[PATCH] async write errors: report truncate and io errors on

From: Oliver Xymoron <oxymoron@waste.org>

These patches add the infrastructure for reporting asynchronous write errors
to block devices to userspace.  Error which are detected due to pdflush or VM
writeout are reported at the next fsync, fdatasync, or msync on the given
file, and on close if the error occurs in time.

We do this by propagating any errors into page->mapping->error when they are
detected.  In fsync(), msync(), fdatasync() and close() we return that error
and zero it out.


The Open Group say close() _may_ fail if an I/O error occurred while reading
from or writing to the file system.  Well, in this implementation close() can
return -EIO or -ENOSPC.  And in that case it will succeed, not fail - perhaps
that is what they meant.


There are three patches in this series and testing has only been performed
with all three applied.

1 files changed, 7 insertions, 3 deletions

diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h
index 1f468b0491ed..33d0ce110034 100644
--- a/include/linux/buffer_head.h
+++ b/include/linux/buffer_head.h
@@ -24,8 +24,9 @@ enum bh_state_bits {
 	BH_Async_Read,	/* Is under end_buffer_async_read I/O */
 	BH_Async_Write,	/* Is under end_buffer_async_write I/O */
 	BH_Delay,	/* Buffer is not yet allocated on disk */
-
 	BH_Boundary,	/* Block is followed by a discontiguity */
+	BH_Write_EIO,	/* I/O error on write */
+
 	BH_PrivateStart,/* not a state bit, but the first bit available
 			 * for private allocation by other entities
 			 */
@@ -109,12 +110,14 @@ TAS_BUFFER_FNS(Dirty, dirty)
 BUFFER_FNS(Lock, locked)
 TAS_BUFFER_FNS(Lock, locked)
 BUFFER_FNS(Req, req)
+TAS_BUFFER_FNS(Req, req)
 BUFFER_FNS(Mapped, mapped)
 BUFFER_FNS(New, new)
 BUFFER_FNS(Async_Read, async_read)
 BUFFER_FNS(Async_Write, async_write)
-BUFFER_FNS(Delay, delay);
+BUFFER_FNS(Delay, delay)
 BUFFER_FNS(Boundary, boundary)
+BUFFER_FNS(Write_EIO,write_io_error)
 
 #define bh_offset(bh)		((unsigned long)(bh)->b_data & ~PAGE_MASK)
 #define touch_buffer(bh)	mark_page_accessed(bh->b_page)
@@ -139,7 +142,8 @@ void set_bh_page(struct buffer_head *bh,
 int try_to_free_buffers(struct page *);
 void create_empty_buffers(struct page *, unsigned long,
 			unsigned long b_state);
-void end_buffer_io_sync(struct buffer_head *bh, int uptodate);
+void end_buffer_read_sync(struct buffer_head *bh, int uptodate);
+void end_buffer_write_sync(struct buffer_head *bh, int uptodate);
 void end_buffer_async_write(struct buffer_head *bh, int uptodate);
 
 /* Things to do with buffers at mapping->private_list */