From: Josef Bacik <josef@redhat.com> To: linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Cc: hch@infradead.org, akpm@linux-foundation.org Subject: [PATCH 1/5] fs: allow short direct-io reads to be completed via buffered IO V2 Date: Fri, 7 May 2010 13:39:48 -0400 [thread overview] Message-ID: <20100507173948.GB3360@localhost.localdomain> (raw) V1->V2: Check to see if our current ppos is >= i_size after a short DIO read, just in case it was actually a short read and we need to just return. 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. I also ran xfstests against xfs and btrfs with this patch and everything came out as expected. Thanks, Signed-off-by: Josef Bacik <josef@redhat.com> --- mm/filemap.c | 36 +++++++++++++++++++++++++++++++----- 1 files changed, 31 insertions(+), 5 deletions(-) diff --git a/mm/filemap.c b/mm/filemap.c index 140ebda..829ac9c 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 +1290,47 @@ 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; + } + + /* + * Btrfs can have a short DIO read if we encounter + * compressed extents, so if there was an error, or if + * we've already read everything we wanted to, or if + * there was a short read because we hit EOF, go ahead + * and return. Otherwise fallthrough to buffered io for + * the rest of the read. + */ + if (retval < 0 || !count || *ppos >= size) { file_accessed(filp); goto out; } } } + count = retval; for (seg = 0; seg < nr_segs; seg++) { read_descriptor_t desc; + loff_t offset = 0; + + /* + * If we did a short DIO read we need to skip the section of the + * iov that we've already read data into. + */ + 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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
WARNING: multiple messages have this Message-ID (diff)
From: Josef Bacik <josef@redhat.com> To: linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Cc: hch@infradead.org, akpm@linux-foundation.org Subject: [PATCH 1/5] fs: allow short direct-io reads to be completed via buffered IO V2 Date: Fri, 7 May 2010 13:39:48 -0400 [thread overview] Message-ID: <20100507173948.GB3360@localhost.localdomain> (raw) V1->V2: Check to see if our current ppos is >= i_size after a short DIO read, just in case it was actually a short read and we need to just return. 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. I also ran xfstests against xfs and btrfs with this patch and everything came out as expected. Thanks, Signed-off-by: Josef Bacik <josef@redhat.com> --- mm/filemap.c | 36 +++++++++++++++++++++++++++++++----- 1 files changed, 31 insertions(+), 5 deletions(-) diff --git a/mm/filemap.c b/mm/filemap.c index 140ebda..829ac9c 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 +1290,47 @@ 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; + } + + /* + * Btrfs can have a short DIO read if we encounter + * compressed extents, so if there was an error, or if + * we've already read everything we wanted to, or if + * there was a short read because we hit EOF, go ahead + * and return. Otherwise fallthrough to buffered io for + * the rest of the read. + */ + if (retval < 0 || !count || *ppos >= size) { file_accessed(filp); goto out; } } } + count = retval; for (seg = 0; seg < nr_segs; seg++) { read_descriptor_t desc; + loff_t offset = 0; + + /* + * If we did a short DIO read we need to skip the section of the + * iov that we've already read data into. + */ + 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
next reply other threads:[~2010-05-07 17:39 UTC|newest] Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top 2010-05-07 17:39 Josef Bacik [this message] 2010-05-07 17:39 ` [PATCH 1/5] fs: allow short direct-io reads to be completed via buffered IO V2 Josef Bacik 2010-05-18 21:05 Josef Bacik
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