df0d591ee9 /Documentation/filesystems
parent0a93a47f042c459f0f46942c3a920e3c81878031 (diff)
parent07a2039b8eb0af4ff464efd3dfd95de5c02648c6 (diff)
Merge commit 'v2.6.30' into for-2.6.31
Diffstat (limited to 'Documentation/filesystems')
-rw-r--r--Documentation/filesystems/Locking24
-rw-r--r--Documentation/filesystems/caching/cachefiles.txt8
-rw-r--r--Documentation/filesystems/tmpfs.txt2
3 files changed, 21 insertions, 13 deletions
diff --git a/Documentation/filesystems/Locking b/Documentation/filesystems/Locking
index 76efe5b71d7..3120f8dd2c3 100644
--- a/Documentation/filesystems/Locking
+++ b/Documentation/filesystems/Locking
@@ -512,16 +512,24 @@ locking rules:
BKL mmap_sem PageLocked(page)
open: no yes
close: no yes
-fault: no yes
-page_mkwrite: no yes no
+fault: no yes can return with page locked
+page_mkwrite: no yes can return with page locked
access: no yes
- ->page_mkwrite() is called when a previously read-only page is
-about to become writeable. The file system is responsible for
-protecting against truncate races. Once appropriate action has been
-taking to lock out truncate, the page range should be verified to be
-within i_size. The page mapping should also be checked that it is not
-NULL.
+ ->fault() is called when a previously not present pte is about
+to be faulted in. The filesystem must find and return the page associated
+with the passed in "pgoff" in the vm_fault structure. If it is possible that
+the page may be truncated and/or invalidated, then the filesystem must lock
+the page, then ensure it is not already truncated (the page lock will block
+subsequent truncate), and then return with VM_FAULT_LOCKED, and the page
+locked. The VM will unlock the page.
+
+ ->page_mkwrite() is called when a previously read-only pte is
+about to become writeable. The filesystem again must ensure that there are
+no truncate/invalidate races, and then return with the page locked. If
+the page has been truncated, the filesystem should not look up a new page
+like the ->fault() handler, but simply return with VM_FAULT_NOPAGE, which
+will cause the VM to retry the fault.
->access() is called when get_user_pages() fails in
acces_process_vm(), typically used to debug a process through
diff --git a/Documentation/filesystems/caching/cachefiles.txt b/Documentation/filesystems/caching/cachefiles.txt
index c78a49b7bba..748a1ae49e1 100644
--- a/Documentation/filesystems/caching/cachefiles.txt
+++ b/Documentation/filesystems/caching/cachefiles.txt
@@ -407,7 +407,7 @@ A NOTE ON SECURITY
==================
CacheFiles makes use of the split security in the task_struct. It allocates
-its own task_security structure, and redirects current->act_as to point to it
+its own task_security structure, and redirects current->cred to point to it
when it acts on behalf of another process, in that process's context.
The reason it does this is that it calls vfs_mkdir() and suchlike rather than
@@ -429,9 +429,9 @@ This means it may lose signals or ptrace events for example, and affects what
the process looks like in /proc.
So CacheFiles makes use of a logical split in the security between the
-objective security (task->sec) and the subjective security (task->act_as). The
-objective security holds the intrinsic security properties of a process and is
-never overridden. This is what appears in /proc, and is what is used when a
+objective security (task->real_cred) and the subjective security (task->cred).
+The objective security holds the intrinsic security properties of a process and
+is never overridden. This is what appears in /proc, and is what is used when a
process is the target of an operation by some other process (SIGKILL for
example).
diff --git a/Documentation/filesystems/tmpfs.txt b/Documentation/filesystems/tmpfs.txt
index 222437efd75..3015da0c6b2 100644
--- a/Documentation/filesystems/tmpfs.txt
+++ b/Documentation/filesystems/tmpfs.txt
@@ -133,4 +133,4 @@ RAM/SWAP in 10240 inodes and it is only accessible by root.
Author:
Christoph Rohland <cr@sap.com>, 1.12.01
Updated:
- Hugh Dickins <hugh@veritas.com>, 4 June 2007
+ Hugh Dickins, 4 June 2007