tmpfs: support SEEK_DATA and SEEK_HOLE (reprise)

[can-eth-gw-linux.git] / mm / shmem.c

diff --git a/mm/shmem.c b/mm/shmem.c
index 89341b658bd06b05d908f8becfef7fe0d904b808..03f9ba8fb8e543d96d2fad317a2a19126cf99222 100644 (file)
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -910,25 +910,29 @@ static struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
 static struct page *shmem_swapin(swp_entry_t swap, gfp_t gfp,
                        struct shmem_inode_info *info, pgoff_t index)
 {
-       struct mempolicy mpol, *spol;
        struct vm_area_struct pvma;
-
-       spol = mpol_cond_copy(&mpol,
-                       mpol_shared_policy_lookup(&info->policy, index));
+       struct page *page;
 
        /* Create a pseudo vma that just contains the policy */
        pvma.vm_start = 0;
        /* Bias interleave by inode number to distribute better across nodes */
        pvma.vm_pgoff = index + info->vfs_inode.i_ino;
        pvma.vm_ops = NULL;
-       pvma.vm_policy = spol;
-       return swapin_readahead(swap, gfp, &pvma, 0);
+       pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, index);
+
+       page = swapin_readahead(swap, gfp, &pvma, 0);
+
+       /* Drop reference taken by mpol_shared_policy_lookup() */
+       mpol_cond_put(pvma.vm_policy);
+
+       return page;
 }
 
 static struct page *shmem_alloc_page(gfp_t gfp,
                        struct shmem_inode_info *info, pgoff_t index)
 {
        struct vm_area_struct pvma;
+       struct page *page;
 
        /* Create a pseudo vma that just contains the policy */
        pvma.vm_start = 0;
@@ -937,10 +941,12 @@ static struct page *shmem_alloc_page(gfp_t gfp,
        pvma.vm_ops = NULL;
        pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, index);
 
-       /*
-        * alloc_page_vma() will drop the shared policy reference
-        */
-       return alloc_page_vma(gfp, &pvma, 0);
+       page = alloc_page_vma(gfp, &pvma, 0);
+
+       /* Drop reference taken by mpol_shared_policy_lookup() */
+       mpol_cond_put(pvma.vm_policy);
+
+       return page;
 }
 #else /* !CONFIG_NUMA */
 #ifdef CONFIG_TMPFS
@@ -1709,6 +1715,96 @@ static ssize_t shmem_file_splice_read(struct file *in, loff_t *ppos,
        return error;
 }
 
+/*
+ * llseek SEEK_DATA or SEEK_HOLE through the radix_tree.
+ */
+static pgoff_t shmem_seek_hole_data(struct address_space *mapping,
+                                   pgoff_t index, pgoff_t end, int origin)
+{
+       struct page *page;
+       struct pagevec pvec;
+       pgoff_t indices[PAGEVEC_SIZE];
+       bool done = false;
+       int i;
+
+       pagevec_init(&pvec, 0);
+       pvec.nr = 1;            /* start small: we may be there already */
+       while (!done) {
+               pvec.nr = shmem_find_get_pages_and_swap(mapping, index,
+                                       pvec.nr, pvec.pages, indices);
+               if (!pvec.nr) {
+                       if (origin == SEEK_DATA)
+                               index = end;
+                       break;
+               }
+               for (i = 0; i < pvec.nr; i++, index++) {
+                       if (index < indices[i]) {
+                               if (origin == SEEK_HOLE) {
+                                       done = true;
+                                       break;
+                               }
+                               index = indices[i];
+                       }
+                       page = pvec.pages[i];
+                       if (page && !radix_tree_exceptional_entry(page)) {
+                               if (!PageUptodate(page))
+                                       page = NULL;
+                       }
+                       if (index >= end ||
+                           (page && origin == SEEK_DATA) ||
+                           (!page && origin == SEEK_HOLE)) {
+                               done = true;
+                               break;
+                       }
+               }
+               shmem_deswap_pagevec(&pvec);
+               pagevec_release(&pvec);
+               pvec.nr = PAGEVEC_SIZE;
+               cond_resched();
+       }
+       return index;
+}
+
+static loff_t shmem_file_llseek(struct file *file, loff_t offset, int origin)
+{
+       struct address_space *mapping = file->f_mapping;
+       struct inode *inode = mapping->host;
+       pgoff_t start, end;
+       loff_t new_offset;
+
+       if (origin != SEEK_DATA && origin != SEEK_HOLE)
+               return generic_file_llseek_size(file, offset, origin,
+                                       MAX_LFS_FILESIZE, i_size_read(inode));
+       mutex_lock(&inode->i_mutex);
+       /* We're holding i_mutex so we can access i_size directly */
+
+       if (offset < 0)
+               offset = -EINVAL;
+       else if (offset >= inode->i_size)
+               offset = -ENXIO;
+       else {
+               start = offset >> PAGE_CACHE_SHIFT;
+               end = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
+               new_offset = shmem_seek_hole_data(mapping, start, end, origin);
+               new_offset <<= PAGE_CACHE_SHIFT;
+               if (new_offset > offset) {
+                       if (new_offset < inode->i_size)
+                               offset = new_offset;
+                       else if (origin == SEEK_DATA)
+                               offset = -ENXIO;
+                       else
+                               offset = inode->i_size;
+               }
+       }
+
+       if (offset >= 0 && offset != file->f_pos) {
+               file->f_pos = offset;
+               file->f_version = 0;
+       }
+       mutex_unlock(&inode->i_mutex);
+       return offset;
+}
+
 static long shmem_fallocate(struct file *file, int mode, loff_t offset,
                                                         loff_t len)
 {
@@ -2580,7 +2676,7 @@ static const struct address_space_operations shmem_aops = {
 static const struct file_operations shmem_file_operations = {
        .mmap           = shmem_mmap,
 #ifdef CONFIG_TMPFS
-       .llseek         = generic_file_llseek,
+       .llseek         = shmem_file_llseek,
        .read           = do_sync_read,
        .write          = do_sync_write,
        .aio_read       = shmem_file_aio_read,