With the write_begin/write_end aops, page_symlink was broken because it
could no longer pass a GFP_NOFS type mask into the point where the allocations
happened. They are done in write_begin, which would always assume that the
filesystem can be entered from reclaim. This bug could cause filesystem
deadlocks.
The funny thing with having a gfp_t mask there is that it doesn't really allow
the caller to arbitrarily tinker with the context in which it can be called.
It couldn't ever be GFP_ATOMIC, for example, because it needs to take the
page lock. The only thing any callers care about is __GFP_FS anyway, so turn
that into a single flag.
Add a new flag for write_begin, AOP_FLAG_NOFS. Filesystems can now act on
this flag in their write_begin function. Change __grab_cache_page to accept
a nofs argument as well, to honour that flag (while we're there, change the
name to grab_cache_page_write_begin which is more instructive and does away
with random leading underscores).
This is really a more flexible way to go in the end anyway -- if a filesystem
happens to want any extra allocations aside from the pagecache ones in ints
write_begin function, it may now use GFP_KERNEL (rather than GFP_NOFS) for
common case allocations (eg. ocfs2_alloc_write_ctxt, for a random example).
Signed-off-by: Nick Piggin <npiggin@xxxxxxx>
---
---
fs/affs/file.c | 2 +-
fs/afs/write.c | 2 +-
fs/buffer.c | 6 ++++--
fs/cifs/file.c | 3 ++-
fs/ecryptfs/mmap.c | 3 ++-
fs/ext3/inode.c | 3 ++-
fs/ext3/namei.c | 3 +--
fs/ext4/inode.c | 6 ++++--
fs/ext4/namei.c | 3 +--
fs/fuse/file.c | 3 ++-
fs/gfs2/ops_address.c | 3 ++-
fs/hostfs/hostfs_kern.c | 3 ++-
fs/jffs2/file.c | 3 ++-
fs/libfs.c | 3 ++-
fs/namei.c | 13 +++++++++----
fs/nfs/file.c | 3 ++-
fs/reiserfs/inode.c | 3 ++-
fs/smbfs/file.c | 3 ++-
fs/ubifs/file.c | 6 ++++--
include/linux/fs.h | 5 ++++-
include/linux/pagemap.h | 3 ++-
mm/filemap.c | 13 +++++++++----
22 files changed, 62 insertions(+), 33 deletions(-)
Index: linux-2.6/fs/namei.c
===================================================================
--- linux-2.6.orig/fs/namei.c
+++ linux-2.6/fs/namei.c
@@ -2786,18 +2786,23 @@ void page_put_link(struct dentry *dentry
}
}
-int __page_symlink(struct inode *inode, const char *symname, int len,
- gfp_t gfp_mask)
+/*
+ * The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS
+ */
+int __page_symlink(struct inode *inode, const char *symname, int len, int nofs)
{
struct address_space *mapping = inode->i_mapping;
struct page *page;
void *fsdata;
int err;
char *kaddr;
+ unsigned int flags = AOP_FLAG_UNINTERRUPTIBLE;
+ if (nofs)
+ flags |= AOP_FLAG_NOFS;
retry:
err = pagecache_write_begin(NULL, mapping, 0, len-1,
- AOP_FLAG_UNINTERRUPTIBLE, &page, &fsdata);
+ flags, &page, &fsdata);
if (err)
goto fail;
@@ -2821,7 +2826,7 @@ fail:
int page_symlink(struct inode *inode, const char *symname, int len)
{
return __page_symlink(inode, symname, len,
- mapping_gfp_mask(inode->i_mapping));
+ !(mapping_gfp_mask(inode->i_mapping) & __GFP_FS));
}
const struct inode_operations page_symlink_inode_operations = {
Index: linux-2.6/include/linux/fs.h
===================================================================
--- linux-2.6.orig/include/linux/fs.h
+++ linux-2.6/include/linux/fs.h
@@ -414,6 +414,9 @@ enum positive_aop_returns {
#define AOP_FLAG_UNINTERRUPTIBLE 0x0001 /* will not do a short write */
#define AOP_FLAG_CONT_EXPAND 0x0002 /* called from cont_expand */
+#define AOP_FLAG_NOFS 0x0004 /* used by filesystem to direct
+ * helper code (eg buffer layer)
+ * to clear GFP_FS from alloc */
/*
* oh the beauties of C type declarations.
