/* mm/ashmem.c * * Anonymous Shared Memory Subsystem, ashmem * * Copyright (C) 2008 Google, Inc. * * Robert Love <rlove@google.com> * * This software is licensed under the terms of the GNU General Public * License version 2, as published by the Free Software Foundation, and * may be copied, distributed, and modified under those terms. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. */ #define pr_fmt(fmt) "ashmem: " fmt #include <linux/module.h>#include <linux/file.h>#include <linux/fs.h>#include <linux/falloc.h>#include <linux/miscdevice.h>#include <linux/security.h>#include <linux/mm.h>#include <linux/mman.h>#include <linux/uaccess.h>#include <linux/personality.h>#include <linux/bitops.h>#include <linux/mutex.h>#include <linux/shmem_fs.h>#include "ashmem.h" #define ASHMEM_NAME_PREFIX "dev/ashmem/"#define ASHMEM_NAME_PREFIX_LEN (sizeof(ASHMEM_NAME_PREFIX) - 1)#define ASHMEM_FULL_NAME_LEN (ASHMEM_NAME_LEN + ASHMEM_NAME_PREFIX_LEN) /** * struct ashmem_area - The anonymous shared memory area * @name: The optional name in /proc/pid/maps * @unpinned_list: The list of all ashmem areas * @file: The shmem-based backing file * @size: The size of the mapping, in bytes * @prot_masks: The allowed protection bits, as vm_flags * * The lifecycle of this structure is from our parent file's open() until * its release(). It is also protected by 'ashmem_mutex' * * Warning: Mappings do NOT pin this structure; It dies on close() */struct ashmem_area { char name[ASHMEM_FULL_NAME_LEN]; struct list_head unpinned_list; struct file *file; size_t size; unsigned long prot_mask;}; /** * struct ashmem_range - A range of unpinned/evictable pages * @lru: The entry in the LRU list * @unpinned: The entry in its area's unpinned list * @asma: The associated anonymous shared memory area. * @pgstart: The starting page (inclusive) * @pgend: The ending page (inclusive) * @purged: The purge status (ASHMEM_NOT or ASHMEM_WAS_PURGED) * * The lifecycle of this structure is from unpin to pin. * It is protected by 'ashmem_mutex' */struct ashmem_range { struct list_head lru; struct list_head unpinned; struct ashmem_area *asma; size_t pgstart; size_t pgend; unsigned int purged;}; /* LRU list of unpinned pages, protected by ashmem_mutex */static LIST_HEAD(ashmem_lru_list); /** * long lru_count - The count of pages on our LRU list. * * This is protected by ashmem_mutex. */static unsigned long lru_count; /** * ashmem_mutex - protects the list of and each individual ashmem_area * * Lock Ordering: ashmex_mutex -> i_mutex -> i_alloc_sem */static DEFINE_MUTEX(ashmem_mutex); static struct kmem_cache *ashmem_area_cachep __read_mostly;static struct kmem_cache *ashmem_range_cachep __read_mostly; #define range_size(range) \ ((range)->pgend - (range)->pgstart + 1) #define range_on_lru(range) \ ((range)->purged == ASHMEM_NOT_PURGED) #define page_range_subsumes_range(range, start, end) \ (((range)->pgstart >= (start)) && ((range)->pgend <= (end))) #define page_range_subsumed_by_range(range, start, end) \ (((range)->pgstart <= (start)) && ((range)->pgend >= (end))) #define page_in_range(range, page) \ (((range)->pgstart <= (page)) && ((range)->pgend >= (page))) #define page_range_in_range(range, start, end) \ (page_in_range(range, start) || page_in_range(range, end) || \ page_range_subsumes_range(range, start, end)) #define range_before_page(range, page) \ ((range)->pgend < (page)) #define PROT_MASK (PROT_EXEC | PROT_READ | PROT_WRITE) /** * lru_add() - Adds a range of memory to the LRU list * @range: The memory range being added. * * The range is first added to the