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2007-07-26memory unplug: migration by kernelKAMEZAWA Hiroyuki
In usual, migrate_pages(page,,) is called with holding mm->sem by system call. (mm here is a mm_struct which maps the migration target page.) This semaphore helps avoiding some race conditions. But, if we want to migrate a page by some kernel codes, we have to avoid some races. This patch adds check code for following race condition. 1. A page which page->mapping==NULL can be target of migration. Then, we have to check page->mapping before calling try_to_unmap(). 2. anon_vma can be freed while page is unmapped, but page->mapping remains as it was. We drop page->mapcount to be 0. Then we cannot trust page->mapping. So, use rcu_read_lock() to prevent anon_vma pointed by page->mapping from being freed during migration. Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Acked-by: Christoph Lameter <clameter@sgi.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-07-17Add __GFP_MOVABLE for callers to flag allocations from high memory that may ↵Mel Gorman
be migrated It is often known at allocation time whether a page may be migrated or not. This patch adds a flag called __GFP_MOVABLE and a new mask called GFP_HIGH_MOVABLE. Allocations using the __GFP_MOVABLE can be either migrated using the page migration mechanism or reclaimed by syncing with backing storage and discarding. An API function very similar to alloc_zeroed_user_highpage() is added for __GFP_MOVABLE allocations called alloc_zeroed_user_highpage_movable(). The flags used by alloc_zeroed_user_highpage() are not changed because it would change the semantics of an existing API. After this patch is applied there are no in-kernel users of alloc_zeroed_user_highpage() so it probably should be marked deprecated if this patch is merged. Note that this patch includes a minor cleanup to the use of __GFP_ZERO in shmem.c to keep all flag modifications to inode->mapping in the shmem_dir_alloc() helper function. This clean-up suggestion is courtesy of Hugh Dickens. Additional credit goes to Christoph Lameter and Linus Torvalds for shaping the concept. Credit to Hugh Dickens for catching issues with shmem swap vector and ramfs allocations. [akpm@linux-foundation.org: build fix] [hugh@veritas.com: __GFP_ZERO cleanup] Signed-off-by: Mel Gorman <mel@csn.ul.ie> Cc: Andy Whitcroft <apw@shadowen.org> Cc: Christoph Lameter <clameter@sgi.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-04-24page migration: fix NR_FILE_PAGES accountingChristoph Lameter
NR_FILE_PAGES must be accounted for depending on the zone that the page belongs to. If we replace the page in the radix tree then we may have to shift the count to another zone. Suggested-by: Ethan Solomita <solo@google.com> Eventually-typed-in-by: Christoph Lameter <clameter@sgi.com> Cc: Martin Bligh <mbligh@mbligh.org> Cc: <stable@kernel.org> Signed-off-by: Christoph Lameter <clameter@sgi.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-03-05[PATCH] Page migration: Fix vma flag checkingChristoph Lameter
Currently we do not check for vma flags if sys_move_pages is called to move individual pages. If sys_migrate_pages is called to move pages then we check for vm_flags that indicate a non migratable vma but that still includes VM_LOCKED and we can migrate mlocked pages. Extract the vma_migratable check from mm/mempolicy.c, fix it and put it into migrate.h so that is can be used from both locations. Problem was spotted by Lee Schermerhorn Signed-off-by: Christoph Lameter <clameter@sgi.com> Signed-off-by: Lee Schermerhorn <lee.schermerhorn@hp.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2006-12-07[PATCH] radix-tree: RCU lockless readsideNick Piggin
Make radix tree lookups safe to be performed without locks. Readers are protected against nodes being deleted by using RCU based freeing. Readers are protected against new node insertion by using memory barriers to ensure the node itself will be properly written before it is visible in the radix tree. Each radix tree node keeps a record of their height (above leaf nodes). This height does not change after insertion -- when the radix tree is extended, higher nodes are only inserted in the top. So a lookup can take the pointer to what is *now* the root node, and traverse down it even if the tree is concurrently extended and this node becomes a subtree of a new root. "Direct" pointers (tree height of 0, where root->rnode points directly to the data item) are handled by using the low bit of the pointer to signal whether rnode is a direct pointer or a pointer to a radix tree node. When a reader wants to traverse the next branch, they will take a copy of the pointer. This pointer will be either NULL (and the branch is empty) or non-NULL (and will point to a valid node). [akpm@osdl.org: cleanups] [Lee.Schermerhorn@hp.com: bugfixes, comments, simplifications] [clameter@sgi.com: build fix] Signed-off-by: Nick Piggin <npiggin@suse.de> Cc: "Paul E. McKenney" <paulmck@us.ibm.com> Signed-off-by: Lee Schermerhorn <lee.schermerhorn@hp.com> Cc: Christoph Lameter <clameter@engr.sgi.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-11-03[PATCH] Fix sys_move_pages when a NULL node list is passedStephen Rothwell
