What is gfp kernel

Definition at line 33 of file gfp. Definition at line 22 of file gfp. Definition at line 35 of file gfp. Definition at line 32 of file gfp. Definition at line 23 of file gfp. Definition at line 31 of file gfp. Definition at line 17 of file gfp. Definition at line 36 of file gfp.

Definition at line 28 of file gfp. Definition at line of file gfp. Definition at line 96 of file gfp. Definition at line 95 of file gfp. Definition at line 71 of file gfp.

Definition at line 77 of file gfp. Definition at line 47 of file gfp. Definition at line 49 of file gfp. Definition at line 70 of file gfp. Definition at line 80 of file gfp. Definition at line 68 of file gfp. Add a comment. Active Oldest Votes. Improve this answer. Ilya Matveychikov Ilya Matveychikov 3, 1 1 gold badge 23 23 silver badges 41 41 bronze badges. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password.

Post as a guest Name. Email Required, but never shown. The Overflow Blog. Does ES6 make JavaScript frameworks obsolete? Add an arbitrary waiter to the wait queue for the nominated page. However, this will not atomically search a snapshot of the cache at a single point in time. In the rare case of index wrap-around, 0 will be returned.

If there is a page cache page, it is returned with an increased refcount. If there is a page cache page, it is returned locked and with an increased refcount. We update index to index the next page for the traversal. The goto's are kind of ugly, but this streamlines the normal case of having it in the page cache, and handles the special cases reasonably without having a lot of duplicated code. Read into the page cache. If a page already exists, and PageUptodate is not set, try to fill the page and wait for it to become unlocked.

This function does all the work needed for actually writing data to a file. It does all basic checks, removes SUID from the file, updates modification times and calls proper subroutines depending on whether we do direct IO or a standard buffered write.

A caller has to handle it. Processes which are dirtying memory should call in here once for each page which was newly dirtied. The function will periodically check the system's dirty state and will initiate writeback if needed. This mechanism is used to avoid livelocking of writeback by a process steadily creating new dirty pages in the file thus it is important for this function to be quick so that it can tag pages faster than a dirtying process can create them.

To avoid livelocks when other process dirties new pages , we first tag pages which should be written back with TOWRITE tag and only then start writing them. For data-integrity sync we have to be careful so that we do not miss some pages e. This function determines if the given page is related to a backing device that requires page contents to be held stable during writeback.

If so, then it will wait for any pending writeback to complete. Truncate takes two passes - the first pass is nonblocking. It will not block on page locks and it will not block on writeback. The second pass will wait. This is to prevent as much IO as possible in the affected region. The first pass will remove most pages, so the search cost of the second pass is low.

We pass down the cache-hot hint to the page freeing code. Even if the mapping is large, it is probably the case that the final pages are the most recently touched, and freeing happens in ascending file offset order. Filesystems have to use this in the. It will not invalidate pages which are dirty, locked, under writeback or mapped into pagetables.

This function should typically be called before the filesystem releases resources associated with the freed range eg. This way, pagecache will always stay logically coherent with on-disk format, and the filesystem would not have to deal with situations such as writepage being called for a page that has already had its underlying blocks deallocated.

Free all reserved elements in pool and pool itself. May be called on a zeroed but uninitialized mempool i. This function might sleep. This function may sleep. Note that due to preallocation, this function never fails when called from process contexts. Such memory will all have "consistent" DMA mappings, accessible by the device and its driver without using cache flushing primitives.

The actual size of blocks allocated may be larger than requested because of alignment. This is useful for devices which have addressing restrictions on individual DMA transfers, such as not crossing boundaries of 4KBytes. Caller guarantees that no more memory from the pool is in use, and that nothing will try to use the pool after this call. If such a memory block can't be allocated, NULL is returned. Caller promises neither device nor driver will again touch this block unless it is first re-allocated.

DMA pool created with this function is automatically destroyed on driver detach. This doesn't allow that. Your vma protection will have to be set up correctly, which means that if you want a shared writable mapping, you'd better ask for a shared writable mapping! If we fail to insert any page into the vma, the function will return immediately leaving any previously inserted pages present.

Callers from the mmap handler may immediately return the error as their caller will destroy the vma, removing any successfully inserted pages. Process context. Same comments apply. As this is called only for pages that do not currently exist, we do not need to flush old virtual caches or the TLB. See for example mprotect. The driver just needs to give us the physical memory range to be mapped, we'll figure out the rest from the vma information.

For each zone, the number of pages is calculated as:. We use a number of factors to determine which is the next node that should appear on a given node's fallback list. The node should not have appeared already in node 's fallback list, and it should be the next closest node according to the distance array which contains arbitrary distance values from each node to each node in the system , and should also prefer nodes with no CPUs, since presumably they'll have very little allocation pressure on them otherwise.

If called for a node with no available memory, a warning is printed and the start and end PFNs will be 0. This function should be called after node map is populated and sorted.

It calculates the maximum power of two alignment which can distinguish all the nodes. If the nodes are shifted by MiB, MiB. Note that if only the last node is shifted, 1GiB is enough and this function will indicate so. If the maximum PFN between two adjacent zones match, it is assumed that the zone is empty. It is also assumed that a zone starts where the previous one ended. In the DMA zone, a significant percentage may be consumed by kernel image and other unfreeable allocations which can skew the watermarks badly.

This function may optionally be used to account for unfreeable pages in the first zone e. The effect will be lower watermarks and smaller per-cpu batchsize. The PFN range must belong to a single zone. Once isolated, the pageblocks should not be modified by others. This routine is intended for allocation requests which can not be fulfilled with the buddy allocator. The allocated memory is always aligned to a page boundary.

The Linux Kernel 5. This function may sleep if pagefaults are enabled. Description Checks if a pointer to a block of memory in user space is valid. Return true nonzero if the memory block may be valid, false zero if it is definitely invalid.

Parameters x Variable to store result. Context User context only. Description This macro copies a single simple variable from user space to kernel space.