end (tail) of the LRU list. * After this, the size of the range is added to @lru_count */static inline void lru_add(struct ashmem_range *range){ list_add_tail(&range->lru, &ashmem_lru_list); lru_count += range_size(range);} /** * lru_del() - Removes a range of memory from the LRU list * @range: The memory range being removed * * The range is first deleted from the LRU list. * After this, the size of the range is removed from @lru_count */static inline void lru_del(struct ashmem_range *range){ list_del(&range->lru); lru_count -= range_size(range);} /** * range_alloc() - Allocates and initializes a new ashmem_range structure * @asma: The associated ashmem_area * @prev_range: The previous ashmem_range in the sorted asma->unpinned list * @purged: Initial purge status (ASMEM_NOT_PURGED or ASHMEM_WAS_PURGED) * @start: The starting page (inclusive) * @end: The ending page (inclusive) * * This function is protected by ashmem_mutex. * * Return: 0 if successful, or -ENOMEM if there is an error */static int range_alloc(struct ashmem_area *asma, struct ashmem_range *prev_range, unsigned int purged, size_t start, size_t end){ struct ashmem_range *range; range = kmem_cache_zalloc(ashmem_range_cachep, GFP_KERNEL); if (unlikely(!range)) return -ENOMEM; range->asma = asma; range->pgstart = start; range->pgend = end; range->purged = purged; list_add_tail(&range->unpinned, &prev_range->unpinned); if (range_on_lru(range)) lru_add(range); return 0;} /** * range_del() - Deletes and dealloctes an ashmem_range structure * @range: The associated ashmem_range that has previously been allocated */static void range_del(struct ashmem_range *range){ list_del(&range->unpinned); if (range_on_lru(range)) lru_del(range); kmem_cache_free(ashmem_range_cachep, range);} /** * range_shrink() - Shrinks an ashmem_range * @range: The associated ashmem_range being shrunk * @start: The starting byte of the new range * @end: The ending byte of the new range * * This does not modify the data inside the existing range in any way - It * simply shrinks the boundaries of the range. * * Theoretically, with a little tweaking, this could eventually be changed * to range_resize, and expand the lru_count if the new range is larger. */static inline void range_shrink(struct ashmem_range *range, size_t start, size_t end){ size_t pre = range_size(range); range->pgstart = start; range->pgend = end; if (range_on_lru(range)) lru_count -= pre - range_size(range);} /** * ashmem_open() - Opens an Anonymous Shared Memory structure * @inode: The backing file's index node(?) * @file: The backing file * * Please note that the ashmem_area is not returned by this function - It is * instead written to "file->private_data". * * Return: 0 if successful, or another code if unsuccessful. */static int ashmem_open(struct inode *inode, struct file *file){ struct ashmem_area *asma; int ret; ret = generic_file_open(inode, file); if (unlikely(ret)) return ret; asma = kmem_cache_zalloc(ashmem_area_cachep, GFP_KERNEL); if (unlikely(!asma)) return -ENOMEM; INIT_LIST_HEAD(&asma->unpinned_list); memcpy(asma->name, ASHMEM_NAME_PREFIX, ASHMEM_NAME_PREFIX_LEN); asma->prot_mask = PROT_MASK; file->private_data = asma; return 0;} /** * ashmem_release() - Releases an Anonymous Shared Memory structure * @ignored: The backing file's Index Node(?) - It is ignored here. * @file: The backing file * * Return: 0 if successful. If it is anything else, go have a coffee and * try again. */static int ashmem_release(struct inode *ignored, struct file *file){ struct ashmem_area *asma = file->private_data; struct