sys_move_pages() uses vmalloc() to allocate an array of structures that is fills with information passed from user mode and then passes to do_stat_pages() (in the case the node list is NULL). do_stat_pages() depends on a marker in the node field of the structure to decide how large the array is and this marker is correctly inserted into the last element of the array. However, vmalloc() doesn't zero the memory it allocates and if the user passes NULL for the node list, then the node fields are not filled in (except for the end marker). If the memory the vmalloc() returned happend to have a word with the marker value in it in just the right place, do_pages_stat will fail to fill the status field of part of the array and we will return (random) kernel data to user mode. Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Christoph Lameter <clameter@engr.sgi.com> Cc: <stable@kernel.org> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-09-30[PATCH] BLOCK: Make it possible to disable the block layer [try #6]David Howells
Make it possible to disable the block layer. Not all embedded devices require it, some can make do with just JFFS2, NFS, ramfs, etc - none of which require the block layer to be present. This patch does the following: (*) Introduces CONFIG_BLOCK to disable the block layer, buffering and blockdev support. (*) Adds dependencies on CONFIG_BLOCK to any configuration item that controls an item that uses the block layer. This includes: (*) Block I/O tracing. (*) Disk partition code. (*) All filesystems that are block based, eg: Ext3, ReiserFS, ISOFS. (*) The SCSI layer. As far as I can tell, even SCSI chardevs use the block layer to do scheduling. Some drivers that use SCSI facilities - such as USB storage - end up disabled indirectly from this. (*) Various block-based device drivers, such as IDE and the old CDROM drivers. (*) MTD blockdev handling and FTL. (*) JFFS - which uses set_bdev_super(), something it could avoid doing by taking a leaf out of JFFS2's book. (*) Makes most of the contents of linux/blkdev.h, linux/buffer_head.h and linux/elevator.h contingent on CONFIG_BLOCK being set. sector_div() is, however, still used in places, and so is still available. (*) Also made contingent are the contents of linux/mpage.h, linux/genhd.h and parts of linux/fs.h. (*) Makes a number of files in fs/ contingent on CONFIG_BLOCK. (*) Makes mm/bounce.c (bounce buffering) contingent on CONFIG_BLOCK. (*) set_page_dirty() doesn't call __set_page_dirty_buffers() if CONFIG_BLOCK is not enabled. (*) fs/no-block.c is created to hold out-of-line stubs and things that are required when CONFIG_BLOCK is not set: (*) Default blockdev file operations (to give error ENODEV on opening). (*) Makes some /proc changes: (*) /proc/devices does not list any blockdevs. (*) /proc/diskstats and /proc/partitions are contingent on CONFIG_BLOCK. (*) Makes some compat ioctl handling contingent on CONFIG_BLOCK. (*) If CONFIG_BLOCK is not defined, makes sys_quotactl() return -ENODEV if given command other than Q_SYNC or if a special device is specified. (*) In init/do_mounts.c, no reference is made to the blockdev routines if CONFIG_BLOCK is not defined. This does not prohibit NFS roots or JFFS2. (*) The bdflush, ioprio_set and ioprio_get syscalls can now be absent (return error ENOSYS by way of cond_syscall if so). (*) The seclvl_bd_claim() and seclvl_bd_release() security calls do nothing if CONFIG_BLOCK is not set, since they can't then happen. Signed-Off-By: David Howells <dhowells@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2006-09-30[PATCH] BLOCK: Stop fallback_migrate_page() from using page_has_buffers() ↵David Howells
[try #6] Stop fallback_migrate_page() from using page_has_buffers() since that might not be available. Use PagePrivate() instead since that's more general. Signed-Off-By: David Howells <dhowells@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2006-09-26[PATCH] Define easier to handle GFP_THISNODEChristoph Lameter
In many places we will need to use the same combination of flags. Specify a single GFP_THISNODE definition for ease of use in gfp.h. Signed-off-by: Christoph Lameter <clameter@sgi.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-09-26[PATCH] sys_move_pages: Do not fall back to other nodesChristoph Lameter
