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Linux/mm/fadvise.c

  1 /*
  2  * mm/fadvise.c
  3  *
  4  * Copyright (C) 2002, Linus Torvalds
  5  *
  6  * 11Jan2003    Andrew Morton
  7  *              Initial version.
  8  */
  9 
 10 #include <linux/kernel.h>
 11 #include <linux/file.h>
 12 #include <linux/fs.h>
 13 #include <linux/mm.h>
 14 #include <linux/pagemap.h>
 15 #include <linux/backing-dev.h>
 16 #include <linux/pagevec.h>
 17 #include <linux/fadvise.h>
 18 #include <linux/writeback.h>
 19 #include <linux/syscalls.h>
 20 #include <linux/swap.h>
 21 
 22 #include <asm/unistd.h>
 23 
 24 /*
 25  * POSIX_FADV_WILLNEED could set PG_Referenced, and POSIX_FADV_NOREUSE could
 26  * deactivate the pages and clear PG_Referenced.
 27  */
 28 SYSCALL_DEFINE4(fadvise64_64, int, fd, loff_t, offset, loff_t, len, int, advice)
 29 {
 30         struct fd f = fdget(fd);
 31         struct inode *inode;
 32         struct address_space *mapping;
 33         struct backing_dev_info *bdi;
 34         loff_t endbyte;                 /* inclusive */
 35         pgoff_t start_index;
 36         pgoff_t end_index;
 37         unsigned long nrpages;
 38         int ret = 0;
 39 
 40         if (!f.file)
 41                 return -EBADF;
 42 
 43         inode = file_inode(f.file);
 44         if (S_ISFIFO(inode->i_mode)) {
 45                 ret = -ESPIPE;
 46                 goto out;
 47         }
 48 
 49         mapping = f.file->f_mapping;
 50         if (!mapping || len < 0) {
 51                 ret = -EINVAL;
 52                 goto out;
 53         }
 54 
 55         if (IS_DAX(inode)) {
 56                 switch (advice) {
 57                 case POSIX_FADV_NORMAL:
 58                 case POSIX_FADV_RANDOM:
 59                 case POSIX_FADV_SEQUENTIAL:
 60                 case POSIX_FADV_WILLNEED:
 61                 case POSIX_FADV_NOREUSE:
 62                 case POSIX_FADV_DONTNEED:
 63                         /* no bad return value, but ignore advice */
 64                         break;
 65                 default:
 66                         ret = -EINVAL;
 67                 }
 68                 goto out;
 69         }
 70 
 71         /* Careful about overflows. Len == 0 means "as much as possible" */
 72         endbyte = offset + len;
 73         if (!len || endbyte < len)
 74                 endbyte = -1;
 75         else
 76                 endbyte--;              /* inclusive */
 77 
 78         bdi = inode_to_bdi(mapping->host);
 79 
 80         switch (advice) {
 81         case POSIX_FADV_NORMAL:
 82                 f.file->f_ra.ra_pages = bdi->ra_pages;
 83                 spin_lock(&f.file->f_lock);
 84                 f.file->f_mode &= ~FMODE_RANDOM;
 85                 spin_unlock(&f.file->f_lock);
 86                 break;
 87         case POSIX_FADV_RANDOM:
 88                 spin_lock(&f.file->f_lock);
 89                 f.file->f_mode |= FMODE_RANDOM;
 90                 spin_unlock(&f.file->f_lock);
 91                 break;
 92         case POSIX_FADV_SEQUENTIAL:
 93                 f.file->f_ra.ra_pages = bdi->ra_pages * 2;
 94                 spin_lock(&f.file->f_lock);
 95                 f.file->f_mode &= ~FMODE_RANDOM;
 96                 spin_unlock(&f.file->f_lock);
 97                 break;
 98         case POSIX_FADV_WILLNEED:
 99                 /* First and last PARTIAL page! */
100                 start_index = offset >> PAGE_SHIFT;
101                 end_index = endbyte >> PAGE_SHIFT;
102 
103                 /* Careful about overflow on the "+1" */
104                 nrpages = end_index - start_index + 1;
105                 if (!nrpages)
106                         nrpages = ~0UL;
107 
108                 /*
109                  * Ignore return value because fadvise() shall return
110                  * success even if filesystem can't retrieve a hint,
111                  */
112                 force_page_cache_readahead(mapping, f.file, start_index,
113                                            nrpages);
114                 break;
115         case POSIX_FADV_NOREUSE:
116                 break;
117         case POSIX_FADV_DONTNEED:
118                 if (!inode_write_congested(mapping->host))
119                         __filemap_fdatawrite_range(mapping, offset, endbyte,
120                                                    WB_SYNC_NONE);
121 
122                 /*
123                  * First and last FULL page! Partial pages are deliberately
124                  * preserved on the expectation that it is better to preserve
125                  * needed memory than to discard unneeded memory.
126                  */
127                 start_index = (offset+(PAGE_SIZE-1)) >> PAGE_SHIFT;
128                 end_index = (endbyte >> PAGE_SHIFT);
129                 if ((endbyte & ~PAGE_MASK) != ~PAGE_MASK) {
130                         /* First page is tricky as 0 - 1 = -1, but pgoff_t
131                          * is unsigned, so the end_index >= start_index
132                          * check below would be true and we'll discard the whole
133                          * file cache which is not what was asked.
134                          */
135                         if (end_index == 0)
136                                 break;
137 
138                         end_index--;
139                 }
140 
141                 if (end_index >= start_index) {
142                         unsigned long count;
143 
144                         /*
145                          * It's common to FADV_DONTNEED right after
146                          * the read or write that instantiates the
147                          * pages, in which case there will be some
148                          * sitting on the local LRU cache. Try to
149                          * avoid the expensive remote drain and the
150                          * second cache tree walk below by flushing
151                          * them out right away.
152                          */
153                         lru_add_drain();
154 
155                         count = invalidate_mapping_pages(mapping,
156                                                 start_index, end_index);
157 
158                         /*
159                          * If fewer pages were invalidated than expected then
160                          * it is possible that some of the pages were on
161                          * a per-cpu pagevec for a remote CPU. Drain all
162                          * pagevecs and try again.
163                          */
164                         if (count < (end_index - start_index + 1)) {
165                                 lru_add_drain_all();
166                                 invalidate_mapping_pages(mapping, start_index,
167                                                 end_index);
168                         }
169                 }
170                 break;
171         default:
172                 ret = -EINVAL;
173         }
174 out:
175         fdput(f);
176         return ret;
177 }
178 
179 #ifdef __ARCH_WANT_SYS_FADVISE64
180 
181 SYSCALL_DEFINE4(fadvise64, int, fd, loff_t, offset, size_t, len, int, advice)
182 {
183         return sys_fadvise64_64(fd, offset, len, advice);
184 }
185 
186 #endif
187 

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