ashmem_range *range, *next; mutex_lock(&ashmem_mutex); list_for_each_entry_safe(range, next, &asma->unpinned_list, unpinned) range_del(range); mutex_unlock(&ashmem_mutex); if (asma->file) fput(asma->file); kmem_cache_free(ashmem_area_cachep, asma); return 0;} /** * ashmem_read() - Reads a set of bytes from an Ashmem-enabled file * @file: The associated backing file. * @buf: The buffer of data being written to * @len: The number of bytes being read * @pos: The position of the first byte to read. * * Return: 0 if successful, or another return code if not. */static ssize_t ashmem_read(struct file *file, char __user *buf, size_t len, loff_t *pos){ struct ashmem_area *asma = file->private_data; int ret = 0; mutex_lock(&ashmem_mutex); /* If size is not set, or set to 0, always return EOF. */ if (asma->size == 0) goto out; if (!asma->file) { ret = -EBADF; goto out; } ret = asma->file->f_op->read(asma->file, buf, len, pos); if (ret < 0) goto out; /** Update backing file pos, since f_ops->read() doesn't */ asma->file->f_pos = *pos; out: mutex_unlock(&ashmem_mutex); return ret;} static loff_t ashmem_llseek(struct file *file, loff_t offset, int origin){ struct ashmem_area *asma = file->private_data; int ret; mutex_lock(&ashmem_mutex); if (asma->size == 0) { ret = -EINVAL; goto out; } if (!asma->file) { ret = -EBADF; goto out; } ret = asma->file->f_op->llseek(asma->file, offset, origin); if (ret < 0) goto out; /** Copy f_pos from backing file, since f_ops->llseek() sets it */ file->f_pos = asma->file->f_pos; out: mutex_unlock(&ashmem_mutex); return ret;} static inline vm_flags_t calc_vm_may_flags(unsigned long prot){ return _calc_vm_trans(prot, PROT_READ, VM_MAYREAD) | _calc_vm_trans(prot, PROT_WRITE, VM_MAYWRITE) | _calc_vm_trans(prot, PROT_EXEC, VM_MAYEXEC);} static int ashmem_mmap(struct file *file, struct vm_area_struct *vma){ struct ashmem_area *asma = file->private_data; int ret = 0; mutex_lock(&ashmem_mutex); /* user needs to SET_SIZE before mapping */ if (unlikely(!asma->size)) { ret = -EINVAL; goto out; } /* requested protection bits must match our allowed protection mask */ if (unlikely((vma->vm_flags & ~calc_vm_prot_bits(asma->prot_mask)) & calc_vm_prot_bits(PROT_MASK))) { ret = -EPERM; goto out; } vma->vm_flags &= ~calc_vm_may_flags(~asma->prot_mask); if (!asma->file) { char *name = ASHMEM_NAME_DEF; struct file *vmfile; if (asma->name[ASHMEM_NAME_PREFIX_LEN] != '\0') name = asma->name; /* ... and allocate the backing shmem file */ vmfile = shmem_file_setup(name, asma->size, vma->vm_flags); if (unlikely(IS_ERR(vmfile))) { ret = PTR_ERR(vmfile); goto out; } asma->file = vmfile; } get_file(asma->file); /* * XXX - Reworked to use shmem_zero_setup() instead of * shmem_set_file while we're in staging. -jstultz */ if (vma->vm_flags & VM_SHARED) { ret = shmem_zero_setup(vma); if (ret) { fput(asma->file); goto out; } } if (vma->vm_file) fput(vma->vm_file); vma->vm_file = asma->file; out: mutex_unlock(&ashmem_mutex); return ret;} /* * ashmem_shrink - our cache shrinker, called from mm/vmscan.c :: shrink_slab * * 'nr_to_scan' is the number of objects to scan for freeing. * * 'gfp_mask' is the mask of the allocation that got us into this mess. * * Return value is the number of objects freed or -1 if we cannot * proceed without risk of deadlock (due to gfp_mask). * * We approximate LRU via least-recently-unpinned, jettisoning unpinned partial * chunks of ashmem regions LRU-wise one-at-a-time until we hit 'nr_to_scan' * pages freed. */static unsigned longashmem_shrink_scan(struct shrinker *shrink, struct shrink_control *sc){ struct ashmem_range *range, *next; unsigned long freed = 0; /* We might recurse into filesystem code, so bail out if necessary */ if (!