If the user specified a node where we should move the page to then we really do not want any other node. Signed-off-by: Christoph Lameter <clameter@sgi.com> Cc: Andy Whitcroft <apw@shadowen.org> Cc: Mel Gorman <mel@csn.ul.ie> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-25[PATCH] Allow migration of mlocked pagesChristoph Lameter
Hugh clarified the role of VM_LOCKED. So we can now implement page migration for mlocked pages. Allow the migration of mlocked pages. This means that try_to_unmap must unmap mlocked pages in the migration case. Signed-off-by: Christoph Lameter <clameter@sgi.com> Acked-by: Hugh Dickins <hugh@veritas.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-25[PATCH] page migration: Support a vma migration functionChristoph Lameter
Hooks for calling vma specific migration functions With this patch a vma may define a vma->vm_ops->migrate function. That function may perform page migration on its own (some vmas may not contain page structs and therefore cannot be handled by regular page migration. Pages in a vma may require special preparatory treatment before migration is possible etc) . Only mmap_sem is held when the migration function is called. The migrate() function gets passed two sets of nodemasks describing the source and the target of the migration. The flags parameter either contains MPOL_MF_MOVE which means that only pages used exclusively by the specified mm should be moved or MPOL_MF_MOVE_ALL which means that pages shared with other processes should also be moved. The migration function returns 0 on success or an error condition. An error condition will prevent regular page migration from occurring. On its own this patch cannot be included since there are no users for this functionality. But it seems that the uncached allocator will need this functionality at some point. Signed-off-by: Christoph Lameter <clameter@sgi.com> Cc: Hugh Dickins <hugh@veritas.com> Cc: Andi Kleen <ak@muc.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-23[PATCH] SELinux: add security_task_movememory calls to mm codeDavid Quigley
This patch inserts security_task_movememory hook calls into memory management code to enable security modules to mediate this operation between tasks. Since the last posting, the hook has been renamed following feedback from Christoph Lameter. Signed-off-by: David Quigley <dpquigl@tycho.nsa.gov> Acked-by: Stephen Smalley <sds@tycho.nsa.gov> Signed-off-by: James Morris <jmorris@namei.org> Cc: Andi Kleen <ak@muc.de> Acked-by: Christoph Lameter <clameter@sgi.com> Acked-by: Chris Wright <chrisw@sous-sol.org> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-23[PATCH] page migration: sys_move_pages(): support moving of individual pagesChristoph Lameter
move_pages() is used to move individual pages of a process. The function can be used to determine the location of pages and to move them onto the desired node. move_pages() returns status information for each page. long move_pages(pid, number_of_pages_to_move, addresses_of_pages[], nodes[] or NULL, status[], flags); The addresses of pages is an array of void * pointing to the pages to be moved. The nodes array contains the node numbers that the pages should be moved to. If a NULL is passed instead of an array then no pages are moved but the status array is updated. The status request may be used to determine the page state before issuing another move_pages() to move pages. The status array will contain the state of all individual page migration attempts when the function terminates. The status array is only valid if move_pages() completed successfullly. Possible page states in status[]: 0..MAX_NUMNODES The page is now on the indicated node. -ENOENT Page is not present -EACCES Page is mapped by multiple processes and can only be moved if MPOL_MF_MOVE_ALL is specified. -EPERM The page has been mlocked by a process/driver and cannot be moved. -EBUSY Page is busy and cannot be moved. Try again later. -EFAULT Invalid address (no VMA or zero page). -ENOMEM Unable to allocate memory on target node. -EIO Unable to write back page. The page must be written back in order to move it since the page is dirty and the filesystem does not provide a migration function that would allow the moving of dirty pages. -EINVAL A dirty page cannot be moved. The filesystem does not provide a migration function and has no ability to write back pages. The flags parameter indicates what types of pages to move: MPOL_MF_MOVE Move pages that are only mapped by the process. MPOL_MF_MOVE_ALL Also move pages that are mapped by multiple processes. Requires sufficient capabilities. Possible return codes from move_pages() -ENOENT No pages found that would require moving. All pages are either already on the target node, not present, had an invalid address or could not be moved because they were mapped by multiple processes. -EINVAL Flags other than MPOL_MF_MOVE(_ALL) specified or an attempt to migrate