@@ -2023,7 +2026,7 @@ extern int page_readlink(struct dentry *
extern void *page_follow_link_light(struct dentry *, struct nameidata *);
extern void page_put_link(struct dentry *, struct nameidata *, void *);
extern int __page_symlink(struct inode *inode, const char *symname, int len,
- gfp_t gfp_mask);
+ int nofs);
extern int page_symlink(struct inode *inode, const char *symname, int len);
extern const struct inode_operations page_symlink_inode_operations;
extern int generic_readlink(struct dentry *, char __user *, int);
Index: linux-2.6/fs/ext3/namei.c
===================================================================
--- linux-2.6.orig/fs/ext3/namei.c
+++ linux-2.6/fs/ext3/namei.c
@@ -2170,8 +2170,7 @@ retry:
* We have a transaction open. All is sweetness. It also sets
* i_size in generic_commit_write().
*/
- err = __page_symlink(inode, symname, l,
- mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS);
+ err = __page_symlink(inode, symname, l, 1);
if (err) {
drop_nlink(inode);
ext3_mark_inode_dirty(handle, inode);
Index: linux-2.6/fs/ext4/namei.c
===================================================================
--- linux-2.6.orig/fs/ext4/namei.c
+++ linux-2.6/fs/ext4/namei.c
@@ -2208,8 +2208,7 @@ retry:
* We have a transaction open. All is sweetness. It also sets
* i_size in generic_commit_write().
*/
- err = __page_symlink(inode, symname, l,
- mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS);
+ err = __page_symlink(inode, symname, l, 1);
if (err) {
clear_nlink(inode);
ext4_mark_inode_dirty(handle, inode);
Index: linux-2.6/include/linux/pagemap.h
===================================================================
--- linux-2.6.orig/include/linux/pagemap.h
+++ linux-2.6/include/linux/pagemap.h
@@ -241,7 +241,8 @@ unsigned find_get_pages_contig(struct ad
unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
int tag, unsigned int nr_pages, struct page **pages);
-struct page *__grab_cache_page(struct address_space *mapping, pgoff_t index);
+struct page *grab_cache_page_write_begin(struct address_space *mapping,
+ pgoff_t index, int nofs);
/*
* Returns locked page at given index in given cache, creating it if needed.
Index: linux-2.6/mm/filemap.c
===================================================================
--- linux-2.6.orig/mm/filemap.c
+++ linux-2.6/mm/filemap.c
@@ -2147,19 +2147,24 @@ EXPORT_SYMBOL(generic_file_direct_write)
* Find or create a page at the given pagecache position. Return the locked
* page. This function is specifically for buffered writes.
*/
-struct page *__grab_cache_page(struct address_space *mapping, pgoff_t index)
+struct page *grab_cache_page_write_begin(struct address_space *mapping,
+ pgoff_t index, int nofs)
{
int status;
struct page *page;
+ gfp_t gfp_notmask = 0;
+ if (nofs)
+ gfp_notmask = __GFP_FS;
repeat:
page = find_lock_page(mapping, index);
if (likely(page))
return page;
- page = page_cache_alloc(mapping);
+ page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~gfp_notmask);
if (!page)
return NULL;
- status = add_to_page_cache_lru(page, mapping, index, GFP_KERNEL);
+ status = add_to_page_cache_lru(page, mapping, index,
+ GFP_KERNEL & ~gfp_notmask);
if (unlikely(status)) {
page_cache_release(page);
if (status == -EEXIST)
@@ -2168,7 +2173,7 @@ repeat:
}
return page;
}
-EXPORT_SYMBOL(__grab_cache_page);
+EXPORT_SYMBOL(grab_cache_page_write_begin);
static ssize_t generic_perform_write(struct file *file,
struct iov_iter *i, loff_t pos)
Index: linux-2.6/fs/affs/file.c
===================================================================
--- linux-2.6.orig/fs/affs/file.c
+++ linux-2.6/fs/affs/file.c
@@ -628,7 +628,7 @@ static int affs_write_begin_ofs(struct f
}
index = pos >> PAGE_CACHE_SHIFT;
- page = __grab_cache_page(mapping, index);