(sc->gfp_mask & __GFP_FS)) return SHRINK_STOP; mutex_lock(&ashmem_mutex); list_for_each_entry_safe(range, next, &ashmem_lru_list, lru) { loff_t start = range->pgstart * PAGE_SIZE; loff_t end = (range->pgend + 1) * PAGE_SIZE; do_fallocate(range->asma->file, FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE, start, end - start); range->purged = ASHMEM_WAS_PURGED; lru_del(range); freed += range_size(range); if (--sc->nr_to_scan <= 0) break; } mutex_unlock(&ashmem_mutex); return freed;} static unsigned longashmem_shrink_count(struct shrinker *shrink, struct shrink_control *sc){ /* * note that lru_count is count of pages on the lru, not a count of * objects on the list. This means the scan function needs to return the * number of pages freed, not the number of objects scanned. */ return lru_count;} static struct shrinker ashmem_shrinker = { .count_objects = ashmem_shrink_count, .scan_objects = ashmem_shrink_scan, /* * XXX (dchinner): I wish people would comment on why they need on * significant changes to the default value here */ .seeks = DEFAULT_SEEKS * 4,}; static int set_prot_mask(struct ashmem_area *asma, unsigned long prot){ int ret = 0; mutex_lock(&ashmem_mutex); /* the user can only remove, not add, protection bits */ if (unlikely((asma->prot_mask & prot) != prot)) { ret = -EINVAL; goto out; } /* does the application expect PROT_READ to imply PROT_EXEC? */ if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC)) prot |= PROT_EXEC; asma->prot_mask = prot; out: mutex_unlock(&ashmem_mutex); return ret;} static int set_name(struct ashmem_area *asma, void __user *name){Lines 1–500 of 879. Load more
/* mm/ashmem.c * * Anonymous Shared Memory Subsystem, ashmem * * Copyright (C) 2008 Google, Inc. * * Robert Love <rlove@google.com> * * This software is licensed under the terms of the GNU General Public * License version 2, as published by the Free Software Foundation, and * may be copied, distributed, and modified under those terms. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. */ #define pr_fmt(fmt) "ashmem: " fmt #include <linux/module.h> #include <linux/file.h> #include <linux/fs.h> #include <linux/falloc.h> #include <linux/miscdevice.h> #include <linux/security.h> #include <linux/mm.h> #include <linux/mman.h> #include <linux/uaccess.h> #include <linux/personality.h> #include <linux/bitops.h> #include <linux/mutex.h> #include <linux/shmem_fs.h> #include "ashmem.h" #define ASHMEM_NAME_PREFIX "dev/ashmem/" #define ASHMEM_NAME_PREFIX_LEN (sizeof(ASHMEM_NAME_PREFIX) - 1) #define ASHMEM_FULL_NAME_LEN (ASHMEM_NAME_LEN + ASHMEM_NAME_PREFIX_LEN) /** * struct ashmem_area - The anonymous shared memory area * @name: The optional name in /proc/pid/maps * @unpinned_list: The list of all ashmem areas * @file: The shmem-based backing file * @size: The size of the mapping, in bytes * @prot_masks: The allowed protection bits, as vm_flags * * The lifecycle of this structure is from our parent file's open() until * its release(). It is also protected by 'ashmem_mutex' * * Warning: Mappings do NOT pin this structure; It dies on close() */ struct ashmem_area { char name[ASHMEM_FULL_NAME_LEN]; struct list_head unpinned_list; struct file *file; size_t size; unsigned long prot_mask; }; /** * struct ashmem_range - A range of unpinned/evictable pages * @lru: The entry in the LRU list * @unpinned: The entry in its area's unpinned list * @asma: The associated anonymous shared memory