pages in a kernel thread. -EPERM MPOL_MF_MOVE_ALL specified without sufficient priviledges. or an attempt to move a process belonging to another user. -EACCES One of the target nodes is not allowed by the current cpuset. -ENODEV One of the target nodes is not online. -ESRCH Process does not exist. -E2BIG Too many pages to move. -ENOMEM Not enough memory to allocate control array. -EFAULT Parameters could not be accessed. A test program for move_pages() may be found with the patches on ftp.kernel.org:/pub/linux/kernel/people/christoph/pmig/patches-2.6.17-rc4-mm3 From: Christoph Lameter <clameter@sgi.com> Detailed results for sys_move_pages() Pass a pointer to an integer to get_new_page() that may be used to indicate where the completion status of a migration operation should be placed. This allows sys_move_pags() to report back exactly what happened to each page. Wish there would be a better way to do this. Looks a bit hacky. Signed-off-by: Christoph Lameter <clameter@sgi.com> Cc: Hugh Dickins <hugh@veritas.com> Cc: Jes Sorensen <jes@trained-monkey.org> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Lee Schermerhorn <lee.schermerhorn@hp.com> Cc: Andi Kleen <ak@muc.de> Cc: Michael Kerrisk <mtk-manpages@gmx.net> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-23[PATCH] page migration: use allocator function for migrate_pages()Christoph Lameter
Instead of passing a list of new pages, pass a function to allocate a new page. This allows the correct placement of MPOL_INTERLEAVE pages during page migration. It also further simplifies the callers of migrate pages. migrate_pages() becomes similar to migrate_pages_to() so drop migrate_pages_to(). The batching of new page allocations becomes unnecessary. Signed-off-by: Christoph Lameter <clameter@sgi.com> Cc: Hugh Dickins <hugh@veritas.com> Cc: Jes Sorensen <jes@trained-monkey.org> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Lee Schermerhorn <lee.schermerhorn@hp.com> Cc: Andi Kleen <ak@muc.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-23[PATCH] page migration: handle freeing of pages in migrate_pages()Christoph Lameter
Do not leave pages on the lists passed to migrate_pages(). Seems that we will not need any postprocessing of pages. This will simplify the handling of pages by the callers of migrate_pages(). Signed-off-by: Christoph Lameter <clameter@sgi.com> Cc: Hugh Dickins <hugh@veritas.com> Cc: Jes Sorensen <jes@trained-monkey.org> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Lee Schermerhorn <lee.schermerhorn@hp.com> Cc: Andi Kleen <ak@muc.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-23[PATCH] page migration: simplify migrate_pages()Christoph Lameter
Currently migrate_pages() is mess with lots of goto. Extract two functions from migrate_pages() and get rid of the gotos. Plus we can just unconditionally set the locked bit on the new page since we are the only one holding a reference. Locking is to stop others from accessing the page once we establish references to the new page. Remove the list_del from move_to_lru in order to have finer control over list processing. [akpm@osdl.org: add debug check] Signed-off-by: Christoph Lameter <clameter@sgi.com> Cc: Hugh Dickins <hugh@veritas.com> Cc: Jes Sorensen <jes@trained-monkey.org> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Lee Schermerhorn <lee.schermerhorn@hp.com> Cc: Andi Kleen <ak@muc.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-23[PATCH] More page migration: use migration entries for file pagesChristoph Lameter
This implements the use of migration entries to preserve ptes of file backed pages during migration. Processes can therefore be migrated back and forth without loosing their connection to pagecache pages. Note that we implement the migration entries only for linear mappings. Nonlinear mappings still require the unmapping of the ptes for migration. And another writepage() ugliness shows up. writepage() can drop the page lock. Therefore we have to remove migration ptes before calling writepages() in order to avoid having migration entries point to unlocked pages. Signed-off-by: Christoph Lameter <clameter@sgi.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-23[PATCH] More page migration: do not inc/dec rss countersChristoph Lameter
If we install a migration entry then the rss not really decreases since the page is just moved somewhere else. We can save ourselves the work of decrementing and later incrementing which will just eventually cause cacheline bouncing. Signed-off-by: Christoph Lameter <clameter@sgi.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-23[PATCH] Swapless page migration: modify core logicChristoph Lameter