+ page = grab_cache_page_write_begin(mapping, index, flags&AOP_FLAG_NOFS);
if (!page)
return -ENOMEM;
*pagep = page;
Index: linux-2.6/fs/afs/write.c
===================================================================
--- linux-2.6.orig/fs/afs/write.c
+++ linux-2.6/fs/afs/write.c
@@ -144,7 +144,7 @@ int afs_write_begin(struct file *file, s
candidate->state = AFS_WBACK_PENDING;
init_waitqueue_head(&candidate->waitq);
- page = __grab_cache_page(mapping, index);
+ page = grab_cache_page_write_begin(mapping, index, flags&AOP_FLAG_NOFS);
if (!page) {
kfree(candidate);
return -ENOMEM;
Index: linux-2.6/fs/buffer.c
===================================================================
--- linux-2.6.orig/fs/buffer.c
+++ linux-2.6/fs/buffer.c
@@ -1988,7 +1988,8 @@ int block_write_begin(struct file *file,
page = *pagep;
if (page == NULL) {
ownpage = 1;
- page = __grab_cache_page(mapping, index);
+ page = grab_cache_page_write_begin(mapping, index,
+ flags & AOP_FLAG_NOFS);
if (!page) {
status = -ENOMEM;
goto out;
@@ -2494,7 +2495,8 @@ int nobh_write_begin(struct file *file,
from = pos & (PAGE_CACHE_SIZE - 1);
to = from + len;
- page = __grab_cache_page(mapping, index);
+ page = grab_cache_page_write_begin(mapping, index,
+ flags & AOP_FLAG_NOFS);
if (!page)
return -ENOMEM;
*pagep = page;
Index: linux-2.6/fs/cifs/file.c
===================================================================
--- linux-2.6.orig/fs/cifs/file.c
+++ linux-2.6/fs/cifs/file.c
@@ -2073,7 +2073,8 @@ static int cifs_write_begin(struct file
cFYI(1, ("write_begin from %lld len %d", (long long)pos, len));
- page = __grab_cache_page(mapping, index);
+ page = grab_cache_page_write_begin(mapping, index,
+ flags & AOP_FLAG_NOFS);
if (!page) {
rc = -ENOMEM;
goto out;
Index: linux-2.6/fs/ecryptfs/mmap.c
===================================================================
--- linux-2.6.orig/fs/ecryptfs/mmap.c
+++ linux-2.6/fs/ecryptfs/mmap.c
@@ -288,7 +288,8 @@ static int ecryptfs_write_begin(struct f
loff_t prev_page_end_size;
int rc = 0;
- page = __grab_cache_page(mapping, index);
+ page = grab_cache_page_write_begin(mapping, index,
+ flags & AOP_FLAG_NOFS);
if (!page)
return -ENOMEM;
*pagep = page;
Index: linux-2.6/fs/ext3/inode.c
===================================================================
--- linux-2.6.orig/fs/ext3/inode.c
+++ linux-2.6/fs/ext3/inode.c
@@ -1160,7 +1160,8 @@ static int ext3_write_begin(struct file
to = from + len;
retry:
- page = __grab_cache_page(mapping, index);
+ page = grab_cache_page_write_begin(mapping, index,
+ flags & AOP_FLAG_NOFS);
if (!page)
return -ENOMEM;
*pagep = page;
Index: linux-2.6/fs/ext4/inode.c
===================================================================
--- linux-2.6.orig/fs/ext4/inode.c
+++ linux-2.6/fs/ext4/inode.c
@@ -1345,7 +1345,8 @@ retry:
goto out;
}
- page = __grab_cache_page(mapping, index);
+ page = grab_cache_page_write_begin(mapping, index,
+ flags & AOP_FLAG_NOFS);
if (!page) {
ext4_journal_stop(handle);
ret = -ENOMEM;
@@ -2549,7 +2550,8 @@ retry:
goto out;
}
- page = __grab_cache_page(mapping, index);
+ page = grab_cache_page_write_begin(mapping, index,
+ flags & AOP_FLAG_NOFS);
if (!page) {
ext4_journal_stop(handle);
ret = -ENOMEM;
Index: linux-2.6/fs/fuse/file.c
===================================================================
--- linux-2.6.orig/fs/fuse/file.c
+++ linux-2.6/fs/fuse/file.c
@@ -646,7 +646,8 @@ static int fuse_write_begin(struct file
{
pgoff_t index = pos >> PAGE_CACHE_SHIFT;
- *pagep = __grab_cache_page(mapping, index);
+ *pagep = grab_cache_page_write_begin(mapping, index,
+ flags & AOP_FLAG_NOFS);
if (!*pagep)
return -ENOMEM;
return 0;
Index: linux-2.6/fs/gfs2/ops_address.c
===================================================================
--- linux-2.6.orig/fs/gfs2/ops_address.c
+++ linux-2.6/fs/gfs2/ops_address.c
