diff options
Diffstat (limited to 'Documentation/filesystems')
| -rw-r--r-- | Documentation/filesystems/ext2.txt | 2 | ||||
| -rw-r--r-- | Documentation/filesystems/isofs.txt | 6 | ||||
| -rw-r--r-- | Documentation/filesystems/sysfs.txt | 2 | ||||
| -rw-r--r-- | Documentation/filesystems/tmpfs.txt | 6 | ||||
| -rw-r--r-- | Documentation/filesystems/xip.txt | 67 |
5 files changed, 78 insertions, 5 deletions
diff --git a/Documentation/filesystems/ext2.txt b/Documentation/filesystems/ext2.txt index b5cb911..d16334e 100644 --- a/Documentation/filesystems/ext2.txt +++ b/Documentation/filesystems/ext2.txt @@ -58,6 +58,8 @@ noacl Don't support POSIX ACLs. nobh Do not attach buffer_heads to file pagecache. +xip Use execute in place (no caching) if possible + grpquota,noquota,quota,usrquota Quota options are silently ignored by ext2. diff --git a/Documentation/filesystems/isofs.txt b/Documentation/filesystems/isofs.txt index f64a105..424585f 100644 --- a/Documentation/filesystems/isofs.txt +++ b/Documentation/filesystems/isofs.txt @@ -26,7 +26,11 @@ Mount options unique to the isofs filesystem. mode=xxx Sets the permissions on files to xxx nojoliet Ignore Joliet extensions if they are present. norock Ignore Rock Ridge extensions if they are present. - unhide Show hidden files. + hide Completely strip hidden files from the file system. + showassoc Show files marked with the 'associated' bit + unhide Deprecated; showing hidden files is now default; + If given, it is a synonym for 'showassoc' which will + recreate previous unhide behavior session=x Select number of session on multisession CD sbsector=xxx Session begins from sector xxx diff --git a/Documentation/filesystems/sysfs.txt b/Documentation/filesystems/sysfs.txt index 60f6c2c..dc27659 100644 --- a/Documentation/filesystems/sysfs.txt +++ b/Documentation/filesystems/sysfs.txt @@ -214,7 +214,7 @@ Other notes: A very simple (and naive) implementation of a device attribute is: -static ssize_t show_name(struct device * dev, char * buf) +static ssize_t show_name(struct device *dev, struct device_attribute *attr, char *buf) { return sprintf(buf,"%s\n",dev->name); } diff --git a/Documentation/filesystems/tmpfs.txt b/Documentation/filesystems/tmpfs.txt index 417e309..0d783c5 100644 --- a/Documentation/filesystems/tmpfs.txt +++ b/Documentation/filesystems/tmpfs.txt @@ -71,8 +71,8 @@ can be changed on remount. The size parameter also accepts a suffix % to limit this tmpfs instance to that percentage of your physical RAM: the default, when neither size nor nr_blocks is specified, is size=50% -If both nr_blocks (or size) and nr_inodes are set to 0, neither blocks -nor inodes will be limited in that instance. It is generally unwise to +If nr_blocks=0 (or size=0), blocks will not be limited in that instance; +if nr_inodes=0, inodes will not be limited. It is generally unwise to mount with such options, since it allows any user with write access to use up all the memory on the machine; but enhances the scalability of that instance in a system with many cpus making intensive use of it. @@ -97,4 +97,4 @@ 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>, 01 September 2004 + Hugh Dickins <hugh@veritas.com>, 13 March 2005 diff --git a/Documentation/filesystems/xip.txt b/Documentation/filesystems/xip.txt new file mode 100644 index 0000000..6c0cef1 --- /dev/null +++ b/Documentation/filesystems/xip.txt @@ -0,0 +1,67 @@ +Execute-in-place for file mappings +---------------------------------- + +Motivation +---------- +File mappings are performed by mapping page cache pages to userspace. In +addition, read&write type file operations also transfer data from/to the page +cache. + +For memory backed storage devices that use the block device interface, the page +cache pages are in fact copies of the original storage. Various approaches +exist to work around the need for an extra copy. The ramdisk driver for example +does read the data into the page cache, keeps a reference, and discards the +original data behind later on. + +Execute-in-place solves this issue the other way around: instead of keeping +data in the page cache, the need to have a page cache copy is eliminated +completely. With execute-in-place, read&write type operations are performed +directly from/to the memory backed storage device. For file mappings, the +storage device itself is mapped directly into userspace. + +This implementation was initialy written for shared memory segments between +different virtual machines on s390 hardware to allow multiple machines to +share the same binaries and libraries. + +Implementation +-------------- +Execute-in-place is implemented in three steps: block device operation, +address space operation, and file operations. + +A block device operation named direct_access is used to retrieve a +reference (pointer) to a block on-disk. The reference is supposed to be +cpu-addressable, physical address and remain valid until the release operation +is performed. A struct block_device reference is used to address the device, +and a sector_t argument is used to identify the individual block. As an +alternative, memory technology devices can be used for this. + +The block device operation is optional, these block devices support it as of +today: +- dcssblk: s390 dcss block device driver + +An address space operation named get_xip_page is used to retrieve reference +to a struct page. To address the target page, a reference to an address_space, +and a sector number is provided. A 3rd argument indicates whether the +function should allocate blocks if needed. + +This address space operation is mutually exclusive with readpage&writepage that +do page cache read/write operations. +The following filesystems support it as of today: +- ext2: the second extended filesystem, see Documentation/filesystems/ext2.txt + +A set of file operations that do utilize get_xip_page can be found in +mm/filemap_xip.c . The following file operation implementations are provided: +- aio_read/aio_write +- readv/writev +- sendfile + +The generic file operations do_sync_read/do_sync_write can be used to implement +classic synchronous IO calls. + +Shortcomings +------------ +This implementation is limited to storage devices that are cpu addressable at +all times (no highmem or such). It works well on rom/ram, but enhancements are +needed to make it work with flash in read+write mode. +Putting the Linux kernel and/or its modules on a xip filesystem does not mean +they are not copied. |