Use the migration entries for page migration This modifies the migration code to use the new migration entries. It now becomes possible to migrate anonymous pages without having to add a swap entry. We add a couple of new functions to replace migration entries with the proper ptes. We cannot take the tree_lock for migrating anonymous pages anymore. However, we know that we hold the only remaining reference to the page when the page count reaches 1. Signed-off-by: Christoph Lameter <clameter@sgi.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-23[PATCH] Swapless page migration: rip out swap based logicChristoph Lameter
Rip the page migration logic out. Remove all code that has to do with swapping during page migration. This also guts the ability to migrate pages to swap. No one used that so lets let it go for good. Page migration should be a bit broken after this patch. Signed-off-by: Christoph Lameter <clameter@sgi.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-23[PATCH] Swapless page migration: add R/W migration entriesChristoph Lameter
Implement read/write migration ptes We take the upper two swapfiles for the two types of migration ptes and define a series of macros in swapops.h. The VM is modified to handle the migration entries. migration entries can only be encountered when the page they are pointing to is locked. This limits the number of places one has to fix. We also check in copy_pte_range and in mprotect_pte_range() for migration ptes. We check for migration ptes in do_swap_cache and call a function that will then wait on the page lock. This allows us to effectively stop all accesses to apge. Migration entries are created by try_to_unmap if called for migration and removed by local functions in migrate.c From: Hugh Dickins <hugh@veritas.com> Several times while testing swapless page migration (I've no NUMA, just hacking it up to migrate recklessly while running load), I've hit the BUG_ON(!PageLocked(p)) in migration_entry_to_page. This comes from an orphaned migration entry, unrelated to the current correctly locked migration, but hit by remove_anon_migration_ptes as it checks an address in each vma of the anon_vma list. Such an orphan may be left behind if an earlier migration raced with fork: copy_one_pte can duplicate a migration entry from parent to child, after remove_anon_migration_ptes has checked the child vma, but before it has removed it from the parent vma. (If the process were later to fault on this orphaned entry, it would hit the same BUG from migration_entry_wait.) This could be fixed by locking anon_vma in copy_one_pte, but we'd rather not. There's no such problem with file pages, because vma_prio_tree_add adds child vma after parent vma, and the page table locking at each end is enough to serialize. Follow that example with anon_vma: add new vmas to the tail instead of the head. (There's no corresponding problem when inserting migration entries, because a missed pte will leave the page count and mapcount high, which is allowed for. And there's no corresponding problem when migrating via swap, because a leftover swap entry will be correctly faulted. But the swapless method has no refcounting of its entries.) From: Ingo Molnar <mingo@elte.hu> pte_unmap_unlock() takes the pte pointer as an argument. From: Hugh Dickins <hugh@veritas.com> Several times while testing swapless page migration, gcc has tried to exec a pointer instead of a string: smells like COW mappings are not being properly write-protected on fork. The protection in copy_one_pte looks very convincing, until at last you realize that the second arg to make_migration_entry is a boolean "write", and SWP_MIGRATION_READ is 30. Anyway, it's better done like in change_pte_range, using is_write_migration_entry and make_migration_entry_read. From: Hugh Dickins <hugh@veritas.com> Remove unnecessary obfuscation from sys_swapon's range check on swap type, which blew up causing memory corruption once swapless migration made MAX_SWAPFILES no longer 2 ^ MAX_SWAPFILES_SHIFT. Signed-off-by: Hugh Dickins <hugh@veritas.com> Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com> Signed-off-by: Hugh Dickins <hugh@veritas.com> Signed-off-by: Christoph Lameter <clameter@engr.sgi.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> From: Hugh Dickins <hugh@veritas.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-23[PATCH] page migration cleanup: move fallback handling into special functionChristoph Lameter
Move the fallback code into a new fallback function and make the function behave like any other migration function. This requires retaking the lock if pageout() drops it. Signed-off-by: Christoph Lameter <clameter@sgi.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-23[PATCH] page migration cleanup: pass "mapping" to migration functionsChristoph Lameter
