From: Hugh Dickins <hugh@veritas.com>
To: Andrew Morton <akpm@digeo.com>
Cc: Christoph Rohland <cr@sap.com>, <linux-kernel@vger.kernel.org>
Subject: [PATCH] tmpfs 4/9 shmem_getpage locked
Date: Tue, 1 Oct 2002 22:48:45 +0100 (BST) [thread overview]
Message-ID: <Pine.LNX.4.44.0210012247520.2602-100000@localhost.localdomain> (raw)
In-Reply-To: <Pine.LNX.4.44.0210012240470.2602-100000@localhost.localdomain>
The distinction between shmem_getpage and shmem_getpage_locked is
not helpful, particularly now info->sem is gone; and shmem_getpage
confusingly tailored to shmem_nopage's expectations. Put the code
of shmem_getpage_locked into the frame of shmem_getpage, leaving
its callers to unlock_page afterwards.
--- tmpfs3/mm/shmem.c Tue Oct 1 19:49:04 2002
+++ tmpfs4/mm/shmem.c Tue Oct 1 19:49:09 2002
@@ -495,10 +495,6 @@
/*
* Move the page from the page cache to the swap cache.
- *
- * The page lock prevents multiple occurences of shmem_writepage at
- * once. We still need to guard against racing with
- * shmem_getpage_locked().
*/
static int shmem_writepage(struct page * page)
{
@@ -560,19 +556,16 @@
}
/*
- * shmem_getpage_locked - either get the page from swap or allocate a new one
+ * shmem_getpage - either get the page from swap or allocate a new one
*
* If we allocate a new one we do not mark it dirty. That's up to the
* vm. If we swap it in we mark it dirty since we also free the swap
* entry since a page cannot live in both the swap and page cache
- *
- * Called with the inode locked, so it cannot race with itself, but we
- * still need to guard against racing with shm_writepage(), which might
- * be trying to move the page to the swap cache as we run.
*/
-static struct page * shmem_getpage_locked(struct shmem_inode_info *info, struct inode * inode, unsigned long idx)
+static int shmem_getpage(struct inode *inode, unsigned long idx, struct page **pagep)
{
struct address_space *mapping = inode->i_mapping;
+ struct shmem_inode_info *info = SHMEM_I(inode);
struct shmem_sb_info *sbinfo;
struct page *page;
swp_entry_t *entry;
@@ -580,7 +573,7 @@
int error = 0;
if (idx >= SHMEM_MAX_INDEX)
- return ERR_PTR(-EFBIG);
+ return -EFBIG;
/*
* When writing, i_sem is held against truncation and other
@@ -595,15 +588,17 @@
repeat:
page = find_lock_page(mapping, idx);
- if (page)
- return page;
+ if (page) {
+ *pagep = page;
+ return 0;
+ }
spin_lock(&info->lock);
shmem_recalc_inode(inode);
entry = shmem_swp_alloc(info, idx);
if (IS_ERR(entry)) {
spin_unlock(&info->lock);
- return (void *)entry;
+ return PTR_ERR(entry);
}
swap = *entry;
@@ -623,7 +618,7 @@
error = -ENOMEM;
spin_unlock(&info->lock);
if (error)
- return ERR_PTR(error);
+ return error;
goto repeat;
}
wait_on_page_locked(page);
@@ -652,7 +647,7 @@
spin_unlock(&info->lock);
unlock_page(page);
page_cache_release(page);
- return ERR_PTR(error);
+ return error;
}
*entry = (swp_entry_t) {0};
@@ -665,7 +660,7 @@
spin_lock(&sbinfo->stat_lock);
if (sbinfo->free_blocks == 0) {
spin_unlock(&sbinfo->stat_lock);
- return ERR_PTR(-ENOSPC);
+ return -ENOSPC;
}
sbinfo->free_blocks--;
spin_unlock(&sbinfo->stat_lock);
@@ -675,7 +670,7 @@
spin_lock(&sbinfo->stat_lock);
sbinfo->free_blocks++;
spin_unlock(&sbinfo->stat_lock);
- return ERR_PTR(-ENOMEM);
+ return -ENOMEM;
}
spin_lock(&info->lock);
@@ -690,7 +685,7 @@
sbinfo->free_blocks++;
spin_unlock(&sbinfo->stat_lock);
if (error)
- return ERR_PTR(error);
+ return error;
goto repeat;
}
spin_unlock(&info->lock);
@@ -700,30 +695,8 @@
/* We have the page */
SetPageUptodate(page);
- return page;
-}
-
-static int shmem_getpage(struct inode * inode, unsigned long idx, struct page **ptr)
-{
- struct shmem_inode_info *info = SHMEM_I(inode);
- int error;
-
- *ptr = ERR_PTR(-EFAULT);
- if (inode->i_size <= (loff_t) idx * PAGE_CACHE_SIZE)
- goto failed;
-
- *ptr = shmem_getpage_locked(info, inode, idx);
- if (IS_ERR (*ptr))
- goto failed;
-
- unlock_page(*ptr);
+ *pagep = page;
return 0;
-failed:
- error = PTR_ERR(*ptr);
- *ptr = NOPAGE_SIGBUS;