@@ -675,7 +675,8 @@ static int gfs2_write_begin(struct file
goto out_trans_fail;
error = -ENOMEM;
- page = __grab_cache_page(mapping, index);
+ page = grab_cache_page_write_begin(mapping, index,
+ flags & AOP_FLAG_NOFS);
*pagep = page;
if (unlikely(!page))
goto out_endtrans;
Index: linux-2.6/fs/hostfs/hostfs_kern.c
===================================================================
--- linux-2.6.orig/fs/hostfs/hostfs_kern.c
+++ linux-2.6/fs/hostfs/hostfs_kern.c
@@ -501,7 +501,8 @@ int hostfs_write_begin(struct file *file
{
pgoff_t index = pos >> PAGE_CACHE_SHIFT;
- *pagep = __grab_cache_page(mapping, index);
+ *pagep = grab_cache_page_write_begin(mapping, index,
+ flags & AOP_FLAG_NOFS);
if (!*pagep)
return -ENOMEM;
return 0;
Index: linux-2.6/fs/jffs2/file.c
===================================================================
--- linux-2.6.orig/fs/jffs2/file.c
+++ linux-2.6/fs/jffs2/file.c
@@ -132,7 +132,8 @@ static int jffs2_write_begin(struct file
uint32_t pageofs = index << PAGE_CACHE_SHIFT;
int ret = 0;
- pg = __grab_cache_page(mapping, index);
+ pg = grab_cache_page_write_begin(mapping, index,
+ flags & AOP_FLAG_NOFS);
if (!pg)
return -ENOMEM;
*pagep = pg;
Index: linux-2.6/fs/libfs.c
===================================================================
--- linux-2.6.orig/fs/libfs.c
+++ linux-2.6/fs/libfs.c
@@ -360,7 +360,8 @@ int simple_write_begin(struct file *file
index = pos >> PAGE_CACHE_SHIFT;
from = pos & (PAGE_CACHE_SIZE - 1);
- page = __grab_cache_page(mapping, index);
+ page = grab_cache_page_write_begin(mapping, index,
+ flags & AOP_FLAG_NOFS);
if (!page)
return -ENOMEM;
Index: linux-2.6/fs/nfs/file.c
===================================================================
--- linux-2.6.orig/fs/nfs/file.c
+++ linux-2.6/fs/nfs/file.c
@@ -354,7 +354,8 @@ static int nfs_write_begin(struct file *
file->f_path.dentry->d_name.name,
mapping->host->i_ino, len, (long long) pos);
- page = __grab_cache_page(mapping, index);
+ page = grab_cache_page_write_begin(mapping, index,
+ flags & AOP_FLAG_NOFS);
if (!page)
return -ENOMEM;
*pagep = page;
Index: linux-2.6/fs/reiserfs/inode.c
===================================================================
--- linux-2.6.orig/fs/reiserfs/inode.c
+++ linux-2.6/fs/reiserfs/inode.c
@@ -2556,7 +2556,8 @@ static int reiserfs_write_begin(struct f
}
index = pos >> PAGE_CACHE_SHIFT;
- page = __grab_cache_page(mapping, index);
+ page = grab_cache_page_write_begin(mapping, index,
+ flags & AOP_FLAG_NOFS);
if (!page)
return -ENOMEM;
*pagep = page;
Index: linux-2.6/fs/smbfs/file.c
===================================================================
--- linux-2.6.orig/fs/smbfs/file.c
+++ linux-2.6/fs/smbfs/file.c
@@ -297,7 +297,8 @@ static int smb_write_begin(struct file *
struct page **pagep, void **fsdata)
{
pgoff_t index = pos >> PAGE_CACHE_SHIFT;
- *pagep = __grab_cache_page(mapping, index);
+ *pagep = grab_cache_page_write_begin(mapping, index,
+ flags & AOP_FLAG_NOFS);
if (!*pagep)
return -ENOMEM;
return 0;
Index: linux-2.6/fs/ubifs/file.c
===================================================================
--- linux-2.6.orig/fs/ubifs/file.c
+++ linux-2.6/fs/ubifs/file.c
@@ -247,7 +247,8 @@ static int write_begin_slow(struct addre
if (unlikely(err))
return err;
- page = __grab_cache_page(mapping, index);
+ page = grab_cache_page_write_begin(mapping, index,
+ flags & AOP_FLAG_NOFS);
if (unlikely(!page)) {
ubifs_release_budget(c, &req);
return -ENOMEM;
@@ -438,7 +439,8 @@ static int ubifs_write_begin(struct file
return -EROFS;
/* Try out the fast-path part first */
- page = __grab_cache_page(mapping, index);
+ page = grab_cache_page_write_begin(mapping, index,
+ flags & AOP_FLAG_NOFS);
if (unlikely(!page))
return -ENOMEM;
--
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