area. * @pgstart: The starting page (inclusive) * @pgend: The ending page (inclusive) * @purged: The purge status (ASHMEM_NOT or ASHMEM_WAS_PURGED) * * The lifecycle of this structure is from unpin to pin. * It is protected by 'ashmem_mutex' */ struct ashmem_range { struct list_head lru; struct list_head unpinned; struct ashmem_area *asma; size_t pgstart; size_t pgend; unsigned int purged; }; /* LRU list of unpinned pages, protected by ashmem_mutex */ static LIST_HEAD(ashmem_lru_list); /** * long lru_count - The count of pages on our LRU list. * * This is protected by ashmem_mutex. */ static unsigned long lru_count; /** * ashmem_mutex - protects the list of and each individual ashmem_area * * Lock Ordering: ashmex_mutex -> i_mutex -> i_alloc_sem */ static DEFINE_MUTEX(ashmem_mutex); static struct kmem_cache *ashmem_area_cachep __read_mostly; static struct kmem_cache *ashmem_range_cachep __read_mostly; #define range_size(range) \ ((range)->pgend - (range)->pgstart + 1) #define range_on_lru(range) \ ((range)->purged == ASHMEM_NOT_PURGED) #define page_range_subsumes_range(range, start, end) \ (((range)->pgstart >= (start)) && ((range)->pgend <= (end))) #define page_range_subsumed_by_range(range, start, end) \ (((range)->pgstart <= (start)) && ((range)->pgend >= (end))) #define page_in_range(range, page) \ (((range)->pgstart <= (page)) && ((range)->pgend >= (page))) #define page_range_in_range(range, start, end) \ (page_in_range(range, start) || page_in_range(range, end) || \ page_range_subsumes_range(range, start, end)) #define range_before_page(range, page) \ ((range)->pgend < (page)) #define PROT_MASK (PROT_EXEC | PROT_READ | PROT_WRITE) /** * lru_add() - Adds a range of memory to the LRU list * @range: The memory range being added. * * The range is first added to the end (tail) of the LRU list. * After this, the size of the range is added to @lru_count */ static inline void lru_add(struct ashmem_range *range) { list_add_tail(&range->lru, &ashmem_lru_list); lru_count += range_size(range); } /** * lru_del() - Removes a range of memory from the LRU list * @range: The memory range being removed * * The range is first deleted from the LRU list. * After this, the size of the range is removed from @lru_count */ static inline void lru_del(struct ashmem_range *range) { list_del(&range->lru); lru_count -= range_size(range); } /** * range_alloc() - Allocates and initializes a new ashmem_range structure * @asma: The associated ashmem_area * @prev_range: The previous ashmem_range in the sorted asma->unpinned list * @purged: Initial purge status (ASMEM_NOT_PURGED or ASHMEM_WAS_PURGED) * @start: The starting page (inclusive) * @end: The ending page (inclusive) * * This function is protected by ashmem_mutex. * * Return: 0 if successful, or -ENOMEM if there is an error */ static int range_alloc(struct ashmem_area *asma, struct ashmem_range *prev_range, unsigned int purged, size_t start, size_t end) { struct ashmem_range *range; range = kmem_cache_zalloc(ashmem_range_cachep, GFP_KERNEL); if (unlikely(!range)) return -ENOMEM; range->asma = asma; range->pgstart = start; range->pgend = end; range->purged = purged; list_add_tail(&range->unpinned, &prev_range->unpinned); if (range_on_lru(range)) lru_add(range); return 0; } /** * range_del() - Deletes and dealloctes an ashmem_range structure * @range: The associated ashmem_range that has previously been allocated */ static void range_del(struct ashmem_range *range) { list_del(&range->unpinned); if (range_on_lru(range)) lru_del(range); kmem_cache_free(ashmem_range_cachep, range); } /** * range_shrink() - Shrinks