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Message-ID: <20061130072247.GC18004@wotan.suse.de>
Date: Thu, 30 Nov 2006 08:22:47 +0100
From: Nick Piggin <npiggin@...e.de>
To: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Andrew Morton <akpm@...l.org>, linux-fsdevel@...r.kernel.org
Subject: [patch 3/3] fs: fix cont vs deadlock patches
Rework the cont filesystem helpers so that generic_cont_expand does the
actual work of expanding the file. cont_prepare_write then calls this
routine if expanding is needed, and retries. Also solves the problem
where cont_prepare_write would previously hold the target page locked
while doing not-very-nice things like locking other pages.
Means that zero-length prepare/commit_write pairs are no longer needed
as an overloaded directive to extend the file, thus cont should operate
better within the new deadlock-free buffered write code.
Converts fat over to the new cont scheme.
Signed-off-by: Nick Piggin <npiggin@...e.de>
Index: linux-2.6/fs/buffer.c
===================================================================
--- linux-2.6.orig/fs/buffer.c
+++ linux-2.6/fs/buffer.c
@@ -2004,19 +2004,20 @@ int block_read_full_page(struct page *pa
return 0;
}
-/* utility function for filesystems that need to do work on expanding
- * truncates. Uses prepare/commit_write to allow the filesystem to
- * deal with the hole.
+/*
+ * Utility function for filesystems that need to do work on expanding
+ * truncates. For moronic filesystems that do not allow holes in file.
*/
-static int __generic_cont_expand(struct inode *inode, loff_t size,
- pgoff_t index, unsigned int offset)
+int generic_cont_expand(struct inode *inode, loff_t size, loff_t *bytes,
+ get_block_t *get_block)
{
struct address_space *mapping = inode->i_mapping;
+ unsigned long blocksize = 1 << inode->i_blkbits;
struct page *page;
unsigned long limit;
- int err;
+ int status;
- err = -EFBIG;
+ status = -EFBIG;
limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
if (limit != RLIM_INFINITY && size > (loff_t)limit) {
send_sig(SIGXFSZ, current, 0);
@@ -2025,146 +2026,83 @@ static int __generic_cont_expand(struct
if (size > inode->i_sb->s_maxbytes)
goto out;
- err = -ENOMEM;
- page = grab_cache_page(mapping, index);
- if (!page)
- goto out;
- err = mapping->a_ops->prepare_write(NULL, page, offset, offset);
- if (err) {
- /*
- * ->prepare_write() may have instantiated a few blocks
- * outside i_size. Trim these off again.
- */
- unlock_page(page);
- page_cache_release(page);
- vmtruncate(inode, inode->i_size);
- goto out;
- }
+ status = 0;
- err = mapping->a_ops->commit_write(NULL, page, offset, offset);
+ while (*bytes < size) {
+ unsigned int zerofrom;
+ unsigned int zeroto;
+ void *kaddr;
+ pgoff_t pgpos;
+
+ pgpos = *bytes >> PAGE_CACHE_SHIFT;
+ page = grab_cache_page(mapping, pgpos);
+ if (!page) {
+ status = -ENOMEM;
+ break;
+ }
+ /* we might sleep */
+ if (*bytes >> PAGE_CACHE_SHIFT != pgpos)
+ goto unlock;
- unlock_page(page);
- page_cache_release(page);
- if (err > 0)
- err = 0;
-out:
- return err;
-}
+ zerofrom = *bytes & ~PAGE_CACHE_MASK;
+ if (zerofrom & (blocksize-1))
+ *bytes = (*bytes + blocksize-1) & (blocksize-1);
-int generic_cont_expand(struct inode *inode, loff_t size)
-{
- pgoff_t index;
- unsigned int offset;
+ zeroto = PAGE_CACHE_SIZE;
- offset = (size & (PAGE_CACHE_SIZE - 1)); /* Within page */
+ status = __block_prepare_write(inode, page, zerofrom,
+ zeroto, get_block);
+ if (status)
+ goto unlock;
+ kaddr = kmap_atomic(page, KM_USER0);
+ memset(kaddr+zerofrom, 0, PAGE_CACHE_SIZE-zerofrom);
+ flush_dcache_page(page);
+ kunmap_atomic(kaddr, KM_USER0);
+ status = __block_commit_write(inode, page, zerofrom, zeroto);
- /* ugh. in prepare/commit_write, if from==to==start of block, we
- ** skip the prepare. make sure we never send an offset for the start
- ** of a block
- */
- if ((offset & (inode->i_sb->s_blocksize - 1)) == 0) {
- /* caller must handle this extra byte. */
- offset++;
+unlock:
+ unlock_page(page);
+ page_cache_release(page);
+ if (status) {
+ BUG_ON(status == AOP_TRUNCATED_PAGE);
+ break;
+ }
}
- index = size >> PAGE_CACHE_SHIFT;
- return __generic_cont_expand(inode, size, index, offset);
-}
-
-int generic_cont_expand_simple(struct inode *inode, loff_t size)
-{
- loff_t pos = size - 1;
- pgoff_t index = pos >> PAGE_CACHE_SHIFT;
- unsigned int offset = (pos & (PAGE_CACHE_SIZE - 1)) + 1;
+ /*
+ * No need to use i_size_read() here, the i_size
+ * cannot change under us because we hold i_mutex.
+ */
+ if (size > inode->i_size) {
+ i_size_write(inode, size);
+ mark_inode_dirty(inode);
+ }
- /* prepare/commit_write can handle even if from==to==start of block. */
- return __generic_cont_expand(inode, size, index, offset);
+out:
+ return status;
}
-/*
- * For moronic filesystems that do not allow holes in file.