Change handling of address spaces. Pass a pointer to the address space in which the page is migrated to all migration function. This avoids repeatedly having to retrieve the address space pointer from the page and checking it for validity. The old page mapping will change once migration has gone to a certain step, so it is less confusing to have the pointer always available. Move the setting of the mapping and index for the new page into migrate_pages(). Signed-off-by: Christoph Lameter <clameter@sgi.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-23[PATCH] page migration cleanup: extract try_to_unmap from migration functionsChristoph Lameter
Extract try_to_unmap and rename remove_references -> move_mapping try_to_unmap() may significantly change the page state by for example setting the dirty bit. It is therefore best to unmap in migrate_pages() before calling any migration functions. migrate_page_remove_references() will then only move the new page in place of the old page in the mapping. Rename the function to migrate_page_move_mapping(). This allows us to get rid of the special unmapping for the fallback path. Signed-off-by: Christoph Lameter <clameter@sgi.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-23[PATCH] page migration cleanup: drop nr_refs in remove_references()Christoph Lameter
Drop nr_refs parameter from migrate_page_remove_references() The nr_refs parameter is not really useful since the number of remaining references is always 1 for anonymous pages without a mapping 2 for pages with a mapping 3 for pages with a mapping and PagePrivate set. Remove the early check for the number of references since we are checking page_mapcount() earlier. Ultimately only the refcount matters after the tree_lock has been obtained. Signed-off-by: Christoph Lameter <clameter@sgi.coim> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-23[PATCH] page migration cleanup: remove useless definitionsChristoph Lameter
Remove the export for migrate_page_remove_references() and migrate_page_copy() that are unlikely to be used directly by filesystems implementing migration. The export was useful when buffer_migrate_page() lived in fs/buffer.c but it has now been moved to migrate.c in the migration reorg. Signed-off-by: Christoph Lameter <clameter@sgi.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-23[PATCH] page migration cleanup: group functionsChristoph Lameter
Reorder functions in migrate.c. Group all migration functions for struct address_space_operations together. Signed-off-by: Christoph Lameter <clameter@sgi.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-05-01[PATCH] page migration: Fix fallback behavior for dirty pagesChristoph Lameter
Currently we check PageDirty() in order to make the decision to swap out the page. However, the dirty information may be only be contained in the ptes pointing to the page. We need to first unmap the ptes before checking for PageDirty(). If unmap is successful then the page count of the page will also be decreased so that pageout() works properly. This is a fix necessary for 2.6.17. Without this fix we may migrate dirty pages for filesystems without migration functions. Filesystems may keep pointers to dirty pages. Migration of dirty pages can result in the filesystem keeping pointers to freed pages. Unmapping is currently not be separated out from removing all the references to a page and moving the mapping. Therefore try_to_unmap will be called again in migrate_page() if the writeout is successful. However, it wont do anything since the ptes are already removed. The coming updates to the page migration code will restructure the code so that this is no longer necessary. Signed-off-by: Christoph Lameter <clameter@sgi.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-04-11[PATCH] mm/migrate.c: don't export a static functionAdrian Bunk
EXPORT_SYMBOL'ing of a static function is not a good idea. Signed-off-by: Adrian Bunk <bunk@stusta.de> Cc: Christoph Lameter <clameter@engr.sgi.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-04-11[PATCH] Some page migration fixupsChristoph Lameter
- Remove sparse comment - Remove duplicated include - Return the correct error condition in migrate_page_remove_references(). Signed-off-by: Christoph Lameter <clameter@sgi.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-03-22[PATCH] page migration reorgChristoph Lameter
Centralize the page migration functions in anticipation of additional tinkering. Creates a new file mm/migrate.c 1. Extract buffer_migrate_page() from fs/buffer.c 2. Extract central migration code from vmscan.c 3. Extract some components from mempolicy.c 4. Export pageout() and remove_from_swap() from vmscan.c 5. Make it possible to configure NUMA systems without page migration and non-NUMA systems with page migration. I had to so some #ifdeffing in mempolicy.c that may need a cleanup. Signed-off-by: Christoph Lameter <clameter@sgi.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>