an ashmem_range * @range: The associated ashmem_range being shrunk * @start: The starting byte of the new range * @end: The ending byte of the new range * * This does not modify the data inside the existing range in any way - It * simply shrinks the boundaries of the range. * * Theoretically, with a little tweaking, this could eventually be changed * to range_resize, and expand the lru_count if the new range is larger. */ static inline void range_shrink(struct ashmem_range *range, size_t start, size_t end) { size_t pre = range_size(range); range->pgstart = start; range->pgend = end; if (range_on_lru(range)) lru_count -= pre - range_size(range); } /** * ashmem_open() - Opens an Anonymous Shared Memory structure * @inode: The backing file's index node(?) * @file: The backing file * * Please note that the ashmem_area is not returned by this function - It is * instead written to "file->private_data". * * Return: 0 if successful, or another code if unsuccessful. */ static int ashmem_open(struct inode *inode, struct file *file) { struct ashmem_area *asma; int ret; ret = generic_file_open(inode, file); if (unlikely(ret)) return ret; asma = kmem_cache_zalloc(ashmem_area_cachep, GFP_KERNEL); if (unlikely(!asma)) return -ENOMEM; INIT_LIST_HEAD(&asma->unpinned_list); memcpy(asma->name, ASHMEM_NAME_PREFIX, ASHMEM_NAME_PREFIX_LEN); asma->prot_mask = PROT_MASK; file->private_data = asma; return 0; } /** * ashmem_release() - Releases an Anonymous Shared Memory structure * @ignored: The backing file's Index Node(?) - It is ignored here. * @file: The backing file * * Return: 0 if successful. If it is anything else, go have a coffee and * try again. */ static int ashmem_release(struct inode *ignored, struct file *file) { struct ashmem_area *asma = file->private_data; struct ashmem_range *range, *next; mutex_lock(&ashmem_mutex); list_for_each_entry_safe(range, next, &asma->unpinned_list, unpinned) range_del(range); mutex_unlock(&ashmem_mutex); if (asma->file) fput(asma->file); kmem_cache_free(ashmem_area_cachep, asma); return 0; } /** * ashmem_read() - Reads a set of bytes from an Ashmem-enabled file * @file: The associated backing file. * @buf: The buffer of data being written to * @len: The number of bytes being read * @pos: The position of the first byte to read. * * Return: 0 if successful, or another return code if not. */ static ssize_t ashmem_read(struct file *file, char __user *buf, size_t len, loff_t *pos) { struct ashmem_area *asma = file->private_data; int ret = 0; mutex_lock(&ashmem_mutex); /* If size is not set, or set to 0, always return EOF. */ if (asma->size == 0) goto out; if (!asma->file) { ret = -EBADF; goto out; } ret = asma->file->f_op->read(asma->file, buf, len, pos); if (ret < 0) goto out; /** Update backing file pos, since f_ops->read() doesn't */ asma->file->f_pos = *pos; out: mutex_unlock(&ashmem_mutex); return ret; } static loff_t ashmem_llseek(struct file *file, loff_t offset, int origin) { struct ashmem_area *asma = file->private_data; int ret; mutex_lock(&ashmem_mutex); if (asma->size == 0) { ret = -EINVAL; goto out; } if (!asma->file) { ret = -EBADF; goto out; } ret = asma->file->f_op->llseek(asma->file, offset, origin); if (ret < 0) goto out; /** Copy f_pos from backing file, since f_ops->llseek() sets it */ file->f_pos = asma->file->f_pos; out: mutex_unlock(&ashmem_mutex); return ret; } static inline vm_flags_t calc_vm_may_flags(unsigned long prot) { return _calc_vm_trans(prot, PROT_READ, VM_MAYREAD) | _calc_vm_trans(prot, PROT_WRITE, VM_MAYWRITE) | _calc_vm_trans(prot, PROT_EXEC, VM_MAYEXEC); } static