- * We may have to extend the file.
- */
-
int cont_prepare_write(struct page *page, unsigned offset,
unsigned to, get_block_t *get_block, loff_t *bytes)
{
- struct address_space *mapping = page->mapping;
- struct inode *inode = mapping->host;
- struct page *new_page;
- pgoff_t pgpos;
- long status;
- unsigned zerofrom;
- unsigned blocksize = 1 << inode->i_blkbits;
- void *kaddr;
-
- while(page->index > (pgpos = *bytes>>PAGE_CACHE_SHIFT)) {
- status = -ENOMEM;
- new_page = grab_cache_page(mapping, pgpos);
- if (!new_page)
- goto out;
- /* we might sleep */
- if (*bytes>>PAGE_CACHE_SHIFT != pgpos) {
- unlock_page(new_page);
- page_cache_release(new_page);
- continue;
- }
- zerofrom = *bytes & ~PAGE_CACHE_MASK;
- if (zerofrom & (blocksize-1)) {
- *bytes |= (blocksize-1);
- (*bytes)++;
- }
- status = __block_prepare_write(inode, new_page, zerofrom,
- PAGE_CACHE_SIZE, get_block);
- if (status)
- goto out_unmap;
- kaddr = kmap_atomic(new_page, KM_USER0);
- memset(kaddr+zerofrom, 0, PAGE_CACHE_SIZE-zerofrom);
- flush_dcache_page(new_page);
- kunmap_atomic(kaddr, KM_USER0);
- generic_commit_write(NULL, new_page, zerofrom, PAGE_CACHE_SIZE);
- unlock_page(new_page);
- page_cache_release(new_page);
- }
-
- if (page->index < pgpos) {
- /* completely inside the area */
- zerofrom = offset;
- } else {
- /* page covers the boundary, find the boundary offset */
- zerofrom = *bytes & ~PAGE_CACHE_MASK;
-
- /* if we will expand the thing last block will be filled */
- if (to > zerofrom && (zerofrom & (blocksize-1))) {
- *bytes |= (blocksize-1);
- (*bytes)++;
- }
+ loff_t size = (page->index << PAGE_CACHE_SHIFT) + offset;
+ struct inode *inode = page->mapping->host;
+ int err;
- /* starting below the boundary? Nothing to zero out */
- if (offset <= zerofrom)
- zerofrom = offset;
- }
- status = __block_prepare_write(inode, page, zerofrom, to, get_block);
- if (status)
- goto out1;
- if (zerofrom < offset) {
- kaddr = kmap_atomic(page, KM_USER0);
- memset(kaddr+zerofrom, 0, offset-zerofrom);
- flush_dcache_page(page);
- kunmap_atomic(kaddr, KM_USER0);
- __block_commit_write(inode, page, zerofrom, offset);
+ if (*bytes < size) {
+ unlock_page(page);
+ err = generic_cont_expand(inode, size, bytes, get_block);
+ if (!err)
+ err = AOP_TRUNCATED_PAGE;
+ else
+ lock_page(page); /* caller expects this */
+ return err;
}
- return 0;
-out1:
- ClearPageUptodate(page);
- return status;
-out_unmap:
- ClearPageUptodate(new_page);
- unlock_page(new_page);
- page_cache_release(new_page);
-out:
- return status;
+ err = __block_prepare_write(inode, page, offset, to, get_block);
+ if (err)
+ ClearPageUptodate(page);
+ return err;
}
int block_prepare_write(struct page *page, unsigned from, unsigned to,
@@ -3015,7 +2953,6 @@ EXPORT_SYMBOL(fsync_bdev);
EXPORT_SYMBOL(generic_block_bmap);
EXPORT_SYMBOL(generic_commit_write);
EXPORT_SYMBOL(generic_cont_expand);
-EXPORT_SYMBOL(generic_cont_expand_simple);
EXPORT_SYMBOL(init_buffer);
EXPORT_SYMBOL(invalidate_bdev);
EXPORT_SYMBOL(ll_rw_block);
Index: linux-2.6/include/linux/buffer_head.h
===================================================================
--- linux-2.6.orig/include/linux/buffer_head.h
+++ linux-2.6/include/linux/buffer_head.h
@@ -202,8 +202,7 @@ int block_read_full_page(struct page*, g
int block_prepare_write(struct page*, unsigned, unsigned, get_block_t*);
int cont_prepare_write(struct page*, unsigned, unsigned, get_block_t*,
loff_t *);
-int generic_cont_expand(struct inode *inode, loff_t size);
-int generic_cont_expand_simple(struct inode *inode, loff_t size);
+int generic_cont_expand(struct inode *inode, loff_t size, loff_t *bytes, get_block_t *);
int block_commit_write(struct page *page, unsigned from, unsigned to);
void block_sync_page(struct page *);
sector_t generic_block_bmap(struct address_space *, sector_t, get_block_t *);
Index: linux-2.6/fs/fat/inode.c
===================================================================
--- linux-2.6.orig/fs/fat/inode.c
+++ linux-2.6/fs/fat/inode.c
@@ -151,11 +151,12 @@ static int fat_commit_write(struct file
{
struct inode *inode = page->mapping->host;
int err;
- if (to - from > 0)
- return 0;
err = generic_commit_write(file, page, from, to);
- if (!err && !(MSDOS_I(inode)->i_attrs & ATTR_ARCH)) {
+ if (err)
+ return err;
+
+ if (!(MSDOS_I(inode)->i_attrs & ATTR_ARCH)) {
inode->i_mtime = inode->i_ctime = CURRENT_TIME_SEC;
MSDOS_I(inode)->i_attrs |= ATTR_ARCH;
mark_inode_dirty(inode);
-
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