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* [PATCH 1/3] fs: allow short direct-io reads to be completed via buffered IO
@ 2010-05-03 16:11 Josef Bacik
  2010-05-03 16:11 ` [PATCH 2/3] direct-io: add a hook for the fs to provide its own submit_bio function Josef Bacik
  0 siblings, 1 reply; 7+ messages in thread
From: Josef Bacik @ 2010-05-03 16:11 UTC (permalink / raw)
  To: linux-btrfs, linux-fsdevel, linux-kernel, linux-mm; +Cc: Josef Bacik

This is similar to what already happens in the write case.  If we have a short
read while doing O_DIRECT, instead of just returning, fallthrough and try to
read the rest via buffered IO.  BTRFS needs this because if we encounter a
compressed or inline extent during DIO, we need to fallback on buffered.  If the
extent is compressed we need to read the entire thing into memory and
de-compress it into the users pages.  I have tested this with fsx and everything
works great.  Thanks,

Signed-off-by: Josef Bacik <josef@redhat.com>
---
 mm/filemap.c |   19 +++++++++++++++----
 1 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index 140ebda..cc804d9 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1263,7 +1263,7 @@ generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
 {
 	struct file *filp = iocb->ki_filp;
 	ssize_t retval;
-	unsigned long seg;
+	unsigned long seg = 0;
 	size_t count;
 	loff_t *ppos = &iocb->ki_pos;
 
@@ -1292,19 +1292,30 @@ generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
 			}
 			if (retval > 0)
 				*ppos = pos + retval;
-			if (retval) {
+			if (retval < 0 || !count) {
 				file_accessed(filp);
 				goto out;
 			}
 		}
 	}
 
+	count = retval;
 	for (seg = 0; seg < nr_segs; seg++) {
 		read_descriptor_t desc;
+		loff_t offset = 0;
+
+		if (count) {
+			if (count > iov[seg].iov_len) {
+				count -= iov[seg].iov_len;
+				continue;
+			}
+			offset = count;
+			count = 0;
+		}
 
 		desc.written = 0;
-		desc.arg.buf = iov[seg].iov_base;
-		desc.count = iov[seg].iov_len;
+		desc.arg.buf = iov[seg].iov_base + offset;
+		desc.count = iov[seg].iov_len - offset;
 		if (desc.count == 0)
 			continue;
 		desc.error = 0;
-- 
1.6.6.1

^ permalink raw reply related	[flat|nested] 7+ messages in thread
* [PATCH 1/3] fs: allow short direct-io reads to be completed via buffered IO
@ 2010-05-03 17:27 Josef Bacik
  2010-05-04  0:14 ` Dave Chinner
  0 siblings, 1 reply; 7+ messages in thread
From: Josef Bacik @ 2010-05-03 17:27 UTC (permalink / raw)
  To: linux-btrfs, linux-fsdevel, linux-kernel, linux-mm

This is similar to what already happens in the write case.  If we have a short
read while doing O_DIRECT, instead of just returning, fallthrough and try to
read the rest via buffered IO.  BTRFS needs this because if we encounter a
compressed or inline extent during DIO, we need to fallback on buffered.  If the
extent is compressed we need to read the entire thing into memory and
de-compress it into the users pages.  I have tested this with fsx and everything
works great.  Thanks,

Signed-off-by: Josef Bacik <josef@redhat.com>
---
 mm/filemap.c |   23 ++++++++++++++++++-----
 1 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index 140ebda..423b439 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1263,7 +1263,7 @@ generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
 {
 	struct file *filp = iocb->ki_filp;
 	ssize_t retval;
-	unsigned long seg;
+	unsigned long seg = 0;
 	size_t count;
 	loff_t *ppos = &iocb->ki_pos;
 
@@ -1290,21 +1290,34 @@ generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
 				retval = mapping->a_ops->direct_IO(READ, iocb,
 							iov, pos, nr_segs);
 			}
-			if (retval > 0)
+			if (retval > 0) {
 				*ppos = pos + retval;
-			if (retval) {
+				count -= retval;
+			}
+			if (retval < 0 || !count) {
 				file_accessed(filp);
 				goto out;
 			}
 		}
 	}
 
+	count = retval;
 	for (seg = 0; seg < nr_segs; seg++) {
 		read_descriptor_t desc;
+		loff_t offset = 0;
+
+		if (count) {
+			if (count > iov[seg].iov_len) {
+				count -= iov[seg].iov_len;
+				continue;
+			}
+			offset = count;
+			count = 0;
+		}
 
 		desc.written = 0;
-		desc.arg.buf = iov[seg].iov_base;
-		desc.count = iov[seg].iov_len;
+		desc.arg.buf = iov[seg].iov_base + offset;
+		desc.count = iov[seg].iov_len - offset;
 		if (desc.count == 0)
 			continue;
 		desc.error = 0;
-- 
1.6.6.1


^ permalink raw reply related	[flat|nested] 7+ messages in thread

end of thread, other threads:[~2010-05-04 23:07 UTC | newest]

Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2010-05-03 16:11 [PATCH 1/3] fs: allow short direct-io reads to be completed via buffered IO Josef Bacik
2010-05-03 16:11 ` [PATCH 2/3] direct-io: add a hook for the fs to provide its own submit_bio function Josef Bacik
2010-05-03 16:11   ` [PATCH 3/3] Btrfs: add basic DIO read support Josef Bacik
2010-05-03 17:27 [PATCH 1/3] fs: allow short direct-io reads to be completed via buffered IO Josef Bacik
2010-05-04  0:14 ` Dave Chinner
2010-05-04 15:27   ` Josef Bacik
2010-05-04 23:07     ` Dave Chinner

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