int ashmem_mmap(struct file *file, struct vm_area_struct *vma) { struct ashmem_area *asma = file->private_data; int ret = 0; mutex_lock(&ashmem_mutex); /* user needs to SET_SIZE before mapping */ if (unlikely(!asma->size)) { ret = -EINVAL; goto out; } /* requested protection bits must match our allowed protection mask */ if (unlikely((vma->vm_flags & ~calc_vm_prot_bits(asma->prot_mask)) & calc_vm_prot_bits(PROT_MASK))) { ret = -EPERM; goto out; } vma->vm_flags &= ~calc_vm_may_flags(~asma->prot_mask); if (!asma->file) { char *name = ASHMEM_NAME_DEF; struct file *vmfile; if (asma->name[ASHMEM_NAME_PREFIX_LEN] != '\0') name = asma->name; /* ... and allocate the backing shmem file */ vmfile = shmem_file_setup(name, asma->size, vma->vm_flags); if (unlikely(IS_ERR(vmfile))) { ret = PTR_ERR(vmfile); goto out; } asma->file = vmfile; } get_file(asma->file); /* * XXX - Reworked to use shmem_zero_setup() instead of * shmem_set_file while we're in staging. -jstultz */ if (vma->vm_flags & VM_SHARED) { ret = shmem_zero_setup(vma); if (ret) { fput(asma->file); goto out; } } if (vma->vm_file) fput(vma->vm_file); vma->vm_file = asma->file; out: mutex_unlock(&ashmem_mutex); return ret; } /* * ashmem_shrink - our cache shrinker, called from mm/vmscan.c :: shrink_slab * * 'nr_to_scan' is the number of objects to scan for freeing. * * 'gfp_mask' is the mask of the allocation that got us into this mess. * * Return value is the number of objects freed or -1 if we cannot * proceed without risk of deadlock (due to gfp_mask). * * We approximate LRU via least-recently-unpinned, jettisoning unpinned partial * chunks of ashmem regions LRU-wise one-at-a-time until we hit 'nr_to_scan' * pages freed. */ static unsigned long ashmem_shrink_scan(struct shrinker *shrink, struct shrink_control *sc) { struct ashmem_range *range, *next; unsigned long freed = 0; /* We might recurse into filesystem code, so bail out if necessary */ if (!(sc->gfp_mask & __GFP_FS)) return SHRINK_STOP; mutex_lock(&ashmem_mutex); list_for_each_entry_safe(range, next, &ashmem_lru_list, lru) { loff_t start = range->pgstart * PAGE_SIZE; loff_t end = (range->pgend + 1) * PAGE_SIZE; do_fallocate(range->asma->file, FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE, start, end - start); range->purged = ASHMEM_WAS_PURGED; lru_del(range); freed += range_size(range); if (--sc->nr_to_scan <= 0) break; } mutex_unlock(&ashmem_mutex); return freed; } static unsigned long ashmem_shrink_count(struct shrinker *shrink, struct shrink_control *sc) { /* * note that lru_count is count of pages on the lru, not a count of * objects on the list. This means the scan function needs to return the * number of pages freed, not the number of objects scanned. */ return lru_count; } static struct shrinker ashmem_shrinker = { .count_objects = ashmem_shrink_count, .scan_objects = ashmem_shrink_scan, /* * XXX (dchinner): I wish people would comment on why they need on * significant changes to the default value here */ .seeks = DEFAULT_SEEKS * 4, }; static int set_prot_mask(struct ashmem_area *asma, unsigned long prot) { int ret = 0; mutex_lock(&ashmem_mutex); /* the user can only remove, not add, protection bits */ if (unlikely((asma->prot_mask & prot) != prot)) { ret = -EINVAL; goto out; } /* does the application expect PROT_READ to imply PROT_EXEC? */ if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC)) prot |= PROT_EXEC; asma->prot_mask = prot; out: mutex_unlock(&ashmem_mutex); return ret; } static int set_name(struct ashmem_area *asma, void __user *name) {