- if (error == -ENOMEM)
- *ptr = NOPAGE_OOM;
- return error;
}
static struct page *shmem_holdpage(struct inode *inode, unsigned long idx)
@@ -747,26 +720,32 @@
}
spin_unlock(&info->lock);
if (swap.val) {
- if (shmem_getpage(inode, idx, &page) < 0)
- page = NULL;
+ if (shmem_getpage(inode, idx, &page) == 0)
+ unlock_page(page);
}
return page;
}
-struct page * shmem_nopage(struct vm_area_struct * vma, unsigned long address, int unused)
+struct page *shmem_nopage(struct vm_area_struct *vma, unsigned long address, int unused)
{
- struct page * page;
- unsigned int idx;
- struct inode * inode = vma->vm_file->f_dentry->d_inode;
+ struct inode *inode = vma->vm_file->f_dentry->d_inode;
+ struct page *page;
+ unsigned long idx;
+ int error;
idx = (address - vma->vm_start) >> PAGE_CACHE_SHIFT;
idx += vma->vm_pgoff;
- if (shmem_getpage(inode, idx, &page))
- return page;
+ if (((loff_t) idx << PAGE_CACHE_SHIFT) >= inode->i_size)
+ return NOPAGE_SIGBUS;
+ error = shmem_getpage(inode, idx, &page);
+ if (error)
+ return (error == -ENOMEM)? NOPAGE_OOM: NOPAGE_SIGBUS;
+
+ unlock_page(page);
flush_page_to_ram(page);
- return(page);
+ return page;
}
void shmem_lock(struct file * file, int lock)
@@ -882,7 +861,6 @@
shmem_file_write(struct file *file,const char *buf,size_t count,loff_t *ppos)
{
struct inode *inode = file->f_dentry->d_inode;
- struct shmem_inode_info *info;
unsigned long limit = current->rlim[RLIMIT_FSIZE].rlim_cur;
loff_t pos;
struct page *page;
@@ -973,11 +951,8 @@
__get_user(dummy, buf+bytes-1);
}
- info = SHMEM_I(inode);
- page = shmem_getpage_locked(info, inode, index);
-
- status = PTR_ERR(page);
- if (IS_ERR(page))
+ status = shmem_getpage(inode, index, &page);
+ if (status)
break;
/* We have exclusive IO access to the page.. */
@@ -1064,10 +1039,12 @@
if (index == end_index) {
nr = inode->i_size & ~PAGE_CACHE_MASK;
if (nr <= offset) {
+ unlock_page(page);
page_cache_release(page);
break;
}
}
+ unlock_page(page);
nr -= offset;
if (!list_empty(&mapping->i_mmap_shared))
@@ -1271,6 +1248,7 @@
static int shmem_symlink(struct inode * dir, struct dentry *dentry, const char * symname)
{
+ int error;
int len;
struct inode *inode;
struct page *page;
@@ -1296,11 +1274,11 @@
iput(inode);
return -ENOMEM;
}
- page = shmem_getpage_locked(info, inode, 0);
- if (IS_ERR(page)) {
+ error = shmem_getpage(inode, 0, &page);
+ if (error) {
vm_unacct_memory(VM_ACCT(1));
iput(inode);
- return PTR_ERR(page);
+ return error;
}
inode->i_op = &shmem_symlink_inode_operations;
spin_lock (&shmem_ilock);
@@ -1332,27 +1310,26 @@
static int shmem_readlink(struct dentry *dentry, char *buffer, int buflen)
{
- struct page * page;
+ struct page *page;
int res = shmem_getpage(dentry->d_inode, 0, &page);
-
if (res)
return res;
-
- res = vfs_readlink(dentry,buffer,buflen, kmap(page));
+ res = vfs_readlink(dentry, buffer, buflen, kmap(page));
kunmap(page);
+ unlock_page(page);
page_cache_release(page);
return res;
}
static int shmem_follow_link(struct dentry *dentry, struct nameidata *nd)
{
- struct page * page;
+ struct page *page;
int res = shmem_getpage(dentry->d_inode, 0, &page);
if (res)
return res;
-
res = vfs_follow_link(nd, kmap(page));
kunmap(page);
+ unlock_page(page);
page_cache_release(page);
return res;
}
next prev parent reply other threads:[~2002-10-01 21:42 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-10-01 21:44 [PATCH] tmpfs 1/9 shmem_vm_writeback Hugh Dickins
2002-10-01 21:46 ` [PATCH] tmpfs 2/9 partial shmem_holdpage Hugh Dickins
2002-10-01 21:47 ` [PATCH] tmpfs 3/9 remove info->sem Hugh Dickins
2002-10-01 21:48 ` Hugh Dickins [this message]
2002-10-01 21:50 ` [PATCH] tmpfs 5/9 shmem_free_block alloced Hugh Dickins
2002-10-01 21:51 ` [PATCH] tmpfs 6/9 highmem metadata Hugh Dickins
2002-10-01 21:53 ` [PATCH] tmpfs 7/9 shmem_swp_set nr_swapped Hugh Dickins
2002-10-01 21:54 ` [PATCH] tmpfs 8/9 misc trivia Hugh Dickins
2002-10-01 21:55 ` [PATCH] tmpfs 9/9 whitespace only Hugh Dickins
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