diff options
author | Chris Mason <mason@suse.com> | 2005-01-04 05:34:52 -0800 |
---|---|---|
committer | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-01-04 05:34:52 -0800 |
commit | a61e72861942fa9405a5600b26ee6bcf4872c248 (patch) | |
tree | feee4ed207f4c658c57f35c0810050b5f78fd3df /fs | |
parent | 5d25c798a71097371cc4e035fe6aa6fdfd7b63d5 (diff) | |
download | history-a61e72861942fa9405a5600b26ee6bcf4872c248.tar.gz |
[PATCH] __getblk_slow can loop forever when pages are partially mapped
When a block device is accessed via read/write, it is possible for some of
the buffers on a page to be mapped and others not. __getblk and friends
assume this can't happen, and can end up looping forever when pages have
some unmapped buffers. Picture:
lseek(/dev/xxx, 2048, SEEK_SET)
write(/dev/xxx, 2048 bytes)
Assuming the block size is 1k, page 0 has 4 buffers, two are mapped by
__block_prepare_write and two are not. Next, another process triggers
getblk(/dev/xxx, blocknr = 0);
__getblk_slow will loop forever. __find_get_block fails because the buffer
isn't mapped. grow_dev_page does nothing because there are buffers on the
page with the correct size. madhav@veritas.com and others at Veritas
tracked this down.
The fix below has two parts. First, it changes __find_get_block to avoid
the buffer_error warnings when it finds unmapped buffers on the page.
Second, it changes grow_dev_page to map the buffers on the page by calling
init_page_buffers. init_page_buffers is changed so we don't stomp on
uptodate bits for the buffers.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'fs')
-rw-r--r-- | fs/buffer.c | 36 |
1 files changed, 23 insertions, 13 deletions
diff --git a/fs/buffer.c b/fs/buffer.c index 54c16cd28697b0..7a31850892cbb4 100644 --- a/fs/buffer.c +++ b/fs/buffer.c @@ -426,6 +426,7 @@ __find_get_block_slow(struct block_device *bdev, sector_t block, int unused) struct buffer_head *bh; struct buffer_head *head; struct page *page; + int all_mapped = 1; index = block >> (PAGE_CACHE_SHIFT - bd_inode->i_blkbits); page = find_get_page(bd_mapping, index); @@ -443,14 +444,23 @@ __find_get_block_slow(struct block_device *bdev, sector_t block, int unused) get_bh(bh); goto out_unlock; } + if (!buffer_mapped(bh)) + all_mapped = 0; bh = bh->b_this_page; } while (bh != head); - printk("__find_get_block_slow() failed. " - "block=%llu, b_blocknr=%llu\n", - (unsigned long long)block, (unsigned long long)bh->b_blocknr); - printk("b_state=0x%08lx, b_size=%u\n", bh->b_state, bh->b_size); - printk("device blocksize: %d\n", 1 << bd_inode->i_blkbits); + /* we might be here because some of the buffers on this page are + * not mapped. This is due to various races between + * file io on the block device and getblk. It gets dealt with + * elsewhere, don't buffer_error if we had some unmapped buffers + */ + if (all_mapped) { + printk("__find_get_block_slow() failed. " + "block=%llu, b_blocknr=%llu\n", + (unsigned long long)block, (unsigned long long)bh->b_blocknr); + printk("b_state=0x%08lx, b_size=%u\n", bh->b_state, bh->b_size); + printk("device blocksize: %d\n", 1 << bd_inode->i_blkbits); + } out_unlock: spin_unlock(&bd_mapping->private_lock); page_cache_release(page); @@ -1093,18 +1103,16 @@ init_page_buffers(struct page *page, struct block_device *bdev, { struct buffer_head *head = page_buffers(page); struct buffer_head *bh = head; - unsigned int b_state; - - b_state = 1 << BH_Mapped; - if (PageUptodate(page)) - b_state |= 1 << BH_Uptodate; + int uptodate = PageUptodate(page); do { - if (!(bh->b_state & (1 << BH_Mapped))) { + if (!buffer_mapped(bh)) { init_buffer(bh, NULL, NULL); bh->b_bdev = bdev; bh->b_blocknr = block; - bh->b_state = b_state; + if (uptodate) + set_buffer_uptodate(bh); + set_buffer_mapped(bh); } block++; bh = bh->b_this_page; @@ -1133,8 +1141,10 @@ grow_dev_page(struct block_device *bdev, sector_t block, if (page_has_buffers(page)) { bh = page_buffers(page); - if (bh->b_size == size) + if (bh->b_size == size) { + init_page_buffers(page, bdev, block, size); return page; + } if (!try_to_free_buffers